Starting low carb or keto with diabetes medications
, medical review by Dr. Michael Tamber, MD
Evidence based
For instance, we want you to know that it’s very important to adjust diabetes medications when starting a low-carb diet. In particular, insulin doses may need to be lowered to avoid low blood sugar, and SGLT-2 inhibitors may need to be discontinued (see below).
We want you to discuss any changes in medication and lifestyle with your doctor before making any such changes. Full disclaimer
So you have diabetes and want to try eating low carb or keto? Good for you! Making these dietary changes has the potential to reverse type 2 diabetes.
However, you need to know what you are doing, and you need to communicate frequently with your healthcare team. Once you start eating low carb you will likely have to lower your insulin doses as well as the doses of other diabetes medications, frequently by quite a lot.
Avoiding the carbohydrates that raise your blood sugar decreases your need for medication to lower it. Taking the same dose of insulin or insulin-stimulating oral medication as you did prior to adopting a low-carb diet might result in low blood sugar, something that can be dangerous.
You need to test your blood sugar frequently when starting this diet and adjust your medication accordingly. This should always be done with the assistance of a physician or other health professional with expertise in diabetes (find a low-carb doctor).
No drugs
If you have diabetes and you’re treated by diet alone, there is an extremely low risk of low blood sugar on low carb. You can get started right away.
Insulin-treated type 2 diabetes
As a general rule, you will need to lower your doses when starting a strict low-carb diet.
Work with your doctor to find the right initial reduction. Many find they need to reduce long acting insulin between 30 and 50%.
If you remain low carb, it is possible you will be able to stop mealtime insulin altogether. If your blood sugar levels continue to drop off the mealtime insulin, you can then begin to more aggressively reduce your long-acting insulin. As blood sugars stabilize in the normal range, you may be able to continue weaning the insulin, as long as glucose levels continue to be normal.
Note that many physicians feel it is safer to decrease insulin doses by too much rather than not enough. This is because taking too much insulin can result in a low blood sugar level, which has the potential to be acutely dangerous. On the other hand, having slightly high blood sugars for short periods of time is usually not going to have major health consequences.
In addition, frequent low blood sugars lead to eating or drinking glucose or another form of rapid-acting carbohydrate in order to raise your glucose to a safe level. These extra calories may very well thwart your efforts at weight loss.
Insulin in type 1 diabetes
Much of the above advice about insulin also applies to people with type 1 diabetes, with the critical difference that people with type 1 will not be able to discontinue insulin entirely. Nonetheless, a low-carb, high-fat diet can be fantastic for empowering people with type 1 diabetes to smooth out their wide swings in blood sugar.
However, eating low carb with type 1 diabetes requires even greater attention to blood sugar levels and insulin adjustment, and an even closer working relationship with your healthcare team.
Many people with type 1 diabetes use an insulin to carbohydrate ratio (ICR) to calculate their mealtime insulin doses. If using an ICR while eating a low-carb diet, you may continue to give the same ratio of insulin to the carbohydrates you eat. But, as you eat fewer carbs, you will be injecting less insulin overall.
In some cases, the amount of insulin required for meals will not decrease as much as would be expected for the lower carb intake; this is presumably due to the potential of higher protein intakes to increase gluconeogenesis (the production of “new sugar” by the liver).
People who use relatively fixed mealtime doses of insulin, or those on premixed insulin twice daily, should use a similar approach to those with type 2 diabetes. Again, the critical difference is that people with type 1 diabetes will always need some insulin, even on a very low-carbohydrate diet.
It is important to be aware that a diet with less than 50 grams of carbs each day can lead to ketosis, a normal physiological state that results from the body burning fat for energy. This should not be confused with ketoacidosis, a dangerous complication of type 1 diabetes that can occur when there is insufficient insulin.
Because people with type 1 diabetes are at risk of progressing from physiologic ketosis to dangerous ketoacidosis, we recommend that they start with a more liberal low-carb diet, containing at least 50 grams of carbs per day.
We do not recommend starting a ketogenic low-carb diet (below 20 grams a day) unless you’re certain of how to manage this risk and are working closely with a very experienced healthcare practitioner. You have to be able to test your ketones often, using extra care if you feel even slightly ill, practice intermittent fasting, or have been exercising.
Type 1 diabetes – how to control your blood sugar with fewer carbs
Insulin-releasing pills
Some pills for type 2 diabetes work by directly stimulating the pancreas to produce more insulin. These medications increase the risk of low blood sugar on a low-carb diet.
The most common examples of these pills would be in the class known as sulfonylureas (e.g. glimepiride, gliclazide, glipizide, glibenclamide, glyburide, tolbutamide, etc.), while the class known as meglitinides (e.g. repaglinide and nateglinide) is used less often.
You will need to reduce the dose or stop these drugs when starting a low-carb diet in order to avoid low blood sugar levels.
Metformin
Individuals with type 2 diabetes can can safely take metformin on a low-carb diet. There is a very low risk of low blood sugar from taking metformin.
GLP-1 agonists and DPP-4 inhibitors
GLP-1 agonists typically have generic names ending in -tide like semaglutide, liraglutide, or exenatide. DPP-4 inhibitors typically have generic names ending in -gliptin like sitagliptin or linagliptin.
These drugs should rarely lead to low blood sugar on a low-carb diet, by themselves.
SGLT-2 inhibitors
SGLT-2 inhibitors have generic names ending in -gliflozin, like canagliflozin, empagliflozin, and dapagliflozin. These drugs lower blood sugar by causing the kidneys to excrete more glucose into the urine. However, they can increase the risk of a dangerous condition called euglycemic ketoacidosis.
The risk of euglycemic ketoacidosis may also be increased by a strict low-carb diet.
It’s worth noting that when ketoacidosis occurs while taking an SGLT-2 inhibitor, the blood sugar level is not necessarily high, making it harder to detect.
If you get symptoms of ketoacidosis – extreme thirst, nausea, vomiting, stomach pain, confusion, etc. – you should stop the medication and contact a doctor immediately.
Learn more
More
A keto (strict low-carb) diet for beginners
Low carb for doctors
Are you a doctor or do you know one? Here’s our low carb for doctors resource, with information on how to safely handle medications on a low-carb diet: