The ketogenic diet (“keto”) has been around for a long time. It’s popular. It’s controversial. Some love it. Some hate it. Some even say it can help your blood sugar levels stay in better control.

After thoroughly reviewing the scientific literature and trying the ketogenic diet myself for over six months, I am ready to explore everything you’ve been hearing and let you decide for yourself what you think about the diet that has taken the world and diabetes community by storm.

This guide is relevant for people with any type of diabetes. I will mainly talk about insulin when I discuss how a keto diet affects blood sugar, but some studies also show a possible reduction in certain type 2 medications. 

Disclaimer: Please always consult with your medical team before you start a new diet, adjust your medication, or change your diabetes management routine.

The Ketogenic Diet and Diabetes

Key Points:

  • The ketogenic diet is a low-carb, high-fat diet that forces the body to burn fats rather than carbohydrates for fuel. Originally used as a diabetes-management method before insulin was discovered, it involves consuming roughly 75 to 85 percent fat, 10 to 20 percent protein, and 5 to 10 percent carbs daily.
  • The diet can lead to better blood sugar management due to reduced carbohydrate intake and improved insulin sensitivity. However, experiences vary significantly from one person to the next, and it’s not universally effective for everyone with diabetes.
  • While the diet may be effective for some for short-term weight loss due to reduced hunger and increased feelings of fullness from fats and proteins, success for this purpose still relies on maintaining a calorie deficit, among other factors. Long-term safety and effectiveness compared to other diets need more research.
  • The diet’s suitability varies from person to person. Some may find it beneficial for managing blood sugar and weight, while others might experience increased insulin resistance or difficulty sticking to the diet.

Table of Contents

What is a ketogenic diet?

In the 1920s, keto was the original “diabetes diet” prescribed to people with type 1 diabetes before the discovery of insulin. This would prolong their lives, as the diet is less likely to raise blood sugar levels due to its low carbohydrate content. (Carbohydrate is the main nutrient that raises blood sugar levels.)

The ketogenic diet is a low-carb diet where you get only about 5 to 10 percent of your daily caloric intake from carbohydrates. By restricting your carbohydrate intake so severely, you force your body to get most of its energy from fat. A byproduct of this fat-burning is the production of natural ketones in the body, hence the name of the diet.

Burning fat to produce ketones supplies the body with an alternative form of energy rather than quickly accessible energy from carbs (glucose) and is what defines the ketogenic diet. The two main reasons why a person with diabetes would follow a keto diet are:

  1. To reduce insulin need and avoid blood sugar fluctuations
  2. To aid weight management (weight loss)

In the rest of this guide, I will review the pros and cons of a keto diet and try to answer the most significant question: “Is a keto diet good for people with diabetes?”

Some sample foods recommended for this diet include:

  • Meats (e.g., beef, pork, lamb, poultry, and game meats; preferably grass-fed and organic, if possible)
  • Fatty fish (e.g., salmon, mackerel, sardines, trout, and other fish rich in omega-3 fatty acids)
  • Eggs (preferably free-range or omega-3-enriched eggs)
  • High-fat dairy (e.g., butter, cream, and certain cheeses)
  • Nuts and seeds (e.g., almonds, walnuts, flaxseeds, pumpkin seeds, chia seeds)
  • Healthy oils (primarily extra-virgin olive oil, coconut oil, and avocado oil)
  • Avocados (whole avocados or freshly made guacamole)
  • Low-carb vegetables (e.g., green veggies, tomatoes, onions, peppers)
  • Condiments (e.g., vinegar, mustard, hot sauce, garlic, herbs, and spices)
  • Beverages (e.g., water, unsweetened coffee and tea)

A dietitian can help you figure out the best combination of foods to eat, taking into consideration your lifestyle and overall health goals.

How much fat, protein, and carbs to eat on a keto diet

To follow a keto diet, you’re looking at approximately this split in daily calorie intake:

  • 75 to 85 percent fat
  • 10 to 20 percent protein
  • 5 to 10 percent carbohydrate, or approximately 20 to 50 grams per day

As an example, if we converted this to grams for a person on a 2,000-calorie diet, this equals:

  • 167 to 189 grams of fat
  • 50 to 100 grams of protein
  • 25 to 50 grams of carbohydrates

NOTE: I am NOT saying that you should eat a 2,000-calorie diet. This is just an example! Please read this post to learn how to calculate your daily calorie needs.

When following a ketogenic diet, it’s crucial to keep your protein intake in check. In the absence of carbohydrates, the body can use protein to create glucose through a process called gluconeogenesis. 

This can kick you out of ketosis. Therefore, it is recommended to limit your protein intake to less than 1 gram of protein per pound of body weight to maintain ketosis (unless you regularly engage in heavy weight lifting). 

I will be spending the rest of the article talking from the 20 to 50 grams of carbs and moderate protein (about 20 percent) perspective. 

How does a keto diet affect blood sugar?

The premise of the ketogenic diet and diabetes is straightforward: fewer carbs require less insulin and should result in fewer blood sugar spikes. Fewer blood sugar spikes should lead to increased time in range and better A1c values (a measure of glucose control over the previous 2 to 3 months).

In addition, several studies have shown that the keto diet can improve insulin sensitivity, further reducing the need for insulin and making blood sugar control easier.

If (and that is a big if) you can adhere to it, keto can be a very effective way to manage your blood sugars. The blood sugar swings will truly start to dissipate, trendlines on CGMs will flatten, and your A1c will quite possibly drop. I had the best A1c of my life while doing keto.

On the flip side, “hypos” (low blood sugar) can be an issue, especially early on after adopting the keto diet. If you treat the hypos too aggressively, they could knock you out of ketosis. 

During my first three weeks on keto, my CGM trend line hugged a blood sugar of around 80. It was glorious, but I had to reduce insulin substantially through trial and error and felt like I was low every five seconds.

When I would overtreat a low, I would sometimes push my carbohydrate amount over the keto threshold and end up OUT of ketosis. While that is not the worst thing in the world, the goal is to remain in ketosis as much as possible.

The keto diet is a popular low-carb diet for people with diabetes, and many people swear by its effectiveness in blood sugar management. 

However, there are also people (including Christel Oerum, the owner of Diabetes Strong) who experience an opposite reaction when following the keto diet. Instead of increased insulin sensitivity, they experience a drastic increase in their insulin resistance. As a result, they need large amounts of insulin, even for a very small amount of carbs.

While this increase in insulin resistance on the keto diet is in contrast to most research, there has been an animal study that supports this phenomenon. More research is needed, but there is enough anecdotal evidence to suggest that not everyone reacts the same to a keto diet, and it may be unsuitable for some people.

Verdict: The keto diet can be effective for blood sugar management, but there is significant variation between individuals. It does not work for everyone, but with the OK from your healthcare team, it could be worth trying to see how it works for you.

Is a keto diet effective for weight loss?

Given that the whole idea of the keto diet is to burn fat instead of carbs for energy, it seems logical that the keto diet should be effective for weight loss. 

While this is also often the case, it’s important to remember that individual results may vary, and there are other factors that can impact weight loss, such as overall calorie intake, diet quality, hormonal and physiological responses, metabolism, and exercise levels.

Therefore, following a well-balanced keto diet that meets your individual needs and goals is key for improved weight loss outcomes.

To learn more about how to manage body weight with diabetes, read How to Lose Weight With Diabetes and follow the steps in the post How to Find Your Daily Calorie Need to calculate your optimal daily calorie intake.

The theory behind using a keto diet for weight loss

Proponents of using a keto diet for weight loss argue that eating carbs drives up insulin production, which increases hunger and causes the body to hold on to fat and suppress calorie burn. When you replace carbs with fat, you decrease the need for insulin, subdue hunger, boost calorie burn, and melt away fat.

Many people also report fat as very satiating, making them feel full. The same goes for protein. When you feel full, you eat fewer calories and have fewer cravings. When you are at a healthy caloric deficit, you are primed to lose unwanted pounds.

What the science says…

Research has consistently shown that there is no significant difference in weight loss between a very low-carb or low-carb diet and comparison diets after 6 to 12 months.

However, long-term effects (beyond one year) are not often studied due to budgetary constraints and other factors, so interpret results as you wish.

Verdict: A keto diet is not inherently better for weight loss than other diets. However, it be very effective for weight loss (at least short-term) if it:

  • Helps you manage your blood sugar better than other diets
  • Is easier for you to follow than other diets
  • Works for your general lifestyle

As with most other diets, the main criteria for success is whether or not it is sustainable for the long term. If you like the keto lifestyle, the diet can work great. If you hate it, it probably won’t work for you.

A quick note on keto and water retention

You often hear people who start a keto diet exclaim, “I’ve been keto for a week, and I’ve already lost 6 pounds! I love it!”

While this can be a great motivator to stick to the diet, most of that initial weight loss consists of water due to less glycogen storage (glycogen is the storage form of glucose).

Why? The old saying goes, “Wherever glycogen goes, water follows.”

Because you eat fewer carbs, you will have fewer glycogen stores. Less glycogen means less water is retained. Less water is retained, and, you guessed it: the scale goes down. There is nothing wrong with that — just don’t mistake lost water weight for fat loss.

Keto diet and exercise

Starting on a ketogenic diet can influence your exercise performance in multiple ways. During the “adaptation period” (which I will get back to later), you will most likely see a decrease in energy and athletic performance across the board while your body adjusts to the new diet. 

When your body has adapted to the ketogenic diet, you will most likely experience that cardio returns to its previous level of difficulty, but strength training may or may not be harder.

Do not expect major improvements in cardio

Despite having access to stored fat as fuel, individuals may not experience significant performance improvements in cardio fitness by following a ketogenic diet. 

In fact, for recreational athletes (regular exercisers), a ketogenic diet usually doesn’t significantly affect their cardio performance after adaptation.  

According to numerous studies, low-carb and ketogenic diets also do not improve exercise performance in trained athletes and may actually decrease performance, particularly in females.

Strength may suffer

Emerging research suggests that while the ketogenic diet may be effective for short-term fat loss, its impact on muscle growth and strength is questionable, and it might not be the ideal dietary approach for those seeking to increase muscle mass and athletic power. 

The long-term implications and safety of the ketogenic diet, particularly concerning body composition and strength outcomes, warrant further investigation.

Personally, all of my lifts dropped 40 to 50 pounds for the first four to six weeks after I switched to a keto diet. Weights that I used to toss around with ease became tougher to move until I was fully adapted.

It may not be impossible to improve strength while on a keto diet, but it can make the process substantially more challenging.

How difficult is a keto diet to follow?

This is the most important, but also most subjective, question about any diet. If you don’t feel physically and mentally well on a diet, it won’t lead to long-term results because you won’t adhere to it.

The keto diet is probably one of the most polarizing diets when it comes to people’s opinions on how easy it is to follow. Some people love it almost from day one, while others experience major food cravings and even physical discomfort.

This is what my experience with a keto diet was like. Yours may be different:

Keto adaptation is ROUGH

It takes a while to become what is known as “keto-adapted,” the body’s process of adjusting to a ketogenic diet. It  is your body’s way of saying “hey, I got this, I’m ready to mainly burn fat!”

The length of the adaptation period depends on individual differences such as sex, age, and level of physical activity. Research indicates it may take weeks or months for your body’s organs to fully adapt to utilizing ketones. 

Cardio exercise might help to speed up this keto-adaptation process, though more research is needed.

Keto expert Ariel Warren, RDN, CD, CDCES, suggests that keto-adaptation may also depend on how many carbohydrates you are used to eating. For example, if you’re transitioning from a higher-carbohydrate diet, she says it may take longer to adapt. 

During the first few weeks of following the keto diet, your body is rebooting what it has known for pretty much your entire life. Your brain is used to running on glucose and suddenly, it doesn’t have it. Now, it craves it. You’re in glucose withdrawal.

Some describe this phenomenon as the “keto flu,” where you basically feel the opposite of everything promised — sick, fatigued, nauseous, mentally cloudy, etc. — it’s not very pleasant.

Oh, and I should probably also mention that low carb often means low fiber, meaning digestive issues like bloating, constipation, or diarrhea can be an issue. It’s often recommended to limit sodium and to include more high-fiber, low-carb foods like avocados, raspberries, and spinach to help support your digestion-elimination process.

Talk to your healthcare provider if you continue to experience constipation and other digestive problems on the keto diet. 

Is a keto diet safe for people with diabetes?

