Peptide Basics
Glucagon: The Peptide Hormone That Raises Blood Sugar, How It Differs From Insulin, and the Medicines Made From It
Glucagon is a 29-amino-acid peptide hormone made by the alpha cells of the pancreas. It raises blood glucose by making the liver release and produce glucose, which makes it the counterpart of insulin. This page sets out what the glucagon molecule is, the precursor it shares with GLP-1, how it compares with insulin, the receptor it acts on, the glucagon medicines in FDA’s records and the investigational drugs that target its receptor. Every figure is taken from UniProt, PubChem, MeSH, PubMed or FDA’s own databases and labels.
What glucagon is
Glucagon is one of the peptide hormones. MeSH describes it as a 29-amino-acid pancreatic peptide derived from proglucagon, secreted by the alpha cells of the pancreas, that plays an important role in regulating blood glucose and ketone metabolism.
UniProt records that glucagon raises blood glucose by increasing gluconeogenesis, the making of new glucose, and decreasing glycolysis, its breakdown. It is the counterregulatory hormone of insulin: when insulin pushes blood glucose too low, glucagon brings it back up. Its release is stimulated by low blood glucose and inhibited by high blood glucose, by insulin and by somatostatin.
The human peptide reads HSQGTFTSDYSKYLDSRRAQDFVQWLMNT. PubChem gives it a molecular formula of C153H225N43O49S and a molecular weight of 3,482.7 (CID 16132283); FDA labels round the same figure to 3,483.
One precursor, cut two ways: proglucagon
Glucagon is cut from proglucagon, a precursor of 180 amino acids that also carries GLP-1. UniProt records that it is processed differently in each tissue. In the alpha cells of the pancreas, the enzyme PC2 releases glucagon. In the L cells of the gut, PC1 releases GLP-1, GLP-2, glicentin and oxyntomodulin instead. The pieces, by position in the precursor:
| Peptide | Positions | Amino acids | Note |
|---|---|---|---|
| Glicentin-related polypeptide | 21-50 | 30 | The front part of glicentin. |
| Glucagon | 53-81 | 29 | Cut out in the pancreas, in the alpha cells of the islets. |
| Oxyntomodulin | 53-89 | 37 | The glucagon sequence plus eight more amino acids; made in the gut. |
| Glicentin | 21-89 | 69 | The longest gut product; it contains the whole glucagon sequence. |
| GLP-1 (7-37) and (7-36) amide | 98-128 / 98-127 | 31 / 30 | The gut hormone behind semaglutide and the other GLP-1 medicines. |
| GLP-2 | 146-178 | 33 | A gut hormone that UniProt records as stimulating intestinal growth. |
That shared origin is why the two hormones are studied together. Our GLP-1 peptides page follows the gut branch and the medicines built on it.
Sources: UniProt P01275 (positions include the 20-residue signal peptide); MeSH D005934. Read 3 November 2026.
Glucagon vs insulin
Glucagon and insulin are made by neighbouring cells in the same pancreatic islets and work in opposite directions. As molecules they are quite different:
| Glucagon | Insulin | |
|---|---|---|
| Made by | Alpha (A) cells of the pancreatic islets | Beta cells of the pancreatic islets |
| Size and shape | One chain of 29 amino acids | Two chains, A (21) and B (30), joined by two disulfide bonds |
| Precursor | Proglucagon, 180 amino acids | Proinsulin, 110 amino acids including its signal |
| Effect on blood glucose, as UniProt records it | Raises it | Lowers it |
| How, in the liver | More gluconeogenesis, less glycolysis; glycogen broken down | Faster glycolysis and glycogen synthesis |
| Receptor | GCGR, a G protein-coupled receptor of 477 amino acids | INSR, the insulin receptor (precursor of 1,382 amino acids) |
Sources: UniProt P01275, P47871, P01308 and P06213. Read 3 November 2026.
