If your first reaction to “intermittent fasting with type 1 diabetes” is…”Oh my gosh, my blood sugar would be so low! I could never do that!” …then definitely keep reading.
In this guide, I will cover everything you need to know about intermittent fasting with type 1 diabetes:
Table of Contents
What’s the point of intermittent fasting?
There are 3 general reasons a person might want to pursue intermittent fasting.
- Weight-loss: This is the most obvious and most common reason to give it a try.
- Simplicity: Reducing the number of hours each day that you have to think about food, track food, make decisions around food, and cook food can be really freeing! Instead of frantically and unexpectedly skipping meals because of a hectic schedule, intermittent fasting allows you to properly and methodically skip eating during parts of the time.
- Energy: Once you get going, and you’re no longer freaking out about, “How hungry will I feel!?!”…this approach to eating can actually give you quite a boost of energy because your body will be burning fat for fuel instead of relying on sugar from your blood. Body fat is an endless source of energy.
Before we get started: if your blood sugar drops just because you don’t eat for a handful of hours, you’re taking too much background/basal insulin via pump or injection. Talk to your CDE or primary care doctor about “basal testing.” (Or check out Gary Scheiner’s book, ‘Think Like a Pancreas’ and do the basal testing yourself!)
Basal testing literally consists of purposefully skipping a meal (or two) in order to see if your insulin keeps your blood sugar steady, or if your blood sugar significantly rises or falls out of your personal goal range. If it rises, you’re not getting enough background/basal insulin. If it falls, then you’re clearly getting too much.
How intermittent fasting works
When you wake up with an in-range blood sugar (ideally between 70 to 130 mg/dL as a person with type 1 diabetes…the 130 mg/dL being on the higher end but offering some room for imperfection in a complex disease) and you don’t eat breakfast, which means you don’t take a bolus of insulin, your body will continue to burn fat for fuel because you have yet to introduce actual fuel. You have yet to turn on that switch telling your body to rely on glucose for fuel instead of fat.
The moment you eat or drink something containing calories, your body says, “Alright! Now it’s time to burn glucose!”
What an intermittent fasting schedule looks like
There are a lot of different ways you can approach fasting, and after doing this for several years on and off, I’ve found I can flexibly create my own approach that feels most natural to me.
Here are 3 of the most popular fasting schedules, adapted from Dr. John Berardi’s guide to intermittent fasting:
- 24-hour fast: You eat dinner on Thursday (for example), and then you don’t eat again until dinner on Friday. This should generally only be performed once per week. (Read Dr. Berardi’s guide to see what happens if you do a 24-hour fast too often.)
- 16-hour fast: You eat dinner on Thursday (for example), and then you don’t eat again until 1 or 2 p.m. the next day. It’s important to note that you should still eat a normal day’s worth of calories during that 8-hour eating window. If you’re trying to lose weight, that amount of calories might only be 1200 to 1600, but you still need to get your calories while following a fasting program.
- Periodic fast: You suddenly decide to go 24 hours without eating, unrelated to your fasting or eating schedule throughout the rest of week. I like using it when I know I’m going to be eating a really heavy meal (Thanksgiving, holidays, pizza or Chinese food, etc.). I’ve also used this when I know I’m going to be sitting in a car for a long time on a road-trip, or if I know I’m going to be somewhere new with my kids and I really don’t want to risk any low or high blood sugars – I just want to remove diabetes from the equation altogether so I’ll fast as long as I can that day.
If you search the web on intermittent fasting, you’ll find there are people who emphasize that fasting for weight-loss needs to coincide with very clean-eating and attention to nutrition, while you’ll find others who say they fast all day and then eat pizza every night.
If you’re trying to lose weight, you’ll really want to lean towards the clean-eating and attention to nutrition (with treat-days planned of course, for long-term success and adherence), but if you’re trying to maintain your weight, I think intermittent fasting offers a lot of wiggle-room for less healthy eating.
During the holidays, for example, I let my eating choices slide quite a bit compared to my normal routine, but I was still following a 16-hour or 24-hour fasting schedule most days of the week, so I didn’t actually gain weight beyond a little carb-laden bloating and water retention.
But won’t I be hungry?
Guess what, it’s okay to be a little hungry. After you stop freaking out about your belly not feeling full 24/7, and push through it around 10 a.m., you might actually notice that you feel a little bit awesome. A little more clear-headed, a little more focused, even a little more energy.
Drink some water – it’s good for you anyway – and embrace that feeling of your body just being empty. Yes, there are many ways to lose weight by eating every 3 to 4 hours, but that’s not the only way to eat, and it’s not the only way to lose weight.
Are you someone who is always thinking about their next meal? Always snacking?
As Dr. Berardi explains:
“Intermittent fasting can be helpful for in-shape people who want to really get lean without following conventional bodybuilding diets, or for anyone who needs to learn the difference between body hunger and mental hunger.”
But if you’re an athlete or intense exerciser...you might simply find that you really need that morning fuel because of your athletic pursuits! That’s okay! That just means intermittent fasting isn’t for you.
But isn’t eating breakfast really important?
