Glucagon
A naturally occurring peptide hormone that raises blood sugar, FDA-approved as emergency treatment for severe hypoglycemia.
What is Glucagon?
Glucagon is a 29-amino acid peptide hormone produced by alpha cells of the pancreas. It is the primary counter-regulatory hormone to insulin, raising blood glucose by stimulating hepatic glycogenolysis and gluconeogenesis. Synthetic glucagon is FDA-approved for emergency treatment of severe hypoglycemia and as a diagnostic aid for GI imaging.
What Glucagon Is Investigated For
Glucagon has two longstanding FDA-approved use cases — emergency treatment of severe hypoglycemia in insulin-treated diabetic patients and diagnostic smooth-muscle relaxation for GI imaging procedures — plus an emerging role as a component of dual and triple receptor agonists for chronic obesity (mazdutide, survodutide, retatrutide). The strongest evidence is for the rescue indication: decades of clinical use since FDA approval in 1960, with modernized formulations including Baqsimi intranasal powder (2019) and Gvoke HypoPen pre-mixed auto-injector (2019) that dramatically improved lay-caregiver usability. The glucagon receptor mechanism — cAMP-mediated hepatic glycogenolysis and gluconeogenesis — is one of the best-characterized hormone pathways in metabolism. Mazdutide, the first GCGR/GLP-1R dual agonist to clear Phase 3 (2026 Nature placebo and dulaglutide head-to-head trials in Chinese T2D, plus a Phase 2 in non-diabetic obesity at 9 mg) is now the most concrete clinical instantiation of controlled glucagon receptor agonism, supplying weight reductions of roughly 6–7 kg vs. placebo in network meta-analyses of glucagon-receptor-active agents. The honest caveats: rescue glucagon depends on intact hepatic glycogen stores, failing in prolonged starvation, severe liver disease, chronic alcohol use, or adrenal insufficiency (where IV dextrose is the necessary intervention); the weight-loss attributed to 'glucagon' comes from dual/triple agonists rather than native single-dose use; and Western obesity-drug programs using chronic controlled glucagon agonism (survodutide, retatrutide) are still in Phase 3, with their long-term safety separately characterized.
History & Discovery
Glucagon was first identified in 1923 by Charles Kimball and John Murlin at the University of Rochester, who noticed a hyperglycemic contaminant in pancreatic extracts being studied for insulin's hypoglycemic effects. They named it 'glucagon' for 'glucose agonist,' and characterized it as the principal counter-regulatory hormone opposing insulin. The amino acid sequence was determined by Bromer and colleagues in 1957, and crystalline glucagon was isolated and approved by the FDA in 1960 for emergency treatment of severe hypoglycemia. For decades, the only formulation was a reconstituted lyophilized injection — effective but cumbersome under emergency conditions, where caregivers had to mix the powder, draw up the solution, and inject within minutes of severe hypoglycemia. The 2019 approvals of Baqsimi (intranasal glucagon, Lilly) and Gvoke HypoPen (pre-mixed liquid auto-injector, Xeris) modernized the rescue paradigm, removing the reconstitution step and dramatically improving usability for the lay caregivers most likely to administer the dose. In parallel, controlled glucagon receptor agonism re-emerged as a therapeutic concept in the 2010s and 2020s through the dual GLP-1/glucagon and triple GLP-1/GIP/glucagon agonists (mazdutide, survodutide, retatrutide), repurposing the hormone's energy-expenditure and hepatic-fat-oxidation effects for chronic obesity treatment.
How It Works
Glucagon is insulin's opposite. When blood sugar drops dangerously low, glucagon tells the liver to release its stored sugar (glycogen) into the bloodstream, rapidly raising blood sugar levels to safe ranges.
Glucagon binds to the glucagon receptor (GCGR), a Class B GPCR on hepatocytes, activating adenylyl cyclase and increasing cAMP. This activates PKA, which phosphorylates glycogen phosphorylase (stimulating glycogenolysis) and inhibits glycogen synthase. It also activates gluconeogenic enzymes (PEPCK, G6Pase) for de novo glucose production. In adipose tissue, glucagon promotes lipolysis. The glucagon receptor is also a target in newer obesity drugs (retatrutide) where controlled glucagon agonism increases energy expenditure.