The glucagon receptor, GCGR
Glucagon acts on the glucagon receptor, a G protein-coupled receptor of 477 amino acids that crosses the cell membrane seven times. UniProt records that it sets the rate at which the liver produces glucose, by promoting the breakdown of stored glycogen and gluconeogenesis, and that it plays an important role in the body’s responses to fasting. When glucagon binds, the receptor couples to Gs proteins, which activate adenylate cyclase and raise cyclic AMP inside the cell.
The structure of the human receptor bound to its G proteins was published in Science in 2020. The same receptor is the third target of the investigational triple agonist retatrutide, described further down.
Sources: UniProt P47871; PubMed 32193322 (Qiao and colleagues, Science 2020). Read 3 November 2026.
Glucagon as a medicine: what FDA’s records show
Glucagon has been an approved medicine in the United States for more than sixty years. Its labels name two uses: treating severe hypoglycemia in people with diabetes, and, given into a vein or muscle, briefly stopping movement of the stomach and intestines so that radiology images are clearer. Every glucagon label we read describes it as identical to human glucagon; the Gvoke label and two injection labels add that it is synthetic, made by solid-phase peptide synthesis, and identical to human glucagon. The approvals in Drugs@FDA, by year of first approval:
| Product | Application | Approved | What the record and label show |
|---|---|---|---|
| Glucagon (Eli Lilly) | NDA 012122 | 1960 | The earliest glucagon record in Drugs@FDA; discontinued. |
| GlucaGen (Novo Nordisk) | NDA 020918 | 1998 | Glucagon hydrochloride; discontinued. |
| Glucagon for Injection (Fresenius Kabi) | NDA 201849 | 2015 | Lyophilised powder; labelled only as a diagnostic aid in radiology, not for emergency use. |
| Baqsimi | NDA 210134 | 2019 | Nasal powder; labelled for severe hypoglycemia in people with diabetes aged 1 year and older. |
| Gvoke | NDA 212097 | 2019 | Ready-to-use solution; severe hypoglycemia from age 2; the VialDx form is a radiology diagnostic aid. |
| Zegalogue (dasiglucagon) | NDA 214231 | 2021 | A 29-amino-acid glucagon analogue; listed as discontinued. |
| Generic glucagon | ANDAs | 2020-2025 | Four abbreviated approvals: Amphastar 2020, Mylan 2024, Lupin and Cipla 2025. |
The traditional kits hold glucagon as a freeze-dried powder that is mixed with a liquid just before use. Our page on lyophilized peptides uses a glucagon label to show how little of such a vial is the peptide itself.
Sources: Drugs@FDA via openFDA (original approval dates and marketing status), and the current U.S. labels for Baqsimi, Gvoke, Zegalogue and two glucagon injection products. Read 3 November 2026. Doses are not reproduced here.
Investigational drugs that target the glucagon receptor
A newer group of peptides acts on the glucagon receptor together with the GLP-1 receptor, and in one case the GIP receptor as well. None has an approval in FDA’s records: a search of Drugs@FDA on 3 November 2026 returned no record for any of the three.
| Compound | Receptors | Approval record |
|---|---|---|
| Retatrutide | GIP, GLP-1 and glucagon receptors | No Drugs@FDA record |
| Survodutide | GLP-1 and glucagon receptors | No Drugs@FDA record |
| Mazdutide | GLP-1 and glucagon receptors | No Drugs@FDA record; approved in China in June 2025, per its developer |
These compounds are also sold as research peptides. A product labelled research use only is labelled not for human use; our page on what research peptides are explains that label, and each guide sets out one compound’s identity, research history and regulatory record.
Sources: PubChem CID 171378821 (survodutide) and 167312357 (mazdutide); openFDA searches of 3 November 2026. Read 3 November 2026.
Medibact does not manufacture or sell peptides. We supply USP-grade bacteriostatic water, made in the USA, for research use only, and publish reference material like this page.
Where this sits in the rest of the reference
FAQ
What is glucagon?
Glucagon is a peptide hormone of 29 amino acids made by the alpha cells of the pancreatic islets. MeSH, the U.S. National Library of Medicine's subject index, describes it as a pancreatic peptide derived from proglucagon that regulates blood glucose and ketone metabolism. UniProt records that it raises blood glucose by increasing gluconeogenesis in the liver and decreasing glycolysis, and calls it the counterregulatory hormone of insulin.