Eating breakfast can absolutely be a crucial part of weight-loss and maintaining a healthy metabolism, but it’s not the only way, and more recent research has really diminished how important breakfast really is.
“There haven’t been any conclusive studies that found eating breakfast to have a positive effect on weight loss or weight maintenance,” explains sports nutritionist and registered dietician, Leslie Bonci, as reported in Popular Science.
Also, the idea that skipping breakfast causes weight gain is over-simplified and very false. It’s not the act of skipping breakfast that can cause weight gain, but that in those studies it’s observed that a large majority of those who skip breakfast also lack other healthy habits overall.
“It could be that eating breakfast is simply a marker of a healthy lifestyle and, in itself, doesn’t protect against obesity,” explains Science Alert.
“Several randomized trials (where people are randomly assigned to a certain behaviour, such as eating breakfast or skipping breakfast) have not found any evidence to suggest that skipping breakfast causes weight gain. Despite the association between skipping breakfast and weight gain, experiments specifically designed to try and establish cause and effect haven’t provided evidence that skipping breakfast causes you to put on weight.”
How to do intermittent fasting with type 1 diabetes
As a person with type 1 diabetes, you might even notice that you feel…a little free, because you aren’t worrying about whether you’re going to be high or low after your breakfast.
The awesome part of this for people with type 1 diabetes is this: your blood sugar is steady, steady, steady all morning long until you end your fast by eating at 11 a.m. or 2 p.m. or dinnertime…depending on which fasting schedule you follow.
I’ve also found that if I do a 24-hour fast before a carb-heavy meal like pizza, I’ve found that fasting actually cuts down significantly on the insulin I need for that meal.
If you stick to your fasting program consistently, you’ll find you lose weight and you gain insulin sensitivity, which means: you’ll need to decrease your background/basal insulin rates! This is a good thing! This is part of weight-loss with diabetes, but if you aren’t expecting it, you’ll be annoyed and frustrated with the low blood sugars.
How to adjust high or low blood sugar when fasting
Waking up with an in-range blood sugar is extremely helpful, but obviously, we’re not perfect and things happen. Here’s how to manage your plan for fasting if your blood sugar is not in your ideal range when you wake up:
- If you wake up a little high, sure, you can take a reduced correction dose (read ‘Think Like a Pancreas’ if you don’t know your own correction dose), and carry on with the fast, but introducing that bolus of insulin could be enough to switch on your body’s need to burn glucose for fuel. (For legitimate “dawn phenomenon” high blood sugars, you may simply need a bolus correction of insulin every morning that really is part of your “basal” insulin but is applied via pump or injection as a bolus. If this prevents morning fasting highs, it’s part of your fasting regimen!) *Read more about managing “dawn phenomenon” here.
- If you don’t take that correction dose of insulin, then you’re just spending the next several hours with a high blood sugar…which is counterproductive if our overall goal is health…right? So definitely take the insulin you need in order to be at healthy blood sugar levels–that’s your first priority.
- If you wake up low, then you obviously have to eat and fasting is no longer going to work. You’d be better off eating a healthy breakfast, fueling your metabolism since it’s already burning glucose for fuel, and trying again tomorrow.
- If you routinely wake up with blood sugars that are too high or too low, you need to go back and do some basal testing or test your insulin-to-carbohydrate ratios that you’re using for the food you eat before bed.
- Or this sneaky blood sugar problem: You need to stop binge-eating late at night. If you’re currently up at midnight eating yourself out of house and home, focus on this first before pursuing intermittent fasting. People often blame high blood sugars in the morning on “the dawn phenomenon” when it’s actually the result of late-night binge-eating.
It’s not a magic trick. It’s not a fad. It’s just basic science of how the body responds in a fasted environment.
Exercising in the Morning When Fasting…Is Actually Easier!
When you’re fasting during your exercise, your blood sugar isn’t going to burn up and drop–this is a good thing! Exercising while fasting (which means you did not just take a bolus of insulin for food or a high blood sugar) is easier because your body will burn body fat for fuel instead of glucose. I didn’t believe it either when I first learned this from the bodybuilders at my gym many years ago, but it works.
You will find that with weight-lifting or other anaerobic workouts, your blood sugar will possibly rise during a fasted workout, which means you might actually need a bolus of insulin for that type of workout. This will not take away from your fasted efforts, it simply helps use the glucose that’s being generated from the glycogen in your muscles being broken down due to your anaerobic workout!
I LOVE fasted cardio! In fact, I make sure that all of my exercise sessions happen either fasted in the morning or fasted in the evening (by not eating anything after 1 p.m. and then getting on the treadmill around 7 pm. This ensures that all bolused rapid-acting insulin is well out of my system. It works. When I used to lift weights, I did find that I needed 1 unit of insulin in the morning if I was doing a fasted weightlifting workout.
So in a nutshell:
- wake up with an in-range blood sugar (or correct a slight high with half of your usual correction)
- begin your workout while fasted
- check your blood sugar halfway through your workout during the first few experiments for safety’s sake
- if your anaerobic workout proves to raise your blood sugar, take half of what you would take to correct that high — but take it when you start exercising to prevent the high in the first place
- if your workout is aerobic (cardio), just continue your workout — you shouldn’t see a rise in blood sugar from aerobic fasted exercise
- check your blood sugar at the end
- shower (thank you)…and enjoy the rest of your fasting
Frequently Asked Questions
Is intermittent fasting safe for people with type 1 diabetes?
