Few things are more frustrating than having to stop your workout to treat a low (or high) blood sugar. It can be absolutely “I want to cry and throw a tantrum” frustrating!
The good news is that it’s possible to prevent most of these episodes. It takes practice, a lot of trial and error, and the right knowledge, but it can be done!
With practice, you should be able to go for a run or take a Zumba class without having to fear hypoglycemia (low blood sugars) or “carb up” beforehand. You should also be able to do a hardcore interval training class without seeing your blood sugar go through the roof.
I am not saying that you will never go low during a workout again after reading this post. I teach people with diabetes how to work out safely and effectively for a living, and I still have to cut a workout short because of my blood sugar sometimes. What I am saying is that if you implement everything you are about to read, you should soon have the confidence to never let your diabetes hold you back from exercising and living an active and healthy lifestyle.
This post is designed to be almost like a table of contents. Covering every aspect of exercising with diabetes is not possible in a single post, so each section of this post includes a link to more in-depth “how-to” information on managing your blood sugar. I suggest that you follow each link when you get to it, read the “how to” post, and then come back here.
It’s a lot of information (more than most people, myself included, can read or digest in one sitting), so just take it slow and think about how you can use each piece of information to optimize your diabetes management routine around workouts. You can always bookmark this post and refer back to it later.
Now, let’s get started!
Managing your blood sugar during steady-state cardio
When you do steady-state cardio, your heart rate is elevated and stays at about the same level throughout your workout. Examples of steady-state cardio are brisk walking, running or jogging in flat terrain or on a treadmill, biking on an exercise bike, and running on an elliptical machine.
For most people living with diabetes and taking insulin or type 2 drugs like Amaryl or Prandin (the sulfonylureas and meglitinides classes of drugs), steady-state cardio will lower their blood sugar and increase the risk of exercise-induced hypoglycemia so medication doses will have to be adjusted accordingly.
If you do less than 60 minutes of steady-state cardio, you generally don’t need to eat additional carbs to compensate for the workout if you have adjusted your insulin correctly. The trick is to plan ahead and adjust your insulin and food in good time before the workout.
For a detailed description of how to manage your blood sugar during steady state cardio, read the article “How to Prevent Low Blood Sugar during Cardio Workouts” by type 1 diabetic and triathlete champion Cliff Scherb (and be ready to take notes, this is good stuff!).
The advice in the link above is primarily for people using insulin. If you take other blood glucose-adjusting medications, please discuss medication adjustments with your medical team before starting a workout routine.
Managing your blood sugars during interval training
If you’re into boot camp classes, CrossFit, or similar types of workouts, you may have experienced that your blood sugars start spiking halfway through your workout, or maybe even right after. This type of cardio, where your heart rate goes from low to extremely elevated and back again several times during the workout, is called interval training.
The reason for the increase in blood sugar is that the improved insulin sensitivity from exercising is surpassed by your body’s glucose production. Your body is producing glucose faster than you can use it!
Completing an interval cardio session just to take more insulin to get your blood sugar down again can seem counterintuitive if you’re looking to lose weight, but that’s not necessarily the right way to think about it. Although you may have to correct an increase in your blood sugar during or right after your workout, that correction is not due to extra calorie consumption, so it doesn’t impact your daily calorie budget. Assuming you don’t overcorrect, the extra insulin won’t lead to weight gain. I like to think of it as glucose recycling.
You can read more about the science behind interval training and blood sugar in my post “Why Some Types of Exercise Can Make Your Blood Sugar Increase”.
Because I know that interval training won’t lower my blood sugar, I don’t reduce my insulin before an interval workout. I may even take a little extra insulin if my blood sugar is at the high end of my range before the workout.
Finding your exercise and diabetes formula
We all have different insulin sensitivities and we react differently to various types of exercise. The general rules described above (steady state cardio will lower your blood sugar while interval workouts won’t) apply to most people, but to successfully manage your diabetes when exercising, you need to find the specific formula for food and insulin (or type 2 drugs) that works for you.
To limit the risk of high or low blood sugars as a result of exercise, you have to do the upfront work and figure out your patterns. It’s not that hard, but it does take some time and dedication. I’ve written a detailed guide on “How to Find Your Formula for Insulin and Food Around Workouts” that I suggest you read and follow.
Basically, finding your formula comes down to:
- Reducing the number of variables
- Testing your blood sugar often
- Taking detailed notes and analyzing the results
You can use the Blood Glucose Tracker in the post I linked to above to log your workouts, food, and medication, so you can start finding your patterns and the formula that works for you!
Most importantly, you have to accept that you won’t get it right every time. There is no such thing as “perfect” diabetes management. This means that every time you start something new, you have to adjust (not restart) your formula. But trust me, the upfront work and the occasional missteps are worth it. Imagine walking into a gym or going for a run knowing that you got this (with glucose tabs in your pocket, just to be safe). It’s a good feeling 😀
Now, let’s do this!
Suggested next post: How Resistance Training Affect Your Blood Sugar
Ciccone
My brother is facing a lots of prblm because of diabetes. He is only 29 years old and his weight is 43 kg.
Taking Insulin on daily basis ..please let me know what can we do for him
Christel Oerum
If he’s eating enough but not gaining weight he might be taking too little insulin for his body’s needs. I’d direct him to resources that can help him decide how much inulin to inject for different foods. That education should be given by a medical professional. To get ready for the meeting with a medical professional he can read up on the following articles:
https://diabetesstrong.com/carb-counting/
https://diabetesstrong.com/insulin-to-carb-ratios/
Prem kumar
Hey Christel,
I just started reading your blog and find many of your answers quite interesting. My sugar fasting and pp sugar were around 110 and 120 respectively but onces I have started with resistance training 3 times a week my fasting reading have increased to 130 and pp reading to 140. Can you tell me why it is happening with me and should I avoid resistance training?