Is glucagon a peptide or a protein?
A peptide. Glucagon is a single chain of 29 amino acids, HSQGTFTSDYSKYLDSRRAQDFVQWLMNT, with a molecular weight of about 3,483. FDA labels describe it as a single-chain polypeptide of 29 amino acid residues. It is cut from a larger precursor, proglucagon, which has 180 amino acids.
What is the difference between glucagon and insulin?
They come from neighbouring cells in the same pancreatic islets and push blood glucose in opposite directions. Glucagon, from alpha cells, is one chain of 29 amino acids that raises blood glucose; insulin, from beta cells, is two chains of 21 and 30 amino acids joined by disulfide bonds that lowers it. UniProt records that glucagon release is stimulated by low blood glucose and inhibited by high blood glucose, insulin and somatostatin.
What does glucagon do in the liver?
It binds the glucagon receptor, GCGR, which UniProt records as regulating the rate at which the liver makes glucose. The receptor promotes the breakdown of stored glycogen and gluconeogenesis, the making of new glucose, and plays an important role in the body's responses to fasting. It signals through Gs proteins and raises cyclic AMP inside the cell.
How are glucagon and GLP-1 related?
They come from the same gene. Proglucagon is processed differently in each tissue: in the pancreas the enzyme PC2 cuts out glucagon, while in the L cells of the gut PC1 releases GLP-1, GLP-2, glicentin and oxyntomodulin instead. GLP-1 lowers glucagon levels, which is one reason the two are studied together. Our GLP-1 peptides page covers that branch.
What is glucagon used for as a medicine?
In the United States, glucagon products are labelled for two uses: treating severe hypoglycemia in people with diabetes, and as a diagnostic aid that temporarily stops movement of the gut during radiology examinations. Drugs@FDA's earliest glucagon record is Eli Lilly's NDA 012122 from 1960. Current forms include a nasal powder (Baqsimi), a ready-to-use solution (Gvoke) and generic injection kits. Every glucagon label we read describes it as identical to human glucagon, and the Gvoke label and two injection labels say it is synthetic.
What is dasiglucagon?
Dasiglucagon is a glucagon analogue: its U.S. label describes it as a peptide of 29 amino acids, the same length as glucagon, with its own sequence. FDA approved it as Zegalogue on 22 March 2021 for severe hypoglycemia in people with diabetes aged 6 and older; Drugs@FDA now lists it as discontinued. PubChem gives its formula as C152H222N38O50 and its molecular weight as 3,381.6.
Which new drugs target the glucagon receptor?
Several investigational multi-agonists add the glucagon receptor to GLP-1. Retatrutide acts on GIP, GLP-1 and glucagon receptors; survodutide and mazdutide act on GLP-1 and glucagon receptors. None had a Drugs@FDA record when searched on 3 November 2026; mazdutide was approved in China in June 2025, according to its developer.
Is this medical advice?
No. This page explains what glucagon is, from public scientific and regulatory sources. It gives no dose, schedule or recommendation; anyone with diabetes should follow the instructions of their own clinician and product label. Peptides sold for research are labelled research use only, not for human use. Medibact supplies USP-grade bacteriostatic water, made in the USA, and is not affiliated with any manufacturer of the products named here.
References: UniProt P01275, P47871, P01308, P06213; MeSH D005934; PubChem CID 16132283, 126961379, 171378821, 167312357; PubMed 32193322; Drugs@FDA via openFDA and the current U.S. labels named above. Read 3 November 2026.
Educational use only — not medical advice. This guide summarizes information reported in published research and community practice for educational purposes. It is not medical advice and not a recommendation to use any compound. Any doses, schedules, or combinations shown are examples of what has been reported, not instructions for you. Many peptides described here are research compounds that are not FDA-approved for the uses discussed and may be investigational or restricted. Effects, risks, and legal status vary; individual needs and results vary. Consult a qualified, licensed healthcare professional before making any decision. Do not use this content to diagnose, treat, or dose yourself.