Absolutely! But you need to make sure your insulin doses and medications are properly tuned. For type 2s taking diabetes medications that intentionally lower blood sugar, you’ll likely want to talk to your doctor about taking that dose with your first meal versus “in the morning” if you intend to fast in the morning.
For type 1s, as discussed extensively above, your insulin doses should be finely tuned (even if you don’t ever plan to fast) so that you can miss meals and your blood sugar is generally steady and in a healthy range. Adjusting your insulin doses to meet this standard is called “basal testing.” If you’ve never done any basal testing to assess the accuracy of your personal insulin doses, definitely do that first. And do it even if you don’t ever intend to fast. It’s essential to diabetes management.
Again, as explained earlier, during your first week of fasting, check your blood sugar often during your fasting window to see how your body responds. And if you stick with it long-term, you’ll find you definitely will need to reduce your basal rates (even within a week or two) because intermittent fasting has an awesome benefit of…increasing your sensitivity to insulin!
What can you drink during intermittent fasting?
During the time-frame that you’re not eating calories, you shouldn’t be drinking any calories either. Black coffee or tea or water or seltzer (or diet soda, if you must) are all safe to drink. In general, I don’t encourage the consumption of drinks loaded with fake sweeteners. Drinks like Vitamin Water, even the sugar-free version, still contains calories. Read your labels carefully, and if all else fails, ditch the “diet” products for some all natural, chemical-free plain water!
Do you need to do intermittent fasting if you already follow a ketogenic diet?
You’re obviously going to be burning more fat than the rest of us after eating a ketogenic breakfast, but even some of that breakfast will be converted to glucose and require a bit of insulin to digest, so intermittent fasting still applies to keto-folks, too.
Adding fasting to an already disciplined ketogenic diet will definitely help your weight-loss progress.
Just beware, however, that if you don’t already understand how to eat enough on a ketogenic diet, adding fasting to the mix can be a recipe for a binge.
I highly recommend studying and practicing ketogenic eating for a few months before adding fasting to it. It’s very common for new low-carb eaters to eat too little because they are still afraid of eating too much fat. And fat, as you’ve probably heard, is a pretty crucial part of a successful ketogenic diet!
Why I love intermittent fasting as a mom
I can wake up in the morning, drink a cup of black coffee and guzzle some regular ol’ water, then pack our bags and head out the door to the playground or playgroup or the library. I can chase my kids around all morning long and I don’t have to worry about my blood sugar.
If I woke up at 90 mg/dL, I know my blood sugar is still in that zone.
I didn’t have to spend any time making my own breakfast. Or trying to find the time to make my own breakfast. I don’t have to worry about getting real, healthy food into my own belly until we come home from our morning activity, and I get the kids lunch and get everybody settled.
(If you’re not a mom of two children, let me tell you that finding time for your own breakfast is actually incredibly challenging some days amongst the diaper changes and the bottles and playtime and the…on and on and on! When that second kid pops out, parenting is ON in full-power-mode 24/7.)
By 1 or 2 p.m., I’m not starving, I actually feel pretty energized after that morning fast. And making myself a healthy meal feels very doable because the busiest part of the day is behind us.
Should you try intermittent fasting?
If all of the above sounds appealing to you, give it a try!
A few things to keep in mind when trying intermittent fasting with type 1 diabetes:
- Do you currently have a healthy relationship with food? If not, I would address that first. Fasting is not ideal for the yo-yo dieter or someone trying to recover from an eating disorder. Visit We Are Diabetes or check out my book on Emotional Eating with Diabetes or Diabetes Burnout to get started.
- Take good notes! The first week you try fasting, write down the insulin you took before bed, what your blood sugar was in the a.m., etc., so you can pinpoint any diabetes-related variables that are causing lows or highs in your blood sugar during the fasting period. For example: if you’re still up at midnight eating chips and ice cream, you can absolutely bet that will raise your blood sugar during the hours of 6 a.m. to 12 p.m. when you’re fasting. Some people blame dawn phenomenon for what is actually late-night binge-eating.
- During the first few fasts, check your blood sugar often. Even though fasting itself shouldn’t cause low blood sugars, your insulin doses simply might not be accurate! And nothing will reveal that sooner than fasting. Check your blood sugar often and take good notes. Learning how to study and adjust your insulin doses is a crucial part, I believe, of long-term success in life with type 1 diabetes.
- It doesn’t have to be 100% to benefit you: If I wake up and feel really hungry and genuinely feel an intense need to eat, then I listen to my body, and I eat breakfast. If I want to go out to breakfast (once in a blue moon) with my family, then I eat breakfast. It’s not a big deal! Make it work for you. Follow the program as much as you can, and don’t freak out when life gets in the way.
