Type 1 diabetes – how to control your blood sugar with fewer carbs
Type 1 diabetes – previously called “juvenile-onset diabetes” – results when the body is no longer able to produce the hormone insulin. Insulin keeps blood glucose (sugar) levels under control by transferring glucose from the blood vessels into the body’s cells, where it is used as energy. Type 1 diabetes is treated with insulin injections.
The more carbohydrates you eat, the more insulin will need to be injected. Thus, perhaps not surprisingly, studies and experience have shown that low-carb diets can be beneficial for people with type 1 diabetes.1
The main benefits are preventing blood glucose spikes after meals and reducing the risk of low glucose levels (hypoglycemia). This makes it easier to maintain stable and near-normal blood glucose levels.
However, there are special considerations that people with type 1 diabetes need to be aware of when adopting a low carb diet. So here is our guide to low-carb diets in type 1 diabetes.
This guide is written for adults with type 1 diabetes.
For other controversies related to low carb, see our full guide
What is type 1 diabetes, and how does it differ from type 2?
Type 1 diabetes is an autoimmune disease that destroys the insulin-producing cells of the pancreas, known as beta cells. This ultimately leads to a complete lack of insulin.
By contrast, in type 2 diabetes the beta cells usually produce insulin, but the body cannot use it properly as its cells, especially the muscle and liver cells – are resistant to it. This prompts the pancreas to produce more insulin, leading to high insulin levels known as hyperinsulinemia.
In both types of diabetes, glucose accumulates in the bloodstream, as it cannot enter the body’s cells, due to the absence of insulin (type 1) or resistance to it (type 2). Without treatment, blood glucose levels remain elevated and over time causes damage to many parts of the body.
Unlike type 2 diabetes, which can often be managed by diet and other lifestyle modifications, people with type 1 diabetes need to inject insulin every day, to cover their meals. Insulin is also essential, even when not eating.
This is because the liver continually releases glucose into the bloodstream when we are not eating, in order to ensure there is enough glucose available for the body’s needs. This release from the liver is controlled by insulin, and without insulin, there would be a constant leak of glucose from the liver into the bloodstream, in addition to the glucose entering the bloodstream from the gut when we eat.
Most people with type 1 diabetes are treated with a basal-bolus insulin regimen. This requires injection of long-acting insulin once or twice daily that mimics the effect of basal insulin to keep the release of glucose from the liver under control. This insulin is required every day, usually at the same dose, regardless of the amount of food eaten.
It also requires injection of fast-acting ’bolus’ insulin just before each meal. Some people take the same dose for each meal, however, ideally, the dose should vary according to the amount of carbohydrate in the meal, using an insulin to carbohydrate ratio, for example, 1 unit for every 10 grams of carbohydrate in the meal.
Some people with type 1 diabetes are treated with two injections a day of mixed (long and fast-acting) insulin. This does not allow the flexibility of a basal-bolus regimen and usually requires a more standardized meal pattern to maintain stable glucose levels.
Type 1 diabetes is sometimes referred to as juvenile diabetes because it is typically diagnosed in children and young adults. However, it can develop at any age, including in the elderly. The oldest person reported to have been diagnosed with type 1 diabetes was a 94-year-old lady.2
In older adults, autoimmune diabetes often involves a more gradual destruction of beta cells. This slow, progressive form of diabetes is known as latent autoimmune diabetes in adults (LADA). People with LADA may still produce some insulin, especially when first diagnosed. However, they will eventually require insulin injections in order to control their blood glucose, just like people with type 1 diabetes.3
Learn more about type 2 diabetes
For more on type 2 diabetes, check out this guide: Guide on type 2 diabetes and the videos below.
What are the risks of type 1 diabetes?
People with type 1 diabetes are at increased risk for a number of health issues, including heart disease, kidney disease, loss of vision, nerve damage and amputations.
It is important to understand that these risks result from having high blood glucose levels, not simply from having diabetes.
The American Diabetes Association has set the following blood sugar targets for people with diabetes who are otherwise healthy:
- Fasting blood glucose: 80-130 mg/dL (4.4 – 7.2 mmol/L)
- 2-hour postprandial (post-meal) blood glucose: less than 180 mg/dL (10 mmol/L)
- HbA1c: less than 7% (53 mmol/mol)
These numbers are quite a bit higher than what are considered healthy values for people without diabetes. Healthy people typically have fasting blood glucose levels below 100 mg/dL (5.5 mmol/L) and rarely experience blood glucose above 120 mg/dL (6.7 mmol/L) after eating. Additionally, a normal HbA1c is considered 5.5% (37 mmol/mol) or less.
