Adjunctive antihyperglycaemic drugs for adults with type 1 diabetes

Use of antihyperglycaemic drugs as an adjunct to insulin to treat adults with type 1 diabetes is not recommended; this practice is off-label and use requires specialist supervision¹. Insulin treatment should never be stopped in patients with type 1 diabetes.

Adjunctive antihyperglycaemic drugs that have been trialled with insulin in patients with type 1 diabetes are:

• metformin—reduction of glycated haemoglobin (HbA1c) is not sustained and effect on weight reduction is modest. No benefit on long-term cardiovascular outcomes has been seen.
• sodium-glucose co-transporter 2 (SGLT2) inhibitors—these can reduce HbA1c and insulin requirements, and cause weight loss. However, long-term cardiovascular outcomes have not been assessed in type 1 diabetes, and there is a significant risk of diabetic ketoacidosis (DKA). DKA may occur without hyperglycaemia, especially if the insulin dose is reduced by more than 20% (see here for information on SGLT2 inhibitors and DKA). If an SGLT2 inhibitor is used under specialist supervision:
  • a plan for sick-day management and monitoring of blood ketones should be in place
  • SGLT2 inhibitors should be withheld periprocedurally (see Periprocedural management of adults with type 2 diabetes).
• glucagon-like peptide-1 (GLP-1) receptor agonists—weight loss can be achieved but improvement in HbA1c is unlikely to be clinically relevant, and there is an increased risk of hypoglycaemia and hyperglycaemia with ketosis.