Medication Adjustments for Low Carb Diets

Short term studies in people with type 1 diabetes have shown that low carbohydrate diets lead to improvements in A1C levels, reduced insulin requirements, less glucose variability, and weight loss. People with type 2 diabetes have shown similar improvements when compared to higher carbohydrate diets or low fat diets. Some also show higher rates of diabetes remission, improved triglyceride levels and a reduced need for medication in the short term.

It is unknown if the improvements seen will be maintained long-term or will result in lower rates of cardiovascular disease or other diabetes complications or mortality. Many studies are limited by poor research quality, so we aren’t able to provide general recommendations for everyone living with diabetes.

Many people have difficulty following low carbohydrate diets for the long term. Even so, given the popularity of low carbohydrate diets amongst the public, it’s common for people to at least profess the desire to start one.

Definitions

Moderate Carbohydrate: >130 g carb/d, 26 – 45% of total energy from carb (Mean ~200 g/d)

Low Carbohydrate: <130 g carb/d, <26% of total energy from carb

Ketogenic: 20 – 50 g carb/d, <10% of total energy from carb

Nutritional Considerations

Note that patients should be strongly encouraged to have a review with a dietitian to ensure that they are getting adequate nutrition, if following a low carbohydrate or ketogenic diet.

Ketones

In research trials including people with type 2 diabetes, mean blood ketone levels have ranged between 0.3 to 0.5 mmol/L, and urine ketones usually don’t go above trace. If you’re concerned that your patient on a ketogenic diet has excessive ketone levels, ask them to check and ensure that blood ketones are no great than 0.8 mmol/L (ideally < 0.6 mmol/L).

Hypoglycemia

People who are following a ketogenic diet and taking insulin or an insulin secretagogue, are strongly encouraged to treat hypoglycemia with fast acting carbohydrate, even if that means their ketone levels will drop over the short term.

Medication Changes and Precautions

Changes to medications might be required for patients who start following a low carbohydrate or ketogenic diet. Consideration should be given to their current carbohydrate intake, how much reduction in carb intake is anticipated and the current glycemic control. The following medication adjustments should be considered, as appropriate:

Medication	Concern	Adjustment to consider
Insulin	Risk of hypoglycemia	Reduce or stop depending on glycemic control and type of diabetes. Insulin should not be stopped completely in insulin deficient diabetes (Type 1, LADA, longstanding Type 2 diabetes). Consider weaning by 30 - 50%: ∙ Basal alone: 30–50% reduction ∙ Basal-bolus: 30-50% reduction in bolus insulin ∙ Mix insulin: 30-50% reduction
Sulfonylurea or Megitinide	Risk of hypoglycemia	Reduce or stop depending on glycemic control. Consider successive halving of dose
SGLT2 inhibitor	Increased glucosuria, risk of euglycemic ketoacidosis	No routine medication adjustment, but ensure that the patient knows how to adjust for sick days, and knows the signs and symptoms of DKA. For people with type 1 diabetes, instruct them on how to prevent DKA when on an SGLT2 inhibitor
Glucagon	May not be as effective to treat hypoglycemia	If following a ketogenic diet, people taking insulin should monitor glucose more frequently in situations when there's increased risk of hypoglycemia
Metformin	Safe, and may provide clinical benefits	Optional. Consider clinical pros and cons.
GLP1 receptor agonist	Safe, and may provide clinical benefits (satiety and cardiovascular)	Optional. Consider clinical pros and cons.
Thiazolidenedione	Safe on a low carb diet. Consider known possible side effects.	Optional. Consider clinical pros and cons.
DPP4 inhibitor	Safe, but likely little glycemic benefit	Optional. Consider clinical pros and cons.
Alpha glucosidase inhibitor	Safe, but likely little glycemic benefit	Usually stop because there's no benefit, as few disaccharides with low carb diet.