However, the DCCT trial, which followed more than 1,400 people with type 1 diabetes for nine years, demonstrated that maintaining HbA1c level of 7% (53 mmol/mol) or less was associated with a low risk of diabetes complications.4
Achieving very tight diabetes control in the DCCT trial was associated with an increased risk of hypoglycemic episodes. Thus the reasoning behind the ADA’s more lax targets for blood sugar and HbA1c is to avoid dangerous lows.
This assumes, however, that the only way to reduce blood glucose is by giving more insulin. If you are eating a low-carbohydrate diet to manage your diabetes, this also means you need less insulin and these concerns about hypoglycemia may not apply. This approach appears instead to potentially reduce the risk of hypoglycemia.5
Carb counting vs. low carb for type 1 diabetes
Prior to the discovery of insulin in 1921, many doctors placed their patients with diabetes on very-low-carb diets because they recognized that carbs raise blood glucose much more than either protein or fat.6 While this wasn’t sufficient to manage type 1 diabetes, it did help to prevent extreme carb-related spikes.
The advent of injectable insulin meant that people were able to eat carbohydrate while taking insulin to help control their glucose levels. However, even with insulin, controlling blood glucose levels can be a major challenge for people with type 1 diabetes.
Today, many diabetes educators advise people with type 1 diabetes to eat a low-fat diet and to take insulin to match the amount of carbs they eat in each meal. In fact, many people with type 1 diabetes who use an insulin to carbohydrate ratio have been told, “You can eat whatever you like as long as you take the right dose of insulin.”
However, there are several issues with this approach, including:
- Mistakes with carb estimation. In one study, the carb content of many foods, especially rice, was frequently overestimated or underestimated by children with type 1 diabetes and their parents – as well as by doctors and dietitians.7 This risks too much or too little insulin being given.
- No differentiation between types of carbs. Slowly digested carbs (such as vegetables) can raise blood sugar less and more gradually than rapidly digested carbs (like white bread).8
- Does not take insulin absorption variability into account. Researchers have shown that the amount of insulin absorbed from an injection may vary by as much as 35 percent.9
For many people with type 1 diabetes, eating high-carb foods and taking large doses of insulin can cause blood sugar levels to resemble a rollercoaster rather than remaining within a narrow range – ideally, a relatively straight line.
In his book, Dr. Bernstein’s Diabetes Solution, Dr. Richard K. Bernstein explains that eating very small amounts of slowly-digested carbs and taking very small doses of insulin lead to more predictable results and essentially normal blood sugar levels. He calls this “The Laws of Small Numbers.”
This makes a lot of sense, doesn’t it? Let’s say you estimate that a meal of meat and broccoli contains 25 percent fewer carbs than it actually has (for example, you estimate the meal to have 8 grams of carbs but it actually has 10 grams). You take a dose of insulin that would cover that lower amount of carbs, but you have only 2 grams of carbs that is not matched. Your blood glucose would rise only slightly more than if you had been able to exactly match your carb intake and insulin dosage.
Underestimating the carb content of a high-carb meal by 25 percent can lead to a very different outcome. Many people would consider meat, broccoli, potatoes, milk, and fruit a “healthy” diabetic meal. However, if you take a dose of insulin to cover an estimated 60 grams of carbs rather than the 80 grams the meal actually contains, you’re likely to experience high blood glucose.
Overestimating the carb content of a high-carb meal can lead to a more urgent concern. Again, with a very-low-carb meal, taking slightly more insulin than needed is unlikely to affect blood glucose that much. By contrast, taking significantly more insulin than needed for a high-carb meal may result in hypoglycemia – dangerously low blood glucose that requires immediate treatment to prevent potential loss of consciousness.