- You may find it useful for a few months, then back to a normal schedule. I’ve found that intermittent fasting has been really wonderful for me for several months at a time. And then I take a break from it for a couple of months, and then I naturally feel ready to follow that schedule again. Listen to your body and find what works for you.
- Be patient. If you fail a day of fasting because you gave in and ate one of those goddamned office muffins, relax. I’m a big believer that creating your own life around nutrition is a very long work in progress. Be constantly open to evolving, learning, trying new things, and never never never shaming yourself for being imperfect. It’s one big science project. Enjoy the project, stop punishing yourself, and learn to love the food you eat. Food can be fun, even when you’re trying to lose weight!
Learn. Study. Experiment. Repeat!
Update: I recorded this video where I talk more about why I do fasted cardio, how I do it, and the benefits. Please let me know what you think in the comments below
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Christina W. says
May 29, 2019 at 1:10 pmI am 42 and have had Type 1 most of my life. I recently discovered Intermittent Fasting and I LOVE IT!! I do a 16/8 plan, so I eat between noon to 8 pm each day and fast from 8 pm to noon. It was a total experiment, but my results so far:
1) The best, most stable blood sugars of my LIFE! I can’t wait to get my next A1c test!
2) I have way more energy and mental clarity. After struggling with chronic fatigue/ brain fog for 10 years, this is a miracle for me. I feel amazing!
3) Depression— GONE.
4) I have lost 12 lbs of pure body fat, while still building muscle and feeling stronger and stronger. None of my pants fit and even my undeez are baggy! I seriously look better than I did 10 years ago.
Thank you for your super great article on IF with Type 1! Your recommendations are spot-on with my experience. Type 1’s can TOTALLY fast if we do it safely (I have done up to a 4-day fast at a spiritual retreat and it went great too). To your health! 😁
Christina W. says
May 29, 2019 at 1:13 pmI forgot to say… these results are after about 2 months of IF. Drink plenty of water/tea while fasting because dehydration raises blood sugar 😘
Janira says
June 10, 2019 at 7:14 amCongratulations on your results Christina. I was just curious, do you fast daily or a few times a week, what schedule do you find helpful?
Marc says
June 18, 2019 at 6:06 amI also just started IF 2 weeks ago. I have been a T1D fo 48 years. I have experienced the most stable blood sugars in my life. I believe it really helps if one is on a pump and CGM. I have adjusted my overnight basal insulin as I was covering for my late night snacks. My overnight blood sugars are almost a straight line and the dawn phenomenon is gone.
Melissa says
May 27, 2019 at 6:26 amHi Ginger,
I am a shift worker. I often work 2 – 12 hour days, followed immediately by 2 – 12 hour nights. I have a basal rate programmed for each of those shifts. I’m having difficulty on my “switch over day” (going from my second day to my first night), as I’m still up at 7 or 8 am, then up all day. I continue to fast until 12 or 1pm, but am not sure how safe it is to not eat anything while I’m at work. Also, during work I do get hungry, as it can be a physically demanding job.
So I do my normal fast during that day, but then I eat something small during night shift to get me through… but then I sleep during the day.
I guess I’m not sure how my eating window’s fit in during my work week and switch over day, and is it ok to be eating in the night? Or should I eat before I go to sleep after nights? This is all a little confusing to me.
Thanks for your insight!
Melissa
Ginger Vieira says
May 28, 2019 at 7:57 amHi Melissa!
Wow — that is a complex schedule!
I think you definitely have to create your own fasting routine because of your complex schedule.
But also: you don’t need to fast EVERY DAY to get the benefits. If there’s a couple days where it just doesn’t work because you’re eith er eating or sleeping, then just listen to your body and focus on making good food choices.
Is that helpful? Let me know what you think!
Selin says
May 26, 2019 at 6:43 amHi! I have type-1 diabetes for nearly 11 years, but it wasn’t going very well. Now I am trying different approaches to lower my hba1c. It’s been 2 weeks I started IF, my blood sugar at night is fantastic, but my blood sugar when I am in the eating window is way too high, even though I consume nearly 80-90 gr carbohydrate per day (generally not more than 30 per one meal). Is there a possibility that IF raises insulin resistance in the eating window, or body’s sensitivity to absorb carbohydrates?
Ginger Vieira says
May 28, 2019 at 7:58 amHI Selin!
Most likely, that’s just your liver releasing glycogen to compensate for not eating. VERY normal and happens in everybody (including me!) I have to take a bolus of insulin (about 1 to 2 units) mid-morning if I plan to fast until 2pm to compensate for that glycogen from my liver. It’s just your body’s way of dealing with not getting food.
You may also find that your body needs a little more insulin with your meals simply because all of your calories are being consumed within a smaller frame of time. Again, super normal!
Let me know if that’s helpful!
Ginger
Lancy says
May 17, 2019 at 3:46 pmThank you,will definitely start.
Diana says
May 17, 2019 at 10:11 amHi Ginger
I am a type 1 diabetic since I was 28 (now 42) and I am a mom of 2 active boys (so I understand your relief in not having to worry about your BG when you are busy with them)! I just started IF a couple of weeks ago and I fast from sometimes 7pm/ most times 8pm until 1pm, I am also on the mini-med 670g pump and have a CGM that communicates with the pump. So the 670g has an “auto mode” which automatically gives you basal as your BG increases… I only have to worry about giving myself a bolus when I eat. I am worried that because I am getting very small automatic doses of fast acting insulin (as basal) that IF would not work for me… should I be worried about that? Will I still be able to burn fat on this? Thank you for your help!
