A Ketogenic or Very-Low-Carb Diet for Type 1 Diabetes

By Franziska Spritzler, RD, CDE

Have you ever wondered if changing your diet could lead to better control of your type 1 diabetes and provide other benefits? For many people, a ketogenic (keto) diet, which is very low in carbohydrates, can be a helpful strategy.

In this article, we explore what type 1 diabetes is, the scientific evidence supporting a very low-carbohydrate approach, concerns about ketogenic diets, and practical tips for following a ketogenic diet safely and sustainably as a person living with type 1 diabetes.

What is Type 1 Diabetes?

Type 1 diabetes is an autoimmune condition that destroys the insulin-producing beta cells of the pancreas. Insulin is a hormone that helps regulate blood glucose (blood sugar) levels. Without insulin, blood glucose will rise to dangerous levels that cause severe illness within hours and death within a few days. Because they can no longer produce their own insulin, people with type 1 diabetes need to inject insulin –– via a wearable pump or as multiple daily injections –– to control their blood glucose levels.

Risk Factors for Type 1 Diabetes

Type 1 diabetes is believed to be triggered by a virus or other stressor that prompts the immune system to attack the pancreatic beta cells. However, genetic and environmental factors play a large role in developing this disease. Some of the risk factors include:

• Family history: A person with a parent or sibling with type 1 diabetes has a 3- to 15-fold increased risk for developing it.
• Genetics: Certain genes, particularly those that related to Human Leukocyte Antigens (HLA), are known to significantly increase the risk of type 1 diabetes.
• History of autoimmune disease: People with an existing autoimmune disease –– such as celiac disease, Hashimoto’s thyroiditis, or rheumatoid arthritis –– are more likely to develop type 1 diabetes.

People with Type 1 Diabetes Often Have Suboptimal Glycemic Control

Elevated blood glucose levels have been shown to significantly increase the risk for complications like chronic kidney disease, retinopathy (eye damage), neuropathy (nerve damage), and cardiovascular disease. Thus, achieving and maintaining good glycemic control is crucial for living a long, healthy life.

Long-term diabetes control is assessed by a blood test known as the Hemoglobin A1c (HbA1c, or simply A1c), which reflects blood glucose levels over a period of approximately three months.

The American Diabetes Association (ADA) sets a target A1c level of <7% for nearly everyone with diabetes (type 1 or type 2).

Unfortunately, many individuals with type 1 diabetes don’t achieve this target. A 2015 analysis of data from over 6,000 participants with type 1 diabetes revealed average A1c levels of 7.5% to 9% among children, adolescents, and adults in the US. A much larger 2021 analysis of data from over 500,000 people in 22 countries reported similar results among different ages and genders.

An A1c of 7% reflects an average blood glucose level of 154 mg/dL (8.6 mmol/L). By contrast, an A1c of 5.6% –– the uppermost end of the range considered normal in people without diabetes –– reflects an average blood glucose level of 114 mg/dL (6.3 mmol/L).

Some people have asked, if the goal of blood glucose management is to avoid diabetes-related complications, why is the A1c target set at <7% for people with diabetes rather than ≤5.6%? It’s a valid question.

High Insulin Doses Can Be Problematic

Although achieving good glycemic control is key to avoiding diabetes complications, injecting large doses of insulin to control blood glucose can further increase health risks in people with type 1 diabetes.

Here’s why. After you eat a meal, your digestive tract breaks down the carbohydrates (carbs) from that meal into glucose, which is absorbed into the bloodstream. Eating a high-carb diet requires high amounts of insulin to move glucose out of the bloodstream and into the body’s cells. Insulin is crucial to sustain life in people with type 1 diabetes, but it is also an anabolic hormone that can drive weight gain in large amounts.

Although type 1 diabetes is typically viewed as a disease that occurs in people of normal or low weight, obesity is becoming more common in this population. The term “double diabetes” is used to classify people with type 1 diabetes who have insulin resistance and obesity, which places them at even greater risk for complications like cardiovascular disease.

In addition to negatively impacting metabolic health, large amounts of insulin may increase the risk for hypoglycemia or hyperglycemia due to a mismatch between the carbohydrates that are consumed and the insulin that is injected. This can occur as a result of overestimating or underestimating one or more of the following:

• the amount of carbohydrates consumed

• how quickly the food will be digested

• how much of the insulin will be absorbed and how quickly it will begin working

A Ketogenic or Very-Low-Carbohydrate Approach for Type 1 Diabetes

Ketogenic and very-low-carb diets are sometimes referred to as therapeutic carbohydrate restriction or therapeutic carbohydrate reduction.

A ketogenic diet is very low in carbohydrates, moderate in protein, and high in fat. A very low-carbohydrate diet is typically higher in protein and more moderate in fat. However, the terms are often used interchangeably to describe diets that provide less than 50 grams of total carbs per day or less than 30 grams of net carbs* per day. Either approach can help people with type 1 diabetes control their blood glucose levels.

Unlike those with type 2 diabetes, who can often discontinue insulin and diabetes medications by switching to a very low-carb diet, individuals with type 1 diabetes will need to take some insulin every day for the rest of their lives regardless of what they eat. This is because small amounts of basal insulin are needed to sustain life during non-eating periods. However, they can reduce their mealtime (bolus) insulin doses and achieve better blood glucose control by minimizing their carb intake.