Evidence Snapshot
Human Clinical Evidence
Extensive. Decades of clinical use as emergency medication. Multiple FDA-approved formulations.
Animal / Preclinical
Comprehensive. Glucagon biology is fundamental to metabolic physiology.
Mechanistic Rationale
Very strong. Glucagon receptor signaling is one of the best-characterized hormone pathways.
Research Gaps & Open Questions
What the current literature has not yet settled about Glucagon:
- 01Stable, ready-to-use formulations have largely solved the practical usability problem, but cost and access barriers remain — many at-risk patients still do not carry a current emergency device.
- 02Whether intranasal Baqsimi and injectable formulations are clinically equivalent in real-world emergencies (where caregiver familiarity dominates outcomes) is incompletely characterized.
- 03Optimal use of glucagon in patients on GLP-1 agonists, who may have altered counter-regulatory responses, is an emerging area of study. Recent T1D crossover work also shows that the glucagonotropic effect of GIP — a potential adjunct to insulin-induced hypoglycemia rescue — is blunted during hypoglycemia itself, complicating GIP-based rescue paradigms.
- 04Long-term controlled glucagon receptor agonism via the dual and triple agonists (mazdutide, survodutide, retatrutide) has different safety considerations from single-dose rescue use, and these are being characterized through dedicated Phase 3 programs.
- 05Pediatric mini-dose glucagon (subcutaneous low-dose for milder hypoglycemia in young children) is used off-label but lacks dedicated approved formulations.
- 06Whether routine glucagon prescribing for at-risk patients meaningfully reduces severe hypoglycemia hospitalization rates at the population level is not well quantified.
Forms & Administration
IM/SC injection (GlucaGen 1mg kit), nasal powder (Baqsimi 3mg), auto-injector (Gvoke 0.5-1mg). Emergency kits designed for non-medical personnel use. All injectable peptides should only be administered under the guidance of a qualified healthcare provider. Never self-administer without clinician oversight.
Dosing & Protocols
The ranges below reflect protocols commonly discussed in the literature and by clinicians — not a prescription. Actual dosing for any individual should be determined by a qualified healthcare provider who knows the patient.
Typical Range
For severe hypoglycemia rescue, the FDA-labeled doses are: 1 mg subcutaneous or intramuscular injection (GlucaGen, Lilly Glucagon Emergency Kit) for adults and pediatric patients ≥25 kg, with 0.5 mg for pediatric patients <25 kg or younger than 6 years; 3 mg intranasal powder (Baqsimi) as a single fixed dose for adults and pediatric patients ≥4 years; or 0.5–1 mg pre-mixed liquid auto-injector (Gvoke HypoPen) by adult or weight band. For diagnostic GI use during imaging procedures, doses range from 0.25 to 2 mg IV depending on the procedure and target relaxation.
Frequency
Glucagon for hypoglycemia rescue is single-dose; if the patient does not respond within 15 minutes, the labeled instruction is to seek emergency medical care (a second dose can be given but is rarely sufficient if the first failed and IV dextrose is the appropriate next step). Diagnostic use is single-dose during the relevant imaging window.
Timing Considerations
No specific timing requirements: can be administered at any time of day, with or without food, and is not tied to exercise timing. Consistency matters more than the specific clock — dose at roughly the same time each day (or same day each week, for weekly protocols) to keep exposure steady.
Protocol Notes
All emergency glucagon products are designed for use by lay caregivers (family members, school personnel, coworkers) of insulin-treated diabetic patients, typically when the patient is unconscious, seizing, or otherwise unable to take oral carbohydrate. The rescue product belongs in the home, school bag, gym bag, and workplace of any patient at risk of severe hypoglycemia, and family members should be trained on its administration in advance. After rescue, the patient must be turned on their side (vomiting is common as glucagon raises blood sugar) and given oral carbohydrate as soon as they can swallow safely, then evaluated by their diabetes care team to identify what triggered the episode. Glucagon is ineffective in patients with depleted hepatic glycogen (prolonged starvation, severe hepatic disease, chronic alcoholism, adrenal insufficiency), where the rescue mechanism — mobilizing stored glycogen — has nothing to mobilize.
Glucagon dosing should follow the specific product labeling and individual prescriber guidance. Caregiver training on the device-specific administration steps before an emergency arises is essential.