Ginger Vieira says
May 18, 2019 at 4:53 pmDiana! Don’t worry one bit. Your pump is simply compensating for the natural response from our liver when we skip breakfast: releasing glycogen. As someone who takes injections, I actually give myself a shot of 1 unit fast-acting insulin to compensate for this. You’re getting yours in smaller drips from your pump. The first priority is blood sugar management, and that’s what your pump is doing for you, keeping you in your goal range!
Jeanette says
June 8, 2019 at 4:47 amThank you as this is my situation also. I really appreciate all this information.
Joan Duncan says
May 30, 2019 at 3:57 amDiana, I’m also on a 670G and CGM. I’m 58 and been Type 1 since 2 1/2. I don’t have my system fine tuned like Ginger says but I have been using Mosley/Spencer the Fast Diet for a few years and love it! So far the best system my Doc has come up with is to do a Temp Target so BS stays @ 150 for a number of hours. Two days a week, I eat about 500 calories for the day and fast between breakfast and dinner. I’ve lost almost 20 lbs and find this is something I feel I can do the rest of my life. My TDD has gone down 10 units. If anyone else has found an Endo that works with you and believes in IF, I’d love to know about it!
Joan Duncan says
May 30, 2019 at 4:03 amforgot to thank you Ginger for this piece. So gratifying to connect with someone finding their own way and sharing with all of us in such a knowledgable manner! I’m very grateful.
Yogananda says
May 3, 2019 at 11:56 pmHi Ginger,
I am Type1 diabetes, want to be on fasting monthly once preferably 16 hrs fasting. I am from India and how can I be able to manage insulin and fasting. Typical blood sugar fasting remain be 120-140mg/dl whereas PPBS will be around 120-160mg/dl. HbA1C is around 7.8. what would you recommend.
Ginger Vieira says
May 5, 2019 at 9:39 amHI Yogananda,
I’m not quite sure what you’re asking but it sounds like your blood sugars are trending a little higher than ideal if your HbA1c is at 7.8. I would schedule an appointment with your diabetes educator (or work with one via Skype — like Jennifer Smith at IntegratedDiabetes.com) to help adjust your insulin doses to bring your BGs down. An A1c of 7.8 actually translates to an average blood sugar of 177 mg/dL, not 120-140. Before taking on intermittent fasting, I would focus first on studying your blood sugars/nutrition/insulin/activity to help improve your diabetes. Let me know what you think!
Cecilia Vieira Stone says
April 29, 2019 at 5:04 pmHi Ginger!
Amazing article, I have been wondering if IF was possible for one of my kids with Hashimoto’s, Celiac, and T1D, but was unsure if it was safe. Did IF cause a decrease in your A1C levels? I’m assuming it would if you start spending more time in a good range through the fasting hours, but wondering what your thoughts are on that from experience.
Thanks,
Cecilia
P.S. I’m a Vieira too, by the way–maiden name! (:
Chris Wo says
May 29, 2019 at 12:48 pmHi there… I’m not sure how old of a “kid” you’re talking about, but IF would not be recommended for a child/teen who is still growing. If obesity is the concern, I think that healthy eating and daily exercise would be better for a child/teen than fasting. Check with your doctor!
Zoe says
April 29, 2019 at 7:15 amHi Ginger,
I found this article really helpful! I am type 1 and just starting to Intermittent fast. One thing I have been concerned about is taking my non-insulin medications (Metformin/Spironolactone) on an empty stomach. I need to take both medications twice a day 12 hours apart. Fasting from 8pm-12pm is what I would like to do, but I am worried that the medications will make me sick if I take them on an empty stomach. Do you have any suggestions?
Thanks!
Zoe
Ginger Vieira says
April 30, 2019 at 8:22 amHi Zoe!
So, the first thing I would do is ask your doctor if you can adjust the timing of those medications so you take them with your first meal around 12 pm. — BUT then that means you’d be taking your second dose at midnight…which isn’t ideal.
Alternatively, you could keep your medication schedule as is and add some ZERO carb food like cheese or an egg to soak up the meds. Not perfect fasting, but not causing your body to burn glucose for fuel since you wouldn’t be eating any carbs.
This medication with food/12 hours apart is certainly a tricky obstacle!
Ginger
Kendall Barone says
March 25, 2019 at 8:11 pmHi!! Thank you for this great article. I am 22 years old and have been a Type 1 diabetic since I was 2. I have tried to do intermittent fasting but have noticed that I run low during my fast which breaks it. I eat between 11am – 7pm. And I workout around 5pm. I give my basal at 8:30am and with a healthy diet am needing to give very little insulin throughout the day now. However, I notice that after I work out at 5pm, (I eat around 630pm), I run a little high but do not give any insulin because I am always come back down and am waking up low around 3:30am. Any insight would be helpful 🙂
Ginger Vieira says
March 26, 2019 at 8:55 amHi Kendall!
