Pharmacology · Drugs that raise blood glucose
Glucagon !
The emergency treatment for severe hypoglycemia when the person cannot eat: it releases the glucose stored in the liver.
Updated 2026-11-01
The figure shows human glucagon bound to the human glucagon receptor coupled to its Gs protein. The nanobody used to stabilize the complex is not part of the receptor.
Mechanism of action
Glucagon binds its Gs-coupled receptor on liver cells. Adenylyl cyclase makes cAMP, protein kinase A is activated and phosphorylates the enzymes of glycogen metabolism: glycogen phosphorylase is switched on and glycogen synthase off, so glucose is released within minutes. Gluconeogenesis also increases. In the gut, glucagon relaxes smooth muscle, which is used during radiology.
- Binds the glucagon receptor on liver cells (Gs, cAMP)
- Protein kinase A switches glycogen breakdown on
- The liver releases glucose and makes new glucose
- Blood glucose rises within minutes if glycogen is stored
Pharmacokinetics
- Absorption
- Given by injection (subcutaneous, intramuscular or intravenous); nasal powder forms also exist.
- Metabolism
- Broken down quickly in the liver, kidney and plasma.
- Onset and duration
- Glucose rises within minutes; the effect is short, so food follows once the person can swallow.
Indications
- Severe hypoglycemia in people with diabetes, when they cannot take sugar by mouth
- Diagnostic aid in radiology, to briefly relax the stomach and bowel
Adverse effects
Common
- Nausea and vomiting
- Headache
- Fast heart rate, transient rise in blood pressure
- Injection-site reactions
Contraindications
- Pheochromocytoma
- Insulinoma
- Hypersensitivity to glucagon
- Glucagonoma, when used as a diagnostic aid
Key interactions
- Beta-blockers
- Transient rise in pulse and blood pressure.
- Indomethacin
- Glucagon may fail to raise glucose or may even cause hypoglycemia.
- Warfarin
- Its anticoagulant effect may increase.
- Anticholinergic drugs
- Not combined for gut relaxation during radiology: more gut side effects.
What is monitored
- Blood glucose after the dose and until the person eats
- Level of consciousness and airway
- Pulse and blood pressure
Administration and safety
- Kits with powder are mixed with the supplied diluent just before use and given at once.
- Family members and caregivers of people on insulin are taught to use it.
- After the injection the person is turned onto their side, because vomiting is common.
- If there is IV access, intravenous glucose is the first choice in hospital.
Nursing care
- Check glucose before and repeatedly after the dose.
- Protect the airway and place in recovery position.
- Give oral carbohydrate once the person can swallow, to refill glycogen and prevent relapse.
- Look for the cause (insulin or sulfonylurea excess, missed meal, alcohol).
Pregnancy and breastfeeding
Decades of use in pregnancy have not shown a clear risk; severe hypoglycemia itself is the bigger danger.
Test yourself
Think of the answer, then tap the question to see it.
Why may glucagon fail in a patient with adrenal insufficiency or after prolonged starvation?
It works by releasing liver glycogen; these patients have little glycogen, so intravenous glucose is needed.
Why is glucagon contraindicated in pheochromocytoma?
It can make the tumor release catecholamines and cause a sudden, severe rise in blood pressure.
What should happen once a patient wakes up after glucagon?
They are given carbohydrate by mouth as soon as they can swallow, because the effect is short and glycogen must be refilled.
Which enzyme does protein kinase A switch on in the liver after glucagon?
Glycogen phosphorylase (through phosphorylase kinase), while glycogen synthase is switched off.
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Glucagon Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); DailyMed - GLUCAGON kit (DailyMed (U.S. National Library of Medicine), 2026); Cryo-EM structure of the human glucagon receptor in complex with Gs (RCSB Protein Data Bank, 2020); eEML - Electronic Essential Medicines List (World Health Organization, 2025).
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Representative model, for educational purposes only.