Health condition
Reactive hypoglycaemia vs insulinoma
Shakiness and sweating a few hours after meals is usually reactive (post-prandial) hypoglycaemia or adrenaline surges without true low glucose - distinguishing this benign pattern from the rare but serious insulinoma rests on timing and documented glucose values.
Why trust this guide
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Editorial team
Written by our editorial team from the UK sources listed on each page.
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Sourced from guidance
Checked against current NHS and UK specialist society guidance at the time of review.
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Current for 2026
Reviewed on 2026-09-27 with the next review scheduled for 2027-09-27.
Key facts
The essentials at a glance.
The symptoms to recognise, when to seek help, which specialist to see, and what treatment usually involves.
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Timing is the key discriminator: reactive symptoms follow meals by 2-4 hours; insulinoma classically strikes when fasting or after exercise
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Documentation beats description: a glucose measurement during symptoms (or a monitored fast) anchors the diagnosis
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Many with post-meal symptoms never have glucose below 3.0 mmol/L - the picture is often adrenaline response, not true hypoglycaemia
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Insulinoma red flags: fasting or early-morning episodes, neuroglycopenia (confusion, odd behaviour, seizures), symptoms relieved by food, weight gain
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First-line management of reactive symptoms is dietary: smaller mixed meals, lower glycaemic load, protein with carbohydrate
Understanding the condition
What it is and what happens next.
What causes it, how it is diagnosed, and the treatment routes available in the UK.
What it is and how it feels
After a large refined-carbohydrate meal, insulin can overshoot, dipping glucose as the meal's absorption tails off - the familiar 11am or mid-afternoon tremor, sweat and irritability. It is common, benign and dietary. Insulinoma is the opposite pattern: the tumour secretes regardless of food, so trouble comes when no food is incoming - before breakfast, during a missed lunch, on a long walk - and it reaches deeper, into confusion, personality change and seizures, because the brain itself runs short.
Diagnosis and treatment routes
An endocrinologist will pin the pattern down: symptom diary against meal timing, capillary or interstitial glucose during episodes, and Whipple's triad as the gate to further testing; only genuine, documented hypoglycaemia - particularly fasting - justifies the supervised 72-hour fast with insulin and C-peptide that diagnoses insulinoma. Reactive patterns get structured dietary change, which works well. If your episodes include fasting symptoms or confusion, seek assessment promptly; private endocrine appointments are typically available within about two weeks.
Seeing a specialist
Who to see, and how quickly you can be seen.
The specialist for this condition is usually a consultant endocrinologist. Your GP can refer you on the NHS, or you can arrange a private consultation directly.
A quiet reminder
This guide is for information, not medical advice.
Your GP knows your history and can tell you which parts apply to you. If in doubt, see them - and seek urgent care for any of the emergency symptoms described above.
Frequently asked
Common questions about Reactive hypoglycaemia vs insulinoma.
Quick, plain-English answers to what people ask us most.
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What is the difference between reactive hypoglycaemia and insulinoma?
Reactive hypoglycaemia is a common, usually benign dip in blood sugar two to four hours after eating, causing shakiness and sweating, while insulinoma is a rare insulin-producing tumour of the pancreas that causes true low blood sugar, often when fasting rather than after meals.
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What causes reactive hypoglycaemia versus insulinoma?
Reactive hypoglycaemia usually reflects an exaggerated but normal insulin response to certain meals, whereas insulinoma causes inappropriate, excessive insulin release regardless of when you last ate, which is the key distinguishing feature.
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What are the symptoms of each condition?
Both cause shakiness, sweating, hunger and sometimes confusion, but reactive hypoglycaemia symptoms cluster after meals, while insulinoma symptoms can occur at any time, characteristically worsening with fasting, such as first thing in the morning or after missing a meal.
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How is insulinoma distinguished from reactive hypoglycaemia?
The key test is documenting a genuinely low blood glucose level at the time of symptoms alongside inappropriately high insulin levels, often using a supervised prolonged fast, together with imaging to look for a pancreatic tumour if insulinoma is suspected.
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Is insulinoma dangerous?
Insulinoma is rare but can cause dangerously low blood sugar, including seizures or loss of consciousness if unrecognised, so it needs proper diagnosis and usually surgical removal, after which most people are cured.
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How is reactive hypoglycaemia managed?
Management usually involves smaller, more frequent meals with a lower glycaemic load, avoiding large amounts of refined carbohydrate on an empty stomach, and confirming the diagnosis with documented low glucose readings rather than relying on symptoms alone.
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Reactive hypoglycaemia vs insulinoma - which is more common?
Reactive hypoglycaemia-type symptoms are common, while insulinoma is genuinely rare, which is why doctors first look for documented true hypoglycaemia with symptoms before pursuing insulinoma-specific investigations.
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When should I see a doctor about possible insulinoma?
See a doctor if you have symptoms of low blood sugar particularly when fasting, or documented low glucose readings, so appropriate testing can be arranged. A private consultant endocrinologist can typically be seen within about two weeks to start this assessment.