If you’re running low during a fast, then you’re likely getting too much background (basal) insulin via pump or your long-acting insulin dose. Our background insulin needs change throughout our life, so it sounds like yours might need a slight reduction. Even a 1-unit reduction can make all the difference. Definitely talk to your healthcare team if you need help thinking through this dosing adjustment!
The opposite goes for your evening meal/workout. Are you pre-bolusing your insulin dose? If you’re eating and taking your insulin at the same time, you can expect that your blood sugar will rise and then eventually come down as the insulin starts to do its job. Pre-bolusing means taking your insulin 10 to 15 minutes before eating to reduce that post-meal spike. I highly recommend reading Think Like a Pancreas to learn more about this!
However, you also mentioned waking up low at 3:30am, which again means you’re getting too much background insulin OR too much insulin with the last meal you eat before bed. Adjustments adjustments adjustments. Our insulin needs change throughout our life! Consistent lows and highs means your dosing needs to be adjusted. Here’s another article to further learn about signs that you need to adjust your insulin: https://diabetesstrong.com/5-tips-to-lowering-your-a1c/
Let me know how it goes! And as always, I’m not your doctor…so talk to your healthcare team about making adjustments!
Megan Doumit says
March 7, 2019 at 9:55 pmHi Ginger!
Thanks for all this info! I am very intrigued by IF and want to give it a try. My question involves shift work. I work nights (6p-6a) 3 days a weeks, but keep regular hours on my days off (up by 8a, bed by 10-11p). Would IF still be effective if the time of my window changed? I was thinking of having my window be 12-8p on days off, 4p-12a on work days. Or should I just try to keep it the same for work and non-work days? I use an insulin pump that has automatic adjusting basal rates (I also wear a glucose sensor), which is super helpful with flipping back and forth.
Ginger Vieira says
March 9, 2019 at 5:07 amHi meagan!
Great question.
1. YES, you should and can absolutely adjust your fasting schedule based on the real life details of your unique job schedule.
2. You also don’t need to fast every single day. You could fast on certain days and not on others. For instance, people with small kids might not fast on days where they have their kids with them the whole day because patience runs extra thin when you haven’t eaten! Adjust as you see fit for you!
Jen says
February 10, 2019 at 8:32 amI just have to say thank you for this article. It’s been very helpful.
I have a question about fast timing. I am on multiple daily injections. In the evening, I will stop eating at 6:00pm, however I’ll notice around 8- 9:00pm I’ll need a second bolus to correct my BG from going up. After this bolus, I head to the perfect range and stay there till I break my fast the next day – 16 hours from when I started eating. Should my fast technically not start until that second bolus? My goals in using this tool are to be able to workout in the morning without going low (which is working!), loosing about 8lbs, and to not worry about anything BG related for a period of time. I am also a busy mom of two kids, and could completely relate to your story! It’s been amazing not having to think about about my BG when I’m running around with my kiddos.
Ginger Vieira says
February 11, 2019 at 11:14 amHey Jen!
Don’t worry about that 2-hour window. You’re simply doing what a non-diabetic’s body would do. Like a non-diabetic, count your fasting based on the last time you ate. All those extra injections we have to take are just meeting our insulin needs that a non-diabetic’s body is doing on its own!
Let me know how it goes!
Marianne says
February 7, 2019 at 3:08 pmAmazing article! Also enjoyed reading the comments and answers there. I love IF for several reasons, but I’m super frustrated about my dawn phenomenon and insulin resistency. I need about 40 units of insuline EVERY MORNING just to get back in the good range, and use 70 units of toujeo before going to bed, plus bolus with humalog during the day. Even on lowcarb, I’m easily on 200 units of insulin in total for 1 day. I feel great on IF both mentally and physically and my a1c dropped from 6,6 to 5,7 but after almost a year of doing IF I still need massive doses of insulin and my weight is also incredibly difficult to control. I’m getting so frustrated and really don’t know what to do anymore…
Ginger Vieira says
February 7, 2019 at 6:21 pmMarianne!
How long have you been on Toujeo?
Personally, Toujeo was a nightmare for me and for many others after the first month or two. My blood sugars were all over the place.
If you’re taking 40 units of fast-acting just to keep your BG down in the AM, then your background insulin is either in desperate need of a tune-up OR it’s simply not doing its job.
I’m not your doctor…but if I were you, I’d see how things go on Lantus or Tresiba. Toujeo is really iffy for man.
Regarding overall weight-loss, etc. — is there space within your overall nutrition choices/intake that could use a tune-up? If you’ve never worked with a professional (Christel at DiabetesStrong or Daniele at DiabetesDominator) to truly learn about nutrition for weight-loss goals, it’s worth every cent.
I learned from coaches 13 years ago! It’s worth it.
Holler back with further questions!