Timeline of Effects
Onset
Plasma glucose typically begins to rise within 5–10 minutes of injection, with the patient regaining consciousness within 10–15 minutes if the cause is hypoglycemia and hepatic glycogen is intact. Intranasal Baqsimi achieves comparable timing despite the alternate route. Diagnostic GI relaxation typically occurs within 1–3 minutes of IV administration.
Peak Effect
Peak plasma glucose elevation occurs at approximately 15–30 minutes post-injection, with magnitude depending on the patient's hepatic glycogen reserves. The rescue effect is by design transient — a bridge to the point at which the patient can swallow oral carbohydrate or receive IV dextrose.
After Discontinuation
Glucagon's plasma half-life is approximately 8–18 minutes, and its glycemic effect resolves within 60–90 minutes. Because glucagon does not address the underlying cause of hypoglycemia (insulin overdose, missed meal, exercise mismatch), rebound hypoglycemia is common within 1–2 hours of rescue if oral carbohydrate is not consumed. There is no concept of long-term withdrawal because rescue glucagon is single-dose acute therapy.
Common Questions
Who Glucagon Is NOT For
- •Pheochromocytoma — glucagon can stimulate catecholamine release from the tumor, precipitating hypertensive crisis.
- •Insulinoma — glucagon may initially raise blood glucose but then trigger a paradoxical insulin surge from the tumor, worsening hypoglycemia.
- •Known hypersensitivity to glucagon or to formulation excipients — anaphylactic reactions have been reported, though they are rare.
- •Glucagonoma — additional glucagon administration in a patient already producing pathological excess is contraindicated.
- •Patients with depleted hepatic glycogen are not contraindicated per se, but glucagon will be ineffective — IV dextrose is the appropriate intervention. This includes prolonged starvation, severe hepatic disease, chronic alcohol use disorder, and adrenal insufficiency.
- •For diagnostic use, conditions where smooth muscle relaxation is undesirable (severe ileus, mechanical obstruction needing surgical evaluation) warrant caution.
Drug & Supplement Interactions
The most clinically important interaction is with anticoagulants — glucagon can potentiate the anticoagulant effect of warfarin, an interaction relevant primarily in the rare case of repeated diagnostic glucagon administration rather than single-dose hypoglycemia rescue. Beta-blockers can blunt the catecholamine response to hypoglycemia and theoretically prolong the time to recovery after glucagon rescue, though this rarely changes clinical management of an acute episode. Indomethacin can interfere with glucagon's hyperglycemic effect by blocking hepatic glucose output, potentially reducing rescue efficacy. Glucagon increases hepatic glucose output and may transiently affect glycemic control in patients on insulin or oral hypoglycemics, though this is the intended effect in the rescue context. There are no clinically significant interactions for the intranasal Baqsimi formulation beyond those that apply to glucagon generically. The investigational and emerging dual/triple agonists incorporating glucagon receptor agonism have their own distinct interaction profiles characterized in their respective trial programs.
Safety Profile
Common Side Effects
Cautions
- • Not effective in patients with depleted liver glycogen (starvation, adrenal insufficiency)
- • May cause rebound hypoglycemia
- • Contraindicated in pheochromocytoma and insulinoma
What We Don't Know
Well-characterized safety profile as a natural hormone with decades of clinical use.
Legal Status
United States
Glucagon is FDA-approved as multiple branded products including GlucaGen (Novo Nordisk, reconstituted injection), Lilly Glucagon Emergency Kit (reconstituted injection), Baqsimi (Lilly, intranasal powder, 2019), and Gvoke HypoPen / Gvoke PFS (Xeris, pre-mixed liquid auto-injector and pre-filled syringe, 2019). All formulations are prescription-only. Generic injectable glucagon also exists. The various dual and triple receptor agonists incorporating glucagon receptor agonism (mazdutide approved in China, survodutide and retatrutide investigational) are separate molecules subject to their own regulatory status.
International
Native glucagon products including GlucaGen are approved by the EMA, UK MHRA, Health Canada, Australia's TGA, and most other major regulators worldwide, where it is similarly stocked as emergency rescue medication for insulin-treated diabetes patients. Baqsimi and Gvoke have approvals in many of the same jurisdictions, though availability and reimbursement vary.
