Table 1.

Overview of the most frequently prescribed glucose-lowering medications to treat type 2 diabetes mellitus

Medication (route of administration)	Mechanism of action	HbA1c reduction (mmol/mol)	Benefits	Common side effects and disadvantages
Metformin (oral)	Reduces intestinal glucose absorption. Reduces hepatic glucose production. Increases insulin sensitivity.	11	Cheap. Effective. No hypoglycaemia. Long-term safety profile.	Diarrhoea, headache, change in taste. Caution with impaired renal function. Low risk of lactic acidosis.
GLP-1 receptor agonist (subcutaneous injections and oral)	Similar to the gut hormone (incretin) GLP-1. Stimulates pancreatic beta cells to release insulin (glucose-dependent). Reduces beta cell apoptosis. Inhibits glucagon secretion. Slows down gastric emptying. Promotion of satiety.	13–20	Glucose-dependent effect. No hypoglycaemia. Weight loss. Reduction of cardiovascular events in patients with cardiovascular risk factors.	GI symptoms (decrease on longer use). High costs.
DPP-4 inhibitor (oral)	Inhibits DPP-4, the enzyme breaking down GLP-1.	7–9	No hypoglycaemia. Minor weight loss.	Rare: pancreatitis. No effect on hard cardiovascular endpoints.
SGLT2 inhibitor (oral)	Prevents glucose reabsorption in the kidney (proximal convoluted tubules).	7–9	Hypoglycaemia is rare. Reduces cardiovascular mortality and morbidity.	Genital infections.
Sulfonylurea derivative (gliclazide preferred) (oral)	Stimulates pancreatic beta cells to produce insulin (independent of glucose levels).	17	Cheap. Effective oral treatment.	Weight gain. Risk of hypoglycaemia.
Insulin (subcutaneous injections)	Stimulates glucose uptake in fat and skeletal muscle. Stimulates glycogen synthesis. Inhibits hepatic glycogenolysis and gluconeogenesis. Inhibits lipolysis.	Dose-dependent	Most effective for severe hyperglycaemia. Quick effect.	Weight gain. Risk of hypoglycaemia. Injection-related complications.

DPP-4, dipeptidyl peptidase-4; GLP-1, glucagon-like peptide-1; HbA1c, haemoglobin A1c; SGLT2, sodium-glucose cotransporter 2.