Frequently Asked Questions (FAQs)

What is an insulinoma?

An insulinoma is a rare neuroendocrine tumour, usually in the pancreas. It releases insulin when the body does not need it. This can make blood glucose fall too low, causing hypoglycaemia, often called a hypo.

Most insulinomas are single tumours confined to the pancreas. Some can spread to other parts of the body. Treatment aims both to control low blood glucose and to treat the tumour.

Symptoms alone cannot confirm an insulinoma. Blood tests must show that the body is still releasing insulin when blood glucose is low. Scans are then used to find the tumour.

Source: ENETS 2023, questions 1, 5 and 6. Full reference below.

Could I have MEN1 Syndrome?

Multiple endocrine neoplasia type 1 (MEN1) is an inherited condition that can cause tumours in several glands, including the pancreas, parathyroid glands and pituitary gland. Having an insulinoma does not, on its own, mean that you have MEN1.

Your specialist will review your own medical history and your family history. A diagnosis at a young age, more than one pancreatic tumour, or other features of MEN1 may lead to a referral to a genetics specialist.

Genetic counselling explains whether testing is appropriate and what the results could mean for you and your relatives. Your team will arrange any other blood tests or checks needed.

Source: ENETS 2023, question 4. Full reference below.

What is insulin anyway?

Insulin is a hormone made by the pancreas. It helps the body use and store glucose from the blood.

Normally, insulin release falls when blood glucose becomes low. An insulinoma can continue releasing insulin at this point, causing blood glucose to fall further.

This is why doctors measure insulin alongside blood glucose. An insulin result within the laboratory’s usual range can still be too high for someone whose blood glucose is low.

Source: ENETS 2023, question 1. Full reference below.

What is Reactive Hypoglycaemia?

Reactive, or postprandial, hypoglycaemia means low blood glucose after eating. Several conditions can cause this, so the timing of a hypo does not establish its cause.

Most people with an insulinoma have hypos when they have not eaten, but some have them after meals. A small number have hypos only after eating. Therefore, hypos after meals do not rule out an insulinoma.

Your specialist may arrange a supervised mixed meal test, with blood samples taken before and after a meal. These tests help establish whether symptoms occur with genuinely low blood glucose and whether insulin release is appropriate.

Source: ENETS 2023, question 1. Full reference below.

What are the symptoms of an insulinoma?

The symptoms of an insulinoma usually come from low blood glucose. They can include sweating, hunger, weakness and a fast heartbeat.

When the brain does not receive enough glucose, a person may become irritable or confused, struggle to concentrate or have changes in behaviour. Severe hypoglycaemia can cause seizures or loss of consciousness. Some people lose their usual warning symptoms after repeated hypos.

Symptoms often occur overnight or when meals are delayed, but they can also happen after eating. Symptoms alone do not confirm an insulinoma: doctors need blood tests taken during an episode.

Emergency advice: if someone is unconscious or having a seizure, call 999. Do not give food or drink to someone who cannot swallow safely.

Is there a recommended diet for Insulinomas?

ENETS recommends eating regularly, with meals and snacks that include carbohydrates absorbed slowly, to avoid long gaps without food. Your specialist team or dietitian can help you plan the timing and amount of food around your pattern of hypos.

Food used to help prevent a hypo is different from treatment for a hypo that is already happening. Rapidly absorbed glucose or sugar is needed to raise blood glucose promptly when you are awake and can swallow safely. Follow the hypo treatment plan agreed with your team. Severe episodes may need emergency treatment.

Diet can help control symptoms, but it does not remove the tumour and may not prevent every hypo. Medicines or other treatments may also be needed. ENETS does not set one meal schedule or a list of foods that everyone must avoid.

Source: ENETS 2023, question 8. Full reference below.

What can cause hypos?

With an insulinoma, