Glucagon. Hypodermic syringe with two bottles of glucagon, a hormone drug used to treat cases of heart failure and diabetics who are suffering from low blood sugar levels (hypoglycaemia). Glucagon is a polypeptide hormone produced naturally by alpha-cells in the islets of Langerhans in the pancreas. It causes an increase in blood sugar levels, the release of several other hormones and an increase in the strength of the heart's contractions. Use of glucagon may cause nausea and vomiting. Diabetics may suffer from hypoglycaemia if they take too much insulin, exercise too much or do not eat enough. Hypoglycaemia can cause weakness, dizziness and unconsciousness.