Glucagon is usually given in an emergency to people with insulin-dependent diabetes who develop very low blood sugar levels and pass out or are unable to take some form of sugar by mouth. Glucagon injection or nasal powder (Baqsimi) increases low blood sugar levels back to normal.

Confusion, incoherent speech, coordination difficulties, agitation, or un-cooperation are signs that blood sugar levels are getting very low in people with diabetes treated with insulin. Ideally people should be given some form of quick acting sugar as soon as these symptoms occur, followed by a longer acting carbohydrate such as a sandwich. Passing out (becoming unconscious) and seizures are a sign of extremely low levels. This is usually when glucagon by injection is given because it can be dangerous or impossible to give something by mouth.

Blood sugar levels can get low when people with diabetes treated with insulin forget to eat, or do not eat enough food to balance the effects of the insulin, or if they do more physical activity than intended.
Glucagon injection kits are made for home use and have everything you need inside them to give an emergency injection of glucagon if somebody’s blood sugar level drops below 50 mg/dL (you can measure this using their blood glucose monitor).

Glucagon works by stimulating the release of stored glucose from the liver, by spurring the liver to make more glucose, and by reducing how much glucose the liver needs to function.
Glucagon also acts on adipose (fat) tissue to increase the breakdown of fat stores into the bloodstream, which releases glucose and fatty acids as energy sources.

Glucagon injection is also used as a diagnostic aid to relax the muscles of the stomach and bowel during X-rays of the Gastrointestinal tract.