Adapting diabetes medication for low carbohydrate management of type 2 diabetes: a practical guide

Sulphonylureas and meglitinides

Sulphonylureas (for example, gliclazide) and meglitinides (for example, repaglinide) should be reduced or stopped when an LCD is commenced. An initial dosage reduction of at least 50% is typically appropriate, with further reductions according to blood glucose response. There may be a period of short-term hyperglycaemia while the individual adapts to an LCD.

Insulins

Practical expertise suggests a 50% reduction of daily insulin dose at initiation of the LCD is appropriate in most cases. In individuals whose HbA1c is markedly elevated, a smaller reduction of perhaps 30% may be appropriate, with further reductions over time. For individuals on a basal-bolus regimen it is preferential to reduce or stop bolus insulin. In individuals on a mixed insulin or basal insulin alone each dose can be reduced by 30–50% at the start of LCD. Some patients can expect to come off insulin completely, over days or months, as insulin resistance resolves. Improving blood glucometer readings can guide the down-titration of insulin.

It should be cautioned that some patients may have an insulin insufficiency form of diabetes, such as latent autoimmune diabetes of adults. Although the LCD enables a reduction in insulin dosage it should not be completely stopped in this cohort of patients. Endogenous insulin insufficiency is more likely in patients who were not overweight at the time of diagnosis of diabetes, and it may be present in some with longstanding T2D. Over-reduction in insulin dosage in these patients would lead to significant hyperglycaemia, and thus further dosage reduction would be avoided. It is recommended that additional investigation and expert advice is sought in cases of doubt as per good medical practice.

SGLT2 inhibitors (‘flozins’)

These carry a risk of causing ketoacidosis if a patient has significant insulin insufficiency, with any diet. SGLT2i-induced ketoacidosis may occur with a normal blood glucose, which heightens the risk of the life-threatening condition going unrecognised. Consider the possibility of insulin insufficiency, including in those who could have been misdiagnosed with T2D. In a community setting, for safety and simplicity, it may be appropriate for most patients to stop their SGLT2i when an LCD is initiated. This removes the SGLT2i-induced ketoacidosis risk, and additionally the effectiveness of the LCD means the benefit of a SGLT2i is diminished. (Note: a very LCD, typically <30–50 g carbohydrate/day, can produce a physiologically normal state of ketosis, which should not be confused with the pathological state of ketoacidosis.)

Metformin

This is safe to continue and in some patients metformin continues to offer favourable benefits. Up to 25% of patients experience gastrointestinal side effects from metformin.

GLP-1 agonists (‘-enatide’, ‘-glutide’)

These are safe to continue, with the beneficial actions of increased satiety and slowed gastric emptying, and possibly cardiovascular benefit. With a sustained LCD patients may be able to stop their GLP-1 agonist.

Thiazolidinediones (‘glitazones’)

These are safe to continue from a short-term perspective. Concerns exist over their long-term safety including: bladder cancer, heart failure, and bone mineral density. Thiazolidinediones are also known to cause weight gain. It is recommended to stop thiazolidinediones as soon as blood glucose levels allow.

DPP-4 inhibitors (‘gliptins’)

These are safe to continue. However, clinical experience agrees that these seem to have little blood glucose-lowering effect in the context of an LCD.

Acarbose

This is safe to continue. But, on commencing an LCD the reduced starch ingestion means the patient can usually stop acarbose.

Blood glucose testing strips

Structured self-monitoring of blood glucose, such as paired pre- and post-meal testing, can be very helpful by providing rapid feedback on how foods affect blood glucose as a patient adopts an LCD, and to inform whether medication doses can be reduced further. Patients on drugs that risk hypoglycaemia should have access to adequate testing strips.