Long-Acting Basal Insulins

Insulin glargine, detemir, and degludec are long-acting basal insulin analogues. Their purpose is to provide a relatively steady background insulin supply between meals and overnight. The liver releases glucose continuously, even when a person is asleep or has not eaten. Basal insulin restrains that hepatic glucose output, so its strongest effect is on fasting blood glucose. It is not designed to cover a meal, rapidly correct marked hyperglycaemia, or treat diabetic ketoacidosis. A useful distinction is this: prandial insulin manages the glucose arriving from food; basal insulin manages the glucose the liver keeps releasing in the background. A person can have acceptable pre-meal readings yet wake with high fasting glucose when basal coverage is inadequate. Long-acting analogues have less of a pronounced peak than shorter-acting insulin. That reduces, but does not eliminate, hypoglycaemia risk. A low glucose several hours after an evening dose may still be caused by excessive basal insulin, especially when the patient has reduced intake, renal impairment, or an unrecognized nocturnal low.