What it means
Glucagon comes from alpha cells in the pancreas. When blood sugar falls, such as between meals or overnight, glucagon signals the liver to break down stored glycogen and to make new glucose. Insulin does the opposite, so the two hormones keep blood sugar in range together.
In type 2 diabetes, glucagon is often too high after meals, which adds to high blood sugar. Natural GLP-1, and the medicines that copy it, lower glucagon release when blood sugar is high. That is one of the ways they improve blood sugar.
Some newer medicines in development also act on the glucagon receptor, aiming to increase calorie burn or reduce liver fat. Those are drugs, not the hormone itself.
Glucagon is also given as an emergency treatment for severe low blood sugar. People who use insulin may be prescribed a glucagon kit or nasal spray for this purpose.
Why it matters
Lowering excess glucagon is part of how GLP-1 medicines improve blood sugar in type 2 diabetes.