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Blood test

Glucagon test

Glucagon test: what it measures, why a doctor orders it, how to prepare, and what a high or low result can mean - with private and NHS access routes in the UK.

Key facts

At a glance

  • What it measures: how your growth hormone and cortisol respond to an injection of glucagon - a combined test of pituitary reserve.

  • Why it is ordered: when growth hormone or ACTH deficiency is suspected but the insulin stress test is unsuitable or unavailable.

  • A supervised fasted morning in a day unit - glucagon is injected and blood is sampled over three to four hours; nausea is the common side effect.

  • Reference ranges: peak growth hormone and cortisol responses are judged against protocol-specific thresholds. Every laboratory publishes its own interval, so the range printed on your report is the one that applies to you.

  • A raised result or adequate peaks exclude significant deficiency of the axes tested. A low result or blunted responses support pituitary hormone deficiency and guide replacement therapy.

  • Results typically take a few days to two weeks, because the sample is analysed in batches at a specialist laboratory.

The full picture

What this test tells you, and how to get it

The glucagon test measures how your growth hormone and cortisol respond to an injection of glucagon - a combined test of pituitary reserve. Doctors most often request it when growth hormone or ACTH deficiency is suspected but the insulin stress test is unsuitable or unavailable. A supervised fasted morning in a day unit - glucagon is injected and blood is sampled over three to four hours; nausea is the common side effect. Peak growth hormone and cortisol responses are judged against protocol-specific thresholds, and reference intervals genuinely differ between laboratories, so no single number should be treated as a universal cut-off - your result is always read against the range printed on your own report. Broadly, a raised result or adequate peaks exclude significant deficiency of the axes tested, while a low result or blunted responses support pituitary hormone deficiency and guide replacement therapy, and either finding is interpreted alongside your symptoms, medication and other results rather than in isolation. Results typically take a few days to two weeks, because the sample is analysed in batches at a specialist laboratory.

In the UK there are two routes to this test. Your NHS GP can arrange it free of charge when it is clinically indicated, though getting the appointment, the blood draw and the follow-up discussion can add days to weeks depending on local demand. Privately, the glucagon test can usually be booked within days - through a private GP, a walk-in phlebotomy clinic or a self-request home-testing service - through endocrine investigation units. A private result still deserves a clinician's interpretation: an isolated number without context is where most confusion about blood tests begins.

A quiet reminder

This guide is for information, not medical advice.

Your own clinician knows your history and can tell you which parts apply to you. Reference ranges vary between laboratories - always read your result against the interval printed on your own report. Next review of this page: 2027-09-27.

Frequently asked

Common questions about Glucagon test.

Quick, plain-English answers to what people ask us most.

  • What is a glucagon test?

    Glucagon is a hormone made in the pancreas that helps raise blood sugar levels, and this blood test measures its level to help investigate certain rare hormone or pancreatic conditions. It's a specialist test rather than a routine diabetes screening tool.

  • Why would a doctor order a glucagon test?

    It's used to investigate suspected rare tumours of the pancreas, such as glucagonoma, particularly when someone has unusual symptoms like a specific skin rash alongside diabetes or weight loss. It may also be used in the investigation of unexplained low or high blood sugar.

  • Do I need to prepare for it?

    You may need to fast beforehand, and your doctor will advise on any medications that should be paused, as this is a specialist test where preparation matters for accuracy.

  • What happens during the test?

    It's usually a blood sample taken from a vein in your arm, sometimes as part of a more detailed hormone or pancreatic function assessment depending on what's being investigated.

  • Does it hurt or have risks?

    Only the usual minor discomfort of a blood draw, with no significant risks.

  • How long do results take?

    As a specialist hormone test, results typically take longer than routine bloods, often one to two weeks.

  • What do abnormal results mean, and what happens next?

    Significantly raised glucagon levels can point towards a rare pancreatic tumour and would usually prompt further imaging investigation. Your doctor will explain what the result means in the context of your symptoms and discuss any further tests needed.

  • How much does it cost privately, and is it available on the NHS?

    Glucagon testing for suspected rare conditions is available on the NHS through specialist endocrine or gastroenterology services. Private specialist assessment can be arranged, cost varying by provider.

  • Is it accurate and reliable?

    The test itself is reliable when performed and interpreted by specialists familiar with these rare conditions, though results need careful clinical context given how uncommon significant abnormalities are. Your doctor will guide you through what any result means.

  • How do I book it privately, and how quickly can I be seen?

    You can book a private specialist consultation to discuss your symptoms and whether this test is appropriate, usually within one to two weeks.