Christel Oerum
Usually, resistance training will increase your insulin sensitivity. I can’t explain why you seem to become (only slightly) more resistant. Maybe you changed your eating patterns along with your training? Regardless, I’d keep an eye on it and discuss it with your doctor
Nirali jain
Hi, chirstel love your every post. Keep sharing such valuable content. Because it helps millions of people to be fit.
Giselle
Hi Christel
thanks for the info – very interesting. About spiked glucose readings after interval training….in general – if it is high after working out – but later gets back into a normal level – and overall A1C levels are good – is a high reading after working out in the morning something to be concerned about? With continued progress – should high levels get better over time?
Christel Oerum
I personally wouldn’t be too concerned if it doesn’t stay up for too long. However, since we are all different and you might have other health considerations to take into consideration, I suggest you discuss it with your medical team.
Sandra
I always exercise to lower blood sugar however for some time sugar spikes after exercisr I tried different type of exercise but it always spikes to over 200. Confused not on insulin.
Christel Oerum
There can be many reasons for that. Most often you can try eating a small protein snack before your workout. Second measure your blood sugar 30-45 min after your workout, it might have come down, and then there’s no worry. If not try adding 20-min walking after your workout
John
Hey Cristel, just read your views on blood sugar levels rising after exercise. That was driving me nuts for a long time. I’ve had diabetes for about 20 some years (got it when I was around 30). I’ve always been pretty active but after I play racquetball it will shoot up to the high 200s or more! Should I take a dose of insulin before I play? It also affects my morning sugars the next day which will drop to below 50 (I feel like I’m on a weird rollercoaster quite a bit!)
Christel Oerum
If you consistently see an increase you could try taking the correction before or mid-game. But be careful, and increase your blood sugar measurements when you experiment.
We’re of course all different, but here’s what I do. I have a good feel for which types of exercise will make my blood sugar climb immediately and which will make them climb after (thanks to CGM) so I’ll dose prior or during depending on the type of exercise.
A drop in blood sugars overnight/morning after exercise is also quite common and the guidelines (Lancet 2017) say to consider reducing your basal the night after hard exercise or consume more carbs
Kate JOSEPH
Thank you for your insight into exercised T1 DM. I am currently exercising to loose weight and was finding it really frustrating that I’d be running hi after a hiit. You article have given me such joy, seriously, thank you. I’m gonna try different approaches. I shall now research you more and follow you. Its do great to have some decent T1 DM advice. Big hugs. Kate Jo. Been T1 for 36 yrs!!! Xx
Christel Oerum
You just put a huge smile on my face. So glad this is helpful
Ianna
Hello ,
I just started reading your blog . I’m so excited and full of joy as I read every sentence of your articles . Thank you for helping the Diabetic community . I’m a type 1 for many years . I struggle tons with hypo/ hyper glucose levels before during and after exercising – it all makes sense now as I absorb your knowledge . I’m took myself off from the Medtronic pump . Now , Ill be a pen user for a bit . My question to you is : i recently signed up with orange theory – i absolutely love it . So where should I categorize orange theory – steady cardio or interval training ? Ive checked my self before class sometimes glucose is at 150 ( i still eat a sugar tablet – maybe I’m fearfull to face a low blood sugar ) after 1 hours I check again and I’m at 100 . But 1h after I check again ( no food ) and I’m at 160 . It gets very confusing .
Christel Oerum
I’m so happy to hear that the website is helping you!
Orange Theory, and other mixed classes like it, is tricky since it’s a combination of aerobic and anaerobic. In some classes, you’ll know if it starts with cardio and then you do weights or if it’s all just one big mix.
If I’m in a class that do cardio first and then weights, I’d do a try to limit how much insulin I’d take the 4 hours before class and do a correction right before class start (that should start working after 30-min so fits with when I’d do weights). I use the same strategy for mixed classes.
If the cardio is the second part of the class I’d try and go in with some level of IOB but not do any doses the 2 hours before. But that’s what works for me. Start by getting enough data points to see if you always drop and then go up, and then adjust from there
Ianna
Thank you for your prompt response !
Guru
Hey Christel,
I just started reading your blog and find many of your answers quite interesting. So if interval training spikes blood sugar then what is the use of doing interval training? I am working out the past three months to lose weight as I am very obese, but when I check my blood glucose after workout it keeps spiking by at least 40 points (I usually don’t eat anything before workout). I am working very hard in hopes of losing weight and becoming super fit so that my blood glucose can be under control. In the long run, will this glucose imbalance change or should I change my habits?
Am also having a zero carb – zero sugar protein shake (half scoop) after workout, will that also have an impact on blood glucose? Looking forward to your response.
Christel Oerum
Although your blood sugar might rise during your workout your insulin sensitivity should be improved over time so it’s definitely a workout worth doing. You could try eating a small meal before to help manage your blood sugar during your workout. For some that help.
And yes, pretty much anything that ultimately converts to energy (glucose) will have some sort of impact on your blood sugar. That doesn’t mean that you should stop eating, but something to be mindful of
Ervin Epps
I appreciate your post about resistant exercise & cardio exercise. Ive been a type-1 diabetic since 2001. Once I was diagnosed I became reluctant to continue exercising because of hypoglycemic episodes. Thanks for the info. It’s motivating to know that I can return to exercising, especially given the knowledge from another diabetic who understands the stresses that we encounter daily from non-diabetics & diabetics alike. Thanks again for the knowledge. Marine veteran motivated to rediscover my physical abilities that I once doubt could happen.