Is the Keto Diet Safe for People With Diabetes?

The ketogenic (keto) diet has become a popular trend among people trying to lose weight. And because the diet significantly restricts carbohydrates (carbs), it can have a notable impact on the way your body processes sugar and fat. If you have diabetes, you may be wondering if this diet is right for you. But the answer to this question is more complex than it seems. And the keto diet may not be the best long-term strategy to improve diabetes. We’ll review the research and what it tells us about the positive and negative ways this particular diet can affect people with diabetes. 

What is the keto diet? 

The keto diet is a diet low in carbohydrates that’s intended to put your body into a state of “ketosis.” Ketosis is a sort of “starvation mode,” which triggers your body to burn fat — instead of sugar — for fuel. So when your body is in ketosis, fat stores are depleted and blood sugar levels remain low. 

People who follow a keto diet usually restrict themselves to a total of 50 grams of carbs daily. To compare, the average well-balanced diabetic diet usually contains 200 to 225 grams of carbs. 

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Does the keto diet help diabetes? 

There’s evidence to suggest that carbohydrate restriction can improve blood sugar control in people with Type 2 diabetes. But it’s less clear whether a more restrictive, ketogenic approach is helpful or sustainable over the long term.

Research suggests that a low-carbohydrate diet improves blood sugar and hemoglobin A1C (HbA1C or A1C)  — a blood test that indicates your blood sugar control over the last 3 months. For example, one study found that a low-carb diet was more effective than a low-fat diet at controlling blood sugar and lowering A1C. And some of the study participants were also able to decrease their insulin dose. Another study showed similar results and observed that, in comparison to a low-calorie diet alone, a low-carb diet more effectively controlled blood sugar and lowered the need for diabetes medications. 

But it’s important to note that these studies looked at low-carb diets, not ketogenic diets specifically. And keto diets are notoriously hard to adhere to over the long term. In fact, two large-scale analyses compared a more restrictive (ketogenic) diet to a more moderate low-carbohydrate diet in people with Type 2 diabetes. Both analyses found that a greater carb restriction led to better blood sugar control over the short term (3 months). But these results were not sustained over the long term (12 months).  

So while keto diets may initially lead to weight loss and improvement in blood sugars, it’s unclear if there is any long-term benefit.

Can the keto diet reverse diabetes?

There’s no solid evidence to suggest that a keto diet can reverse diabetes.

A recent meta-analysis of multiple studies found that after 6 months, a keto diet normalized A1C levels for people who remained on their diabetes medications. But this reversal effect wasn’t seen in people who discontinued their medications. So it’s hard to say if this was a true reversal of diabetes by the keto diet alone. What’s more, the reversal effect was not maintained after 12 months for either group.  

Is it safe for someone with diabetes to do the keto diet? 

Switching to a keto diet can cause symptoms for someone who isn’t used to eating this type of diet. These symptoms include:

• Increased urination

• Dehydration

• Constipation

• Low blood sugar — or hypoglycemia — in people taking certain medications for their diabetes

If you’re taking medication for your diabetes, you should talk with your provider before starting a keto diet. They can help you make any medication adjustments to avoid dangerous drops in your blood sugar. 

People who may be at risk of serious side effects from ketosis should approach this diet with caution. That’s because a ketotic state can put extra strain on the body’s systems. People who may be especially sensitive to a keto diet include those who:

• Are pregnant

• Have kidney disease

• Have Type 1 diabetes

If those situations apply to you, talk to your provider before attempting to transition to the ketogenic diet to make sure it’s safe.

Why might the keto diet be bad for someone with diabetes?

In addition to unpredictable drops in blood sugar, there are concerns that the keto diet may not be best for our overall health in the long term. More research is needed to look at the long-term consequences of a keto diet over years or even decades. And experts need to look at the impact on other health conditions that are associated with diabetes — like heart disease.

Some studies show improvement in markers of heart health — like cholesterol levels — with the keto diet. But there are also studies that show the opposite effect. One meta-analysis showed that keto diets may increase LDL cholesterol over time, which is a risk factor for heart disease. When someone lowers their carb intake, this translates to increased fat and protein intake to maintain the same calories in their diet. And in general, high-fat diets aren’t recommended for heart health.

Another thing to consider is that a high-fat diet — like the keto diet — may negatively affect the way our body processes carbs. One study from 1927 compared people who ate a high-fat diet for only 2 days to those who ate a regular diet. And they found that after the 2-day period, those on a high-fat diet had significantly higher blood sugar spikes when they ate carbs. Additional studies have also linked diets high in fat to abnormal glucose processing in the body. 

Overall, it’s important to consider the long-term effects of the keto diet. Blood sugars can definitely improve when someone significantly reduces the amount of carbs they eat. But high blood sugar is a symptom of diabetes. The underlying cause of diabetes is abnormal processing of carbs by the body. And we still need more research to understand if the keto diet helps or hurts this process. 

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Written by:

Joanna Jan, MD

Joanna Jan, MD, is board-certified in internal medicine and licensed to practice medicine in the state of Pennsylvania. In 2017, she received her board certification from the American Board of Internal Medicine.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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