There haven’t been a lot of studies done on the long-term safety and effectiveness of following a keto diet, especially for people with diabetes, and this is an area of ongoing research. Thus far, it appears to be safe and effective for some people with diabetes in the short term (for up to six to 12 months).

One of the main risks when following a keto diet (or any other diet that restricts food choice and calorie intake) is becoming deficient in essential vitamins and minerals due to a significant reduction in diet quality (eating far fewer healthy, plant-based foods like fruits, vegetables, whole grains, and legumes because they often contain moderate amounts of carbohydrates). 

Often overlooked, another risk of restrictive dieting is related to mental health. Any restrictive diet can potentially lead to an unhealthy relationship with food, and, in some cases, may contribute to disordered eating patterns or eating disorders.

If you find yourself constantly thinking about food, avoiding social situations where food is involved, or struggling with a negative body image, please seek the help of a mental health professional or a registered dietitian specializing in this area

NOTE: It’s important to stress that this risk isn’t related specifically to a keto diet but restrictive dieting in general!

Additional potential risks of the keto diet can include:

  • Initial side effects such as fatigue, headache, nausea, and constipation
  • Elevated risks of hypoglycemia (low blood sugar) for those on insulin or drugs that promote the release of insulin 
  • Ketoacidosis, dehydration, and various forms of electrolyte imbalance
  • Possible negative impacts on bone health, such as reductions in bone mineral density
  • Negative effects on cholesterol levels, particularly increasing LDL (“bad”) cholesterol
  • Kidney stones, increased risk of kidney disease, or worsening of kidney disease
  • Potential development of serious heart conditions and eye nerve damage

Keto diet and ketoacidosis

Diabetic ketoacidosis can occur in individuals with diabetes when there is an inappropriately high level of ketones in the body. 

This usually happens due to a lack of insulin and is more common in people with type 1 diabetes. However, it can also occur in people with type 2 diabetes who require insulin and miss an insulin shot, have a clogged insulin pump, or use an incorrect insulin dose. 

Without insulin, sugar cannot be used by your cells for energy, so the liver breaks down fat for fuel instead, thereby producing ketones. Ketones can then build up in the blood, turning the blood acidic, hence acidosis.

Other causes of diabetic ketoacidosis may be the presence of illness, infection, or severe dehydration. 

Ketogenic diets are being linked more frequently to ketoacidosis in people with and without diabetes. 

To monitor for ketoacidosis, you can measure the ketone level in your body with a urine test. You can buy ketone test kits over the counter at most drug stores and pharmacies.

Urine ketone levels

You can also get test kits that use a drop of blood instead of urine. They use a different measuring scale, so please always read the packaging carefully before taking any ketone test.

Keto diet and pregnancy

A ketogenic diet is not recommended for women who are pregnant, breastfeeding, or have gestational diabetes. There haven’t been enough studies to show that it’s safe, and it may have harmful effects on the baby during pregnancy.

The diet is also advised against for those with a variety of other health conditions, including pancreatitis, liver failure, and more. Visit the National Library of Medicine for a more comprehensive list.

Final thoughts: Is a keto diet good for people with diabetes?

A keto diet may be an effective short-term strategy for people with diabetes. Some of the potential benefits include:

  • Better blood sugar management
  • Initial weight loss 
  • A feeling of fullness (fewer cravings)

However, individual differences can greatly affect the body’s reaction to the keto diet. Some people may experience weight gain or worsening blood sugar levels. 

Furthermore, the keto diet may be less safe for those with type 1 diabetes due to the increased risk of ketoacidosis. 

If your doctor approves, try following a keto diet for a while (at least two to three weeks, as the beginning is always hard) to see how it works for you.

If you feel that a keto diet isn’t working for you after trying it, definitely don’t feel compelled to follow it just because some people with diabetes recommend it. 

There are many great alternatives, such as the Mediterranean (MED), Dietary Approaches to Stop Hypertension (DASH), or MIND (combined MED and DASH) diets. 

I tried following a keto diet for a while but eventually went back to a more traditional medium-carb diet. It simply works better for me!

I hope this guide has given you a full view of the ketogenic diet and diabetes. At the end of the day, it’s up to you and your healthcare team to decide if you want to try it and see if it has any beneficial effects on your blood sugars, body composition, or just how you feel. If you go for it, a good place to start is with this ketogenic meal plan. Good luck!