Alys says
February 4, 2019 at 12:44 pmHello. What an interesting article. I’m looking into intermittent fasting as I am looking to lose some weight. I have a few questions if you don’t mind…. I suffer from the common issue of dawn phenomenon so every morning I need about 2 units of fiasp fast acting insulin to meet the rise in glucose. Also I am a very active person and go to the gym 6 days a week. The issue I have is my excersises are quite intense and often include HIIT or weight training. Both of which cause a rise in my blood sugars so I need to take small correction doses before my workouts. Anyway my question is will these minimal correction units be enough to take my body out of fat burning mode even though I wont be consuming any calories?
Many thanks:)
Ginger Vieira says
February 4, 2019 at 3:19 pmAlys! I actually have the exact same two BG issues that I take boluses for as well. (Although, when I was on Tresiba, I didn’t need a morning bolus, but on Lantus, I do.) Anyways, don’t worry about. These are still part of your essential background insulin needs. You may find though that you need LESS of a bolus for your dawn phenomenon if you’re exercising (cardio) without eating. So I’d start with a 1/2 dose the first time you try it.
I definitely recommend reading some of the other comments/answers on here, too, because many others are in the same boat! Keep doing what you know keeps your blood sugar in your goal range and put Intermittent Fasting on top of that.
Mili Campo says
January 24, 2019 at 7:22 pmHi Ginger!
I would like to start by thanking you for all this knowledge you are sharing with us!!! It’s really hard finding information about fasting and Type 1 diabetes, it’s very frustrating. I wanted to consult something with you and would love your insight about it. My husband and I started intermittent fasting a couple of days ago. I feel awesome, but my husband (type 1 diabetic) has been having a high blood sugar after eating the first meal (around 250) even though his blood sugar during the day has been good (between 90-115) do you know what can be causing this? We tend to eat a big healthy dinner and a couple of snacks. Thank you again! God bless!
Ginger Vieira says
January 25, 2019 at 12:06 pmHi Mili!
Fortunately this sounds like a simple issue: he just needs more insulin with his meal. If his blood sugars are steady during the fast, his background insulin doses are great. But his post meal dose is clearly not covering his needs. Fasting might be causing him to need a little more than usual with his first meal — doesn’t really matter, either way it’s clear he just needs to increase his insulin-to-carb ratio or add the number of units he’s taking to correct that high BG to his initial meal dose! Let me know how it goes!
Marc says
January 17, 2019 at 7:43 amHello and thank you for your article! (which is probably the only content about this topic in the whole internet)
Does intermittent fasting really work with diabetes type 1? What about the basal insulin rate? Doesn´t that mean, that we all have always a specific amount of insulin in our body? Which amount of insulin in the body are necessary for not burning fat anymore..? These are the main questions I have to this topic. I hope, you understand, what I mean..? 🙂
Thank you!
Marc from Germany
Ginger Vieira says
January 17, 2019 at 12:10 pmHey Marc!
Valid questions.
Even non-diabetics always have insulin present in their bloodstream — that’s what keeps them alive! Every mammal needs insulin present. What throws your body into burning glucose for fuel rather than body fat is when you eat breakfast and your pancreas (or your pump/pen) delivers a large bolus of insulin.
I can tell you personally that intermittent fasting works very well in type 1! It helped me lose postpartum belly fat. And it always just minimizes the amount of time we have to think about food!
Now that I’m back on Lantus as my background insulin, I do find I have to take a small bolus of insulin in the morning if I’m going to fast, otherwise, my blood sugar will rise from the liver dumping glycogen. No big deal. I still continue my fast and reap the benefits!
The benefits of fasting also give your digestive tract a break — which has shown in many studies to improve several aspects of health and even lengthen your life!
Read through some of the other comments and questions below, too. We discuss this same topic in different ways!
Marc says
January 24, 2019 at 11:33 pmThank you so much for your answer, which helps me a lot! (Also your articel about the Dawn Phenomenon)
I´ve tried a basal rate test combined with a 24h fast, which worked very well with 23 units of Lantus, but there was a short hypo in the morning, followed by a very small Dawn Phenomenon, normal blood sugar the whole day and finaly a hypo after 22 hours.
Yesterday evening I took 22 units. I woke up this morning with 95, the Dawn Phenomenon boosted my sugar level to 220 in only 45 minutes. Now I took 2 units of bolus. So this is Ok for the body to stay in fat burning modus? 🙂
Ginger says
January 25, 2019 at 12:08 pmYup! I have to take a 1-unit Bolus in the morning too when I’m on Lantus and fasting. You’re still just covering glucose from your liver, not food you’re eating, which means it’s your background insulin needs. Our first priority is healthy BGs, and taking adequate insulin. Don’t worry about the tinier details we can’t control. Sounds like you’re a fasting pro!
Lyndsay says
January 13, 2019 at 6:49 amI take lantus in the morning and night. Should I still take my morning dose at the usual time or wait until I break my fast?
Christel Oerum says
January 13, 2019 at 11:49 amYour basal shouldn’t be depending on when you eat. However, Lantus does have a spike so if you find you go low you could try pushing it out. Generally changing to doses is recommended that you discuss with your doctor
Christy Pinsart says
January 5, 2019 at 11:43 pmMy hubby is really into Int. Fasting and I have been trying to find a way to do it. Being a type 1 diabetic for 38 years on pump, we could not make sense of it. I’m definitely going to show him this and try it!!
