Glucagon is a hormone that plays a crucial role in regulating blood glucose levels. It acts as a counter-regulatory hormone to insulin, meaning it has the opposite effect. Here's how:

* Increases blood glucose levels: Glucagon stimulates the liver to break down stored glycogen into glucose and release it into the bloodstream, thus raising blood sugar.

* Promotes gluconeogenesis: Glucagon also promotes the production of new glucose from non-carbohydrate sources, such as amino acids and glycerol.

In short, glucagon helps to increase blood glucose levels when they are low, ensuring a constant supply of energy for the body.