Glucagon: What It Is and How the Rescue Hormone Works

At a glance

What is glucagon?

Glucagon is a 29-amino-acid hormone made by the pancreas that works opposite to insulin: when blood sugar drops, glucagon raises it. As a medicine it is the emergency rescue treatment for severe hypoglycemia, the dangerous low-blood-sugar episodes that can occur in people with diabetes, especially those on insulin. It is sold as the ready-to-use Gvoke injector and Baqsimi, a nasal powder, among other products. The GlucaGen HypoKit emergency kit was discontinued in the U.S. in 2024.

How does glucagon work?

Glucagon binds glucagon receptors on liver cells and switches on the pathways that release glucose. It stimulates glycogenolysis, the breakdown of stored glycogen into glucose, and gluconeogenesis, the making of new glucose, so the liver pushes glucose into the bloodstream and blood sugar rises within minutes. This is why it works as a rescue treatment when someone with hypoglycemia is unable to eat or drink. Because the effect depends on the liver having glucose stores to release, glucagon can be less effective when those stores are depleted, such as in prolonged fasting or starvation. Glucagon also relaxes the smooth muscle of the gastrointestinal tract, which is the basis of its separate use as a diagnostic aid during certain imaging studies. In a trial in adults with type 1 diabetes, a nasal powder formulation raised blood glucose about as effectively as injected glucagon, with the practical advantage of needing no injection or mixing in an emergency.

Is it FDA-approved?

Yes. Glucagon is approved for severe hypoglycemia and as a diagnostic aid for gastrointestinal imaging. The table shows when each product was approved:

What is glucagon prescribed for?

Glucagon is prescribed as emergency treatment for severe hypoglycemia in people with diabetes, typically given by a caregiver when the person cannot safely take sugar by mouth. Injectable forms are also used to relax the gut during radiologic procedures. It is contraindicated in pheochromocytoma (a catecholamine-producing tumor) and in insulinoma.

What are the side effects?

According to the injectable and nasal powder labels, common side effects include:

• Nausea and vomiting
• Headache
• Injection-site reactions, or nasal and eye symptoms with the nasal powder More serious considerations include:
• A sharp rise in blood pressure in people with pheochromocytoma
• Low blood sugar rebound in people with insulinoma
• Rare allergic reactions

Evidence strength

FDA approved: Glucagon is FDA-approved for severe hypoglycemia and as a diagnostic aid, supported by long clinical use and trials of its injectable and nasal forms.

Sources: FDA prescribing information for GlucaGen, Gvoke, and Baqsimi; a randomized trial of nasal glucagon in adults with type 1 diabetes (Rickels et al., Diabetes Care, 2016, DOI: 10.2337/dc15-1498), indexed on PubMed. This document is educational and does not constitute medical advice.