Judy Provence says
January 4, 2019 at 5:46 amHi Ginger,
I found your comments to be exceedingly helpful to me as I am a type 1 diabetic on an insulin pump and want badly to start fasting correctly. Everything you posted makes so much since to me and you answered several of my questions and concerns about fasting.
Do you have any books about fasting with Type 1 diabetes that you could suggest for a 68 year old woman (me)?
Thank you, Judy
Ginger Vieira says
January 4, 2019 at 11:41 amHi Judy! As far as I know, this article is the most in-depth published writing on fasting with type 1 diabetes. However, I wouldn’t be surprised if Sheri Colberg’s upcoming new version of her old book includes some text on fasting. I wrote this article because there isn’t anything else out there that offers in-depth guidance on the subject of fasting! If you find something, please let us know!
Dave says
November 21, 2018 at 4:28 amHi Ginger,
Just wondering about ‘breaking the fast’. In one of your articles you said that taking a bolus in the morning to counteract a high morning sugar could actually break the fast, as it will stimulate the body to use glucose as energy again instead of fat. I am doing 16:8 but often have to do this, despite increasing my basal, which I don’t want to increase anymore as it causes low sugar in the afternoon if it’s too much.
Does the fact that you have a sugar of say 9 mmol/l in the morning, with the background basal, mean that you cannot go into fasting mode to metabolise fat? This would make sense to me because there is excess blood sugar and basal insulin breaking it down, so why would you need to burn fat? As I understand it fat is only metabolised as a last resort once all excess glucose has been used? This would mean that bolus injections do the same, and prevent fat from being used as energy?
Many thanks for your help with this., Dave, London UK
Ginger Vieira says
November 21, 2018 at 10:57 amHi Dave!
Great question — we’ve talked about this in some other comments on this article too. Here’s the gist I can best explain, if I’m understanding your question correctly:
1. Our first responsibility as people with diabetes is to manage our blood sugars as safely and healthily as possible. Would we burn more fat if we ignored at 9mmol blood sugar and just kept fasting? Sure. But you’ll still benefit from your fast by taking a small correction dose, getting your blood sugar back to your goal range, and continuing your fast.
2. There are other benefits to fasting besides burning fat. It gives your digestion system a major break, and has shown in a lot of studies to actually lengthen our lives! There’s more — google for more and you’ll find it. BUT that being said, you can still burn fat while insulin is present, it’s just that when a large bolus of insulin is present, that fat-burning mode isn’t going to be primary anymore. For me, that’s about 1 unit of insulin — but I’m 5’2 and 120 lbs. If you’re a guy at 200 lbs and 5’11, 1 unit might not be as much relatively speaking in your body.
3. Personally, if I wake up with a 200 mg/dL, I would take a 1/4 unit (instead of 1 full unit) because I know I’m about to get a ton of exercise walking my dogs so I don’t need a full correction.
Does any of this answer your question?
The nutshell: we are people with diabetes BEFORE we are intermittent fasting fans. Healthy blood sugar levels come first, but just because you have to take a bolus of insulin to correct a high doesn’t mean your fast is completely ruined and pointless. You’re still not eating food and you’re still going to burn far more body fat than if you had eaten breakfast.
Dave says
November 23, 2018 at 4:48 amHi Ginger,
many thanks for your reply!
I will continue to give a bolus if it is needed then, because as you say, it is only a small dose and I can then continue with my fast.
I’ve been doing IF for 2 weeks only, but so far have gained 1kg in weight! Hopefully it will improve..
Im curious how you know that 1 unit of insulin if the amount to cause your energy mode to be glucose rather than fat – is this based on a formula, or is it just what feels right?
Thanks again for your help, it’s nice to discuss these things.
All the best, Dave
Erin B. Larsen says
June 17, 2019 at 9:39 amMy name is Erin. I am a type 1 diabetic. Right now my HBA1c is 6.1. I do take more basal insulin than bolus. In the last few weeks I have been able to go down a little bit, but when I lessen it anymore my blood sugars are noticeably higher. I am also doing both weighted cardio and lifting weights about 4-5x per week. I also have PCOS. Which intermittent fasting schedule would you suggest? I guess I should probably talk to my doctor about testing for my basal rate.
Ginger Vieira says
June 17, 2019 at 5:42 pmHi Erin!
I wouldn’t worry too much about making sure your bolus and basal insulin doses match. I think that applied much more to older insulins (NPH and Regular). I often take far more bolus insulin than my basal (for example). The most important thing is: are your blood sugars in your goal range? Are you taking so much bolus insulin because you’re constantly correcting highs?
It really sounds like you’re on a very healthy amount of insulin. And with an A1c of 6.1, it sounds like you’re doing an awesome job managing your diabetes!
For ANYONE interested in starting intermittent fasting, I’d recommend trying to do one or two days in one week where you skip breakfast (check blood sugar to keep an eye out for morning highs from liver dumping glycogen to compensate for no breakfast)…and eat your first meal around 1pm. This is the 16/8 hour schedule.
But again, it sounds like what you’re already doing is working great for you!
Let me know what you think!