Dr. Richard K. Bernstein is a physician who has been living with type 1 diabetes for more than 75 years and following a very low-carb diet for more than 50 years. He attributes his normal blood glucose levels, and those of his patients, to his concept of “The Law of Small Numbers”: Smaller inputs of carbohydrates require smaller doses of insulin, resulting in more predictable and stable blood glucose levels. At 90 years old, Dr. Bernstein is in excellent health and still practices medicine.

As reported in online forums and success stories, many people with type 1 diabetes who follow Dr. Bernstein’s protocol or other very-low-carb/ketogenic lifestyles report dramatic improvements in their blood glucose control and quality of life.

Scientific evidence also supports these approaches. There is admittedly far less research on therapeutic carbohydrate reduction for type 1 diabetes compared to type 2 diabetes. This is mainly because more than 90% of all diabetes is the type 2 form, so fewer studies have been conducted in people with type 1 diabetes.

However, research in this area is growing. To date, studies have shown that ketogenic and very low-carb diets can provide several benefits in people with type 1 diabetes.

Note: Although some of these studies use the term “ketogenic” and others use “very low carbohydrate,” they all describe approaches providing no more than 50 grams of total carbs or 30 grams of net carbs per day.

• A 2018 survey of more than 300 adults with type 1 diabetes who eat a very low-carb diet reported that participants achieved exceptional A1c (mean 5.67%) and blood glucose (mean 106 mg/dL or 5.9 mmol/L) levels. They also reported low rates of adverse events such as hypoglycemia.

• A 2022 retrospective study of 33 patients with type 1 diabetes who ate a very-low-carbohydrate diet for 12 months reported better glycemic control, a four-fold increase in patients who achieved A1c levels below 7%, lower daily insulin requirements, and fewer episodes of level 2 hypoglycemia (blood glucose less than 54 mg/dL or 3 mmol/L).

• A 2023 case study reported that a young man with type 1 diabetes achieved normal blood glucose levels (A1c of 5.1%) and reduced his insulin requirements by nearly 70% by following a ketogenic diet.

• A 2023 review concluded that, although published research is sparse and more studies are needed, ketogenic diets are a promising approach for type 1 diabetes due to their anti-inflammatory properties, ability to stabilize blood glucose levels, and potential effects on pancreatic function.

According to clinicaltrials.gov, several researchers are currently recruiting participants for trials exploring ketogenic and low-carbohydrate diets in type 1 diabetes.

Eating a very low-carbohydrate diet may also help prolong the “honeymoon phase” in type 1 diabetes. This is the term that is often used to describe the brief remission period that occurs in some individuals shortly after diagnosis, when beta-cell function temporarily improves due to lower blood glucose levels from exogenous insulin therapy and improved immune response. A ketogenic or very low-carb diet can reduce the glycemic load and decrease stress on the remaining beta cells, helping preserve their function for a longer time. Indeed, several case reports have shown prolonged diabetes remission (between one and four years) in newly diagnosed people with type 1 diabetes who followed a very low-carb or ketogenic diet.

*Net carbs are the total grams of carbs in a food minus the grams of fiber it contains.

Concerns About Ketogenic Diets for Type 1 Diabetes

Although therapeutic carbohydrate restriction has been shown to provide benefits for people with type 1 diabetes, critics have questioned whether it is healthy and safe. Precautions should be taken to ensure the safety and sustainability of individuals with type 1 diabetes who opt for a ketogenic or very-low-carb diet. But in most cases, concerns that these approaches will jeopardize health are misguided.

Here are a few of the most common concerns:

• Risk of diabetic ketoacidosis (DKA): Concerns have been raised that a ketogenic diet could increase the risk of DKA, a dangerous condition where blood ketone and blood glucose levels rise to extremely high levels due to a lack of insulin. However, nutritional ketosis is very different from ketoacidosis. Recent research suggests that people with type 1 diabetes who follow a ketogenic or very low-carb diet and take appropriate insulin doses maintain ketone levels well within levels of nutritional ketosis (0.5 to 3.0 mmol/L). Monitoring blood glucose and ketone levels regularly can ensure that these values remain in the safe range and alert you to take action early if you notice your levels trending in the wrong direction.

• Risk of hypoglycemia: Eating very few carbohydrates does not cause hypoglycemia; having too much insulin in your system does. It is crucial to lower insulin doses when beginning a ketogenic or very low-carb diet, along with checking blood glucose levels more frequently. Working with your doctor or diabetes educator to adjust your insulin regimen can minimize your risk of hypoglycemia.

• Changes in cholesterol levels: Ketogenic diets are frequently criticized because they are believed to raise LDL cholesterol levels and increase cardiovascular disease risk. Although this topic hasn’t been studied much in people with type 1 diabetes, studies show that very-low-carb diets typically lead to favorable changes in lipid profiles in people with type 2 diabetes, such as higher HDL cholesterol, lower triglycerides and larger LDL particle sizes, without significantly increasing LDL cholesterol.