Sports & Competition
Native glucagon as an FDA-approved peptide hormone falls under WADA's S2 category (peptide hormones, growth factors, related substances and mimetics) and is technically prohibited at all times under the WADA code, though it is used in legitimate medical emergencies. Therapeutic Use Exemptions cover diabetic athletes who require glucagon as rescue medication. Routine documentation of insulin-treated diabetes is sufficient to establish medical necessity.
Regulatory status changes over time. Verify current local rules with a qualified professional.
Myths & Misconceptions
Myth
Glucagon causes weight loss when used regularly.
Reality
Native single-dose glucagon for hypoglycemia rescue does not produce sustained weight loss — its effect is acute hyperglycemia followed by return to baseline. The weight-loss effects attributed to 'glucagon' come from the dual and triple agonists (mazdutide, survodutide, retatrutide), where chronic controlled glucagon receptor agonism combined with GLP-1 agonism increases energy expenditure and promotes hepatic fat oxidation. Native glucagon as a standalone weight-loss agent has not been clinically validated.
Myth
Glucagon and insulin are opposites, so one cancels the other.
Reality
They have opposing physiologic effects on blood glucose, but they act on different tissues through different receptors, and their dynamics are not symmetric. Insulin's effect lasts hours; glucagon's lasts under 90 minutes. Glucagon rescues acute hypoglycemia by mobilizing hepatic glycogen, but it does not 'reverse' insulin's effect — it temporarily elevates blood glucose while insulin continues to act. This is why oral carbohydrate or IV dextrose remains the definitive treatment after glucagon rescue.
Myth
Glucagon rescue always works for severe hypoglycemia.
Reality
Glucagon depends on hepatic glycogen stores to raise blood glucose. In patients with depleted glycogen — prolonged starvation, severe alcohol use, advanced liver disease, adrenal insufficiency — glucagon can fail entirely. In these scenarios IV dextrose is the necessary intervention, and emergency services should be summoned without delay.
Myth
The intranasal Baqsimi version is less effective than the injection because it is not delivered into the bloodstream directly.
Reality
Bioavailability through the nasal mucosa is sufficient to produce comparable rescue glucose elevation, and head-to-head usability studies have favored the intranasal formulation in lay-caregiver scenarios where the injection's reconstitution and injection steps add critical seconds and error potential. Both routes are clinically valid; the choice depends on patient and caregiver preference and access.
Published Research
38 studiesThe Glucagonotropic Effect of GIP Is Negated During Insulin-Induced Hypoglycemia in Type 1 Diabetes
Mazdutide 9 mg in Chinese adults with a body mass index ≥30 kg/m² but without diabetes: A phase 2 randomized controlled trial
Comparative Efficacy and Safety of Glucagon Receptor Agonists on Metabolic Outcomes: A Network Meta-Analysis
Mazdutide versus dulaglutide in Chinese adults with type 2 diabetes
2026 Nature Phase 3 head-to-head against dulaglutide demonstrating mazdutide's GCGR/GLP-1R dual agonism produces incremental weight and metabolic benefit beyond pure GLP-1 agonism in T2D — the seminal comparator establishing differentiation of glucagon-component pharmacology.
Mazdutide versus placebo in Chinese adults with type 2 diabetes
2026 Nature Phase 3 trial establishing the dual GCGR/GLP-1R agonist mazdutide as superior to placebo for glycemic control and weight in Chinese T2D — the first published Nature-tier evidence base for controlled glucagon receptor agonism in chronic metabolic disease.
