An injectable form of glucagon may be part of first aid in cases of low blood sugar when the person is unconscious or for other reasons cannot take glucose orally or by intravenous.

[15] The glucagon is given by intramuscular, intravenous or subcutaneous injection, and quickly raises blood glucose levels.

The reconstitution process makes using glucagon cumbersome, although there are a number of products now in development from a number of companies that aim to make the product easier to use.Anecdotal evidence suggests a benefit of higher doses of glucagon in the treatment of overdose with beta blockers; the likely mechanism of action is the increase of cAMP in the myocardium, in effect bypassing the β-adrenergic second messenger system.

[17] Glucagon relaxes the lower esophageal sphincter and may be used in those with an impacted food bolus in the esophagus ("steakhouse syndrome").

[22][23] Glucagon's effect of increasing cAMP causes relaxation of splanchnic smooth muscle, allowing cannulation of the duodenum during the endoscopic retrograde cholangiopancreatography (ERCP) procedure.

[25] While glucagon can be used clinically to treat various forms of hypoglycemia, it is contraindicated in patients with pheochromocytoma, as it can induce the tumor to release catecholamines, leading to a sudden elevation in blood pressure.

[4] Likewise, glucagon is contraindicated in patients with an insulinoma, as its hyperglycemic effect can induce the tumor to release insulin, leading to rebound hypoglycemia.

This regulates the reaction catalyzing fructose-2,6-bisphosphate (a potent activator of phosphofructokinase-1, the enzyme that is the primary regulatory step of glycolysis)[28] by slowing the rate of its formation, thereby inhibiting the flux of the glycolysis pathway and allowing gluconeogenesis to predominate.

[29] In the 1920s, Kimball and Murlin studied pancreatic extracts, and found an additional substance with hyperglycemic properties.

[31] A more complete understanding of its role in physiology and disease was not established until the 1970s, when a specific radioimmunoassay was developed.