Research supporting low carb for type 1 diabetes
Carb restriction for diabetes has mainly been studied in people with type 2 diabetes. However, results from the few studies that have tested this approach in people with type 1 diabetes demonstrate that it can be very effective for them as well:
- In 2016, a small randomized, controlled trial (RCT) – considered the “gold standard” for evidence – found that people with type 1 who limited carbs to 75-100 grams per day for 12 weeks had significant reductions in HbA1c and blood glucose levels compared to those who practiced standard carb counting. Additionally, those who were overweight lost an average of 11 pounds (5 kg ).10
- In 2017, another small RCT found that people with type 1 who ate fewer than 50 grams of carbs per day for 1 week experienced more stable blood sugar control and fewer hypoglycemic episodes than they did during a week of eating 250 grams of carbs and the same number of calories per day.11
- In 2018, a group of doctors and researchers published results from a survey completed by 273 people with type 1 diabetes or parents of children with type 1 diabetes who consumed 30 grams of carbs per day. The group reported exceptional blood glucose control with infrequent hypoglycemic episodes and an average HbA1c of 5.67% (39 mmol/mol).12
- In 2005, Swedish physicians published the results of an educational program for their type 1 diabetes patients that involved consuming 70-90 grams of carbs per day. They reported significant improvements in HbA1c levels, reduction in insulin dosages, and much more stable blood sugar levels throughout the day. One of the most impressive findings was a 94 percent decrease in hypoglycemic episodes after 3 months and an 82 percent decrease at 12 months.13
- In 2011, the same doctors reported that the patients in their program who remained consistently low-carb maintained excellent blood sugar control with an average decrease in HbA1c of 1.8 (20 mmol/mol) after four years.14
Low carb and type 1 diabetes
How many carbs should someone with type 1 diabetes eat every day?
The short answer is that optimal daily carb intake varies among people with type 1 diabetes. As shown in the studies above, restricting carbs to fewer than 100 grams daily is often sufficient to improve blood sugar control and reduce the risk of severe hypoglycemia.
However, a very-low-carb approach (less than 30 grams per day) will require the least amount of insulin, possibly resulting in even more predictable blood sugar control and thus a greater likelihood of remaining within the healthy range throughout the day and night.
How people with type 1 diabetes can safely achieve great blood sugar control with low carb
People with type 1 diabetes who want to start eating low carb should ideally work with a doctor, nurse, dietitian or other health professional who specializes in diabetes and understands carb restriction.
This is because, in addition to decreasing the amount of insulin you take to cover carbs, you may need to make other adjustments, such as reducing your basal insulin dosage. Everyone is unique, and the best and safest approach is one that includes frequent testing, keeping detailed records, and evaluating your results.
For people who use an insulin to carbohydrate ratio (ICR) to calculate their mealtime insulin doses, it is easy to manage a low carb diet as they continue to give the same ratio of insulin to the carbohydrates they eat. So as you eat less carbohydrate, you will automatically inject less insulin.
Some overweight people will lose weight with a low carb diet and become more insulin sensitive. If this occurs, it may be necessary to reduce the insulin to carbohydrate ratio, and probably also the basal insulin doses. Thus regular monitoring of blood glucose levels is important to detect if doses need to be reduced.
For those who have fixed mealtime doses, it is suggested that these should be reduced by 50% when starting a low carb diet.15 Regular monitoring will show if and when further reductions need to be made.
Protein may also need to be accounted for when calculating insulin dosage at mealtimes. Carb-free meals that contain protein have been shown to raise blood glucose, although much more slowly than carb-containing meals do.16
Failing to account for protein may result in excellent blood glucose levels 1-2 hours after a meal but higher levels several hours later. As with carbs, insulin dosage for protein intake varies from person to person, and determining your own body’s needs will take some experimentation. In many people, this effect can be managed by taking a correction dose of insulin at the next mealtime injection.
Alternatively, short-acting insulins can be used with high protein meals. These insulins (such as Actrapid or Humulin R) that have a slower action than rapid-acting analogs such as NovoRapid, Novolog, Apidra or Humalog).
In one of his Diabetes University videos, Dr. Bernstein provides an excellent discussion about how to cover protein with insulin.
Additionally, his books and online resources provide more in-depth and individualized guidance for those who have type 1 and want to transition to a low-carb lifestyle safely.
Addressing concerns about carb restriction for type 1 diabetes
The most common concerns about carb-restricted diets for people with type 1 diabetes are that they are too difficult to maintain, may cause diabetic ketoacidosis (see below), and may increase the likelihood of hypoglycemia.
Firstly, carbohydrate restriction is entirely doable for people with type 1 diabetes. A strict low carb diet maybe too restrictive for some people, but many will be able to sustain a more liberal carb diet in the long term. In addition to Dr. Bernstein, there are many medical and nutrition professionals with type 1 diabetes who have been following a low-carb approach for years with impressive, often life-changing results. Here are just a few who have shared their stories:
- Dr. Ian Lake
- Dr. Ali Lawati
- Dr. Wendy Pogelzelski
- Dr. Troy Stapleton
- Hanna Boethius
- Andrew Koutnik
- Dr. Keith Runyan
- Zein Gajraj
Nutritional ketosis vs. ketoacidosis
Like others who follow very-low-carb diets, people with type 1 diabetes typically go into ketosis. However, it’s important to distinguish between diabetic ketoacidosis (DKA) and nutritional ketosis. DKA is an urgent medical condition in which there is insufficient insulin and blood glucose and blood ketone levels become extremely elevated and a number of other metabolic changes occur that cause dehydration and severe illness.
