Long-Acting Basal Insulins

The liver releases glucose between meals and overnight. Long-acting basal insulin analogues—insulin glargine, detemir, and degludec—supply background insulin that restrains this hepatic glucose output. Their main clinical effect is lower, more stable fasting blood glucose. Basal insulin is not meal insulin. It cannot reliably cover a carbohydrate-heavy meal or rapidly correct a post-meal glucose rise. A patient whose fasting readings are in range but whose after-meal readings remain high may need evaluation of meals or prandial therapy; simply increasing basal insulin can create overnight or between-meal hypoglycemia. A well-matched basal dose improves the fasting pattern without causing unexplained lows when the patient has not eaten.