Overview
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In plain language
Glucagon is a natural hormone made by the pancreas. It is a chain of 29 amino acids, and it does the opposite of insulin: it tells the liver to release stored sugar into the blood.
As a medicine, glucagon is an emergency rescue for dangerously low blood sugar in people with diabetes. It comes as an injection, an autoinjector and a nasal spray. Doctors also use it to relax the gut during some imaging tests.
For students
Glucagon is a 29-residue peptide (about 3,483 Da) secreted by pancreatic alpha cells when blood glucose falls. It binds the glucagon receptor, a class B GPCR on hepatocytes, raising cAMP and driving glycogenolysis and gluconeogenesis.
It comes from proglucagon, the same precursor that intestinal L cells process into GLP-1 and GLP-2. Glucagon was discovered in 1923 by Kimball and Murlin as a hyperglycemic contaminant of early insulin extracts.
For researchers and instructors
Therapeutics. Rescue products include reconstituted glucagon, ready-to-use liquid glucagon, the analogue dasiglucagon, and intranasal glucagon. Effectiveness requires liver glycogen stores.
Metabolic pharmacology. Glucagon also increases energy expenditure and hepatic fat oxidation. This is why glucagon-receptor activity is included in new multi-agonists such as retatrutide.
Pathophysiology. Inappropriately high glucagon contributes to hyperglycemia in type 2 diabetes. Glucagonomas cause a rash called necrolytic migratory erythema.
Status. FDA-approved for severe hypoglycemia and as a diagnostic aid.
Molecular identity
- Amino acids
- 29
- Molecular weight
- ~3,482.8 Da
- Formula
- C₁₅₃H₂₂₅N₄₃O₄₉S
- Sequence
- HSQGTFTSDYSKYLDSRRAQDFVQWLMNT
Sequence map
Hydropathy
Kyte–Doolittle score per residue. Positive values are water-repelling.
Origin and history
Glucagon was discovered in 1923, only a year after insulin. Charles Kimball and John Murlin at the University of Rochester noticed that early insulin extracts briefly raised blood sugar before lowering it, and traced this to a second substance they named glucagon, for “glucose agonist.”
Its 29-amino-acid sequence was worked out in 1956 by William Bromer and colleagues at Eli Lilly. In 1975 Roger Unger argued that diabetes involves too much glucagon as well as too little insulin, a view that later shaped drugs like retatrutide. Glucagon is used as an emergency treatment for severe low blood sugar, including as a nasal spray approved in 2019.
Key people
- Charles Kimball & John MurlinDiscovered glucagon (1923)
- William BromerSequenced it at Eli Lilly
- Roger UngerProposed glucagon’s role in diabetes
Timeline
- 1923
Glucagon discovered
- 1956
Amino acid sequence determined
- 1975
“Bihormonal” theory of diabetes
- 2019
Nasal glucagon approved
See every peptide on one history timeline.
Human evidence
Approved as an emergency treatment for severe hypoglycemia (including nasal and ready-to-use forms) and as a diagnostic aid in radiology.
Registration and enrollment are not proof of benefit; check study results directly.
Explore original publications and distinguish preclinical findings from controlled human evidence.
Safety and regulatory status
See every compound on the regulatory tracker.
FDA-approved for specific uses.
This profile is educational and does not provide treatment, dosing or sourcing guidance.
Sources
- PubMed literature search: Glucagon
- PubChem compound search: Glucagon
- DailyMed (FDA label search): Glucagon
- PubMed: Unger glucagon diabetes
- ClinicalTrials.gov search: Glucagon
Hernandez Gener, E. (2026, November 7). Glucagon: molecular data, research history and evidence. VALREXA Biosciences. https://valrexa.com/peptides/glucagon.html
APA style · Last reviewed November 7, 2026 · Our editorial standardsLast reviewed November 7, 2026. Trial and regulatory status can change; confirm in the linked registries. This profile is educational and is not medical advice, a treatment recommendation, or dosing or sourcing guidance. Report an error · Corrections policy