By contrast, nutritional ketosis is a normal physiological and therefore healthy state in which ketone levels are moderate (less than 3 mmol/l), with normal insulin and blood glucose levels.
As long as people with type 1 diabetes monitor their blood glucose levels regularly and take insulin as needed, being in nutritional ketosis does not appear to increase the risk of DKA.17
Acute illness and ketoacidosis
Note also that the need for insulin – regardless of which foods you eat – increases with acute illness. It is not uncommon for dangerous ketoacidosis to occur in connection with, for example, stomach illness during which you don’t eat and therefore may forget to take your insulin.
The same applies if you eat a low-carb diet. Your insulin requirement may increase with illness and so if you normally take low doses it is extra important to understand you will need more insulin during periods of illness. Omitting to increase insulin when ill may be the greatest risk with low-carbohydrate diets and reduced insulin doses.
Fears of hypoglycemia often stem from results of the DCCT study, which found that although lower HbA1c and tighter glycemic control helped reduce the risk of developing diabetes complications, it also increased the incidence of hypoglycemia.18
However, in that study, people were taking relatively large doses of insulin in order to achieve tight blood glucose targets.
Carb restriction enables people with type 1 diabetes to get the benefit of tight blood glucose control without taking large quantities of insulin.
As discussed by the people with type 1 diabetes above and hundreds of others who have shared their stories – and confirmed in several studies – the severity and frequency of hypoglycemic events can dramatically decrease after transitioning to a low-carb diet (provided that insulin doses are reduced appropriately).
Specific advice for low-carb eating in type 1 diabetes
Total carbs vs. net carbs
At Diet Doctor, we generally recommend counting only the digestible (net) carbs in whole foods. Dr. Bernstein recommends that people with type 1 diabetes count some or all of the fiber, as high-fiber foods cause more distension of the stomach that may trigger the release of hormones that can raise blood sugar. 19 It is important to be aware that there are no published studies that have discussed this effect. However, some people with type 1 diabetes have confirmed that counting at least a portion of fiber in foods works best when calculating insulin dosages.
Eat more protein and healthy fat
Many people with type 1 diabetes are not overweight and so it is important to ensure you take enough calories in your meals. So, if you reduce the amount of carbs, you will likely need to increase the amount of other foods, such as protein and healthy fats, to avoid going hungry. Protein is derived from meat, fish, eggs and dairy foods.
Plant sources of protein include legumes (beans and pulses) and nuts. Protein can cause a delayed rise in blood glucose and may need to be covered by insulin. Protein provides essential amino acids, helps build and maintain muscle, and is involved in creating hormones, among other functions. It is an extremely important nutrient and one that shouldn’t be skimped on – indeed you may need a larger portion that previously.
Fat has had a bad reputation as we have been told it increases our risk of heart disease. However many fats are recognized by everyone to be healthy, particularly unsaturated fats found in plants, oily fish and meat. Attitudes are also changing about saturated fats (found in dairy and meat), and are no longer regarded as always unhealthy.
The main danger with fats relates to trans-fats, which are artificially manufactured and found mainly in highly-processed foods. Eating good quality, unprocessed or minimally processed fat-containing foods can ensure you maintain a healthy calorie intake when using a low-carb approach. Fat increases satiety and reduces hunger between meals, making it less likely you will be tempted by high-carb snacks.
Treat hypoglycemia appropriately
Although episodes of hypoglycemia can be minimized with a low-carb approach, occasional lows are inevitable for people with type 1 diabetes. Regardless of the type of diet you follow, fast-acting carbohydrate (such as glucose tablets) is required in order to raise blood glucose to a safe level.
However, bear in mind that if you are using low carb, you are likely to have less insulin in the bloodstream and you may find that taking the recommended 15 grams of glucose increases your blood glucose too much. It may take some experimentation to determine the exact amount you need. Some people with type 1 diabetes who eat low carb report that taking a single glucose tablet (about 4 grams of carbs) is enough to quickly raise their blood sugar up to the healthy range.
