How does glucagon affect blood sugar levels in diabetes?

Increases. Glucagon increases blood sugar in diabetes or in anyone.
Goes up when needed! Glucagon is known as a 'counter-regulatory' hormone. This means it counteracts another hormone's action. In this case, glucagon works to help release glucose from the liver. This is very imporant between meals, when a steady supply of glucose is neeed for the body's ongoing needs. It also helps when a hypoglycemic reaction is occurring, helps bring glucose to the rescue from the liver.

Related Questions

How do insulin and glucagon control blood sugar levels?

Opposite action. Insulin will deliver glucose to the cells of your body and has the potential to cause hypoglycemia. In the presence if hypoglycemia or with fasting, glucagon is the hormone secreted which will stimulate glycogen (stored glucose) conversion to glucose in order to keep body fuel supply going.