Baseline characteristics in the SYNCHRONIZE™-2 randomized phase 3 trial of survodutide, a glucagon receptor/GLP-1 receptor dual agonist, for obesity in people with type 2 diabetes
Survodutide for treatment of obesity: Baseline characteristics of participants in a randomized, double-blind, placebo-controlled, phase 3 trial (SYNCHRONIZE™-1)
Preclinical evaluation and first-in-human phase 1 trial of AZD0186, a novel, oral small molecule glucagon-like peptide-1 receptor agonist
Using glucagon receptor antagonism to evaluate the physiological effects of extrapancreatic glucagon in totally pancreatectomised individuals: a randomised controlled trial
Counterregulatory response to hypoglycemia during a hypoglycemic clamp in people with type 2 diabetes treated with tirzepatide
Effect of Almond Milk Versus Cow Milk on Postprandial Glycemia, Lipidemia, and Gastrointestinal Hormones in Patients with Overweight or Obesity and Type 2 Diabetes: A Randomized Controlled Clinical Trial
Dapagliflozin's impact on hormonal regulation and ketogenesis in type 1 diabetes: a randomised controlled crossover trial
Exenatide and glucagon co-infusion increases myocardial glucose uptake and improves markers of diastolic dysfunction in adults with type 2 diabetes
Baseline glucagon impacts glucose-lowering effects of acarbose but not metformin: A sub-analysis of MARCH study
A Randomized Controlled, Double-Masked, Crossover Study of a GPR119 Agonist on Glucagon Counterregulation During Hypoglycemia in Type 1 Diabetes
Testing the carbohydrate-insulin model: Short-term metabolic responses to consumption of meals with varying glycemic index in healthy adults
Efficacy and safety of red ginseng extract powder (KGC05pg) in achieving glycemic control in prediabetic Korean adults: A 12-week, single-center, randomized, double-blind, parallel-group, placebo-controlled study
Regulation of proglucagon derived peptides by carbohydrate and protein ingestion in young healthy males-A randomized, double-blind, cross-over trial
Effect of Barley on Postprandial Blood Glucose Response and Appetite in Healthy Individuals: A Randomized, Double-Blind, Placebo-Controlled Trial
Enteropancreatic hormone changes in caloric-restricted diet interventions associate with post-intervention weight maintenance
Effect of pemvidutide, a GLP-1/glucagon dual receptor agonist, on MASLD: A randomized, double-blind, placebo-controlled study
Effects of Tirzepatide vs Semaglutide on β-Cell Function, Insulin Sensitivity, and Glucose Control During a Meal Test
Combination SGLT2 Inhibitor and Glucagon Receptor Antagonist Therapy in Type 1 Diabetes: A Randomized Clinical Trial
Dual glucagon-like peptide-1 and glucagon receptor agonism reduces energy intake in type 2 diabetes with obesity
Adaptive infusion of a glucagon-like peptide-1/glucagon receptor co-agonist G3215, in adults with overweight or obesity: Results from a phase 1 randomized clinical trial
Cotadutide promotes glycogenolysis in people with overweight or obesity diagnosed with type 2 diabetes
Orforglipron (LY3502970), a novel, oral non-peptide glucagon-like peptide-1 receptor agonist: A Phase 1b, multicentre, blinded, placebo-controlled, randomized, multiple-ascending-dose study in people with type 2 diabetes
Weight Loss-Independent Effect of Liraglutide on Insulin Sensitivity in Individuals With Obesity and Prediabetes
Double-Blind Multicenter Randomized Clinical Trial Comparing Glucagon vs Placebo in the Resolution of Alimentary Esophageal Impaction
No effect of multi-strain probiotic supplementation on metabolic and inflammatory markers and newborn body composition in pregnant women with obesity: Results from a randomized, double-blind placebo-controlled study
Effect of Isocaloric Meals on Postprandial Glycemic and Metabolic Markers in Type 1 Diabetes-A Randomized Crossover Trial
Weight loss maintenance with exercise and liraglutide improves glucose tolerance, glucagon response, and beta cell function
Glucagon-like peptide-1/glucagon receptor agonism associates with reduced metabolic adaptation and higher fat oxidation: A randomized trial
New Developments in Glucagon Treatment for Hypoglycemia
Nutraceutical Eriocitrin (Eriomin) Reduces Hyperglycemia by Increasing Glucagon-Like Peptide 1 and Downregulates Systemic Inflammation: A Crossover-Randomized Clinical Trial
Hypoglycemia following the use of glucagon-like peptide-1 receptor agonists: a real-world analysis of post-marketing surveillance data
Glucagon: Its evolving role in the management of hypoglycemia
Glucagon for hypoglycemic episodes in insulin-treated diabetic patients: a systematic review and meta-analysis with a comparison of glucagon with dextrose and of different glucagon formulations
Quick Facts
- Class
- Peptide Hormone
- Tier
- B
- Evidence
- Strong
- Safety
- Well-Studied
- Updated
- May 2026
- Citations
- 38PubMed
Also known as
Tags
Related Goals
Evidence Score
Clinical Trials
View Clinical TrialsLinks to ClinicalTrials.gov for reference. Listing does not imply endorsement.