Adrenaline, more commonly known to doctors as epinephrine, is a hormone that is important to the body's metabolism. Heightened secretion of epinephrine from the adrenal gland is caused by fear or anger and it prepares the body to meet emergencies such as cold, fatigue, and shock by increasing heart rate and the hydrolysis of glycogen to glucose. This reaction, often called the "fight or flight" response, prepares the body for strenuous activity.

Epinephrine is used medicinally in cardiac arrest to stimulate heart rate. It is also used to treat bronchial asthma, acute allergic reactions, emphysema and the treatment of the eye disease glaucoma.