Low-carb type 1 diabetes support and resources
Dr. Bernstein’s Diabetes Solution (Read several chapters of his book online)
Individualized guidance from type 1 health professionals
Ketogenic Diabetic Athlete (Dr. Keith Runyan)
SVV Nutrition (Sean Vander Veer, Registered Dietitian)
Kelly Schmidt Wellness (Kelly Schmidt, Registered Dietitian)
DiaVerge Diabetes (Lisa la Nasa, Certified Level 2 Diabetes Paraprofessional)
Low carb: benefits and limitations
It cannot be overemphasized that many things besides food can affect blood glucose levels, including stress, illness, increased physical activity and even seemingly mild alterations in sleep. By definition, many of these things are difficult or even impossible to prevent. Therefore, the most important thing when it comes to managing type 1 diabetes is to understand how these things can affect your glucose control.
If it is something you can predict, such as planned increased activity, then you can make adjustments to your insulin dose to prevent it affecting your glucose level. If not, then it is important to know how to respond to an unexpected low or high glucose reading. Frequent testing is key and makes it much easier to manage these effects on your glucose levels.
Fortunately, a low-carb diet can help you avoid big changes in glucose levels related to food, and simplifies mealtime insulin dosing so that a huge piece of the diabetes puzzle is no longer an issue. This can significantly improve your overall diabetes control, reduce anxiety, and enhance your quality of life.
Common questions and answers
I have to eat carbohydrates regularly or I’ll suffer a hypo.
The only reason for a hypo is if there is too much insulin in your system. So if you continue to take the same doses of insulin as you do now, you will experience hypos when you reduce the carbs you eat. However, if you reduce the insulin doses to match the reduced carb intake, hypos will not happen.
The question is: Should you allow insulin to control your life, or would you be willing to adjust insulin doses to fit the life you lead?
Won’t increasing the fat in my diet increase my risk of heart disease?
Type 1 diabetes is exclusively a deficiency in insulin production, which makes it difficult to control blood glucose. High blood glucose levels over a long period of time causes complications such as heart disease, blindness, failing kidney failure and amputations.
If you normalize your blood glucose with the help of a low-carbohydrate diet and adjusted insulin doses, the risk of long-term complications will likely be reduced significantly.
Learn more about type 1 diabetes
Asia Pacific Journal of Clinical Nutrition 2016: A randomised trial of the feasibility of a low-carbohydrate diet vs standard carbohydrate counting in adults with type 1 diabetes taking body weight into account. [moderate evidence]
Diabetes, Obesity and Metabolism 2017: Short-term effects of a low-carbohydrate diet on glycaemic variables and cardiovascular risk markers in patients with type 1 diabetes: A randomized open-label crossover trial [moderate evidence]
Diabetes, Obesity and Metabolism 2017: Short-term effects of a low-carbohydrate diet on glycaemic variables and cardiovascular risk markers in patients with type 1 diabetes: A randomized open-label crossover trial [moderate evidence]
Asia Pacific Journal of Clinical Nutrition 2016: A randomised trial of the feasibility of a low-carbohydrate diet vs standard carbohydrate counting in adults with type 1 diabetes taking body weight into account. [moderate evidence] ↩
Diabetes, Obesity and Metabolism 2017: Short-term effects of a low-carbohydrate diet on glycaemic variables and cardiovascular risk markers in patients with type 1 diabetes: A randomized open-label crossover trial [moderate evidence] ↩
Experimental and Clinical Endocrinology & Diabetes 2010: Skipping meals or carbohydrate-free meals in order to determine Basal insulin requirements in subjects with type 1 diabetes mellitus? [non-controlled trial; weak evidence] ↩
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The main fear about lower-carb and higher-fat diets have always been an increase in the risk of heart disease. However, interventional studies so far indicate that if anything the risk appears to decrease:
- British Journal of Nutrition 2016: Effects of low-carbohydrate diets v. low-fat diets on body weight and cardiovascular risk factors: a meta-analysis of randomised controlled trials. [strong evidence for improved risk factors]
- PLOS ONE 2015: Dietary intervention for overweight and obese adults: comparison of low-carbohydrate and low-fat diets. A meta-analysis. [strong evidence for improved risk factors]
- Obesity reviews 2012: Systematic review and meta‐analysis of clinical trials of the effects of low carbohydrate diets on cardiovascular risk factors [strong evidence for improved risk factors]
- Circulation 2010: Dietary intervention to reverse carotid atherosclerosis [moderate evidence for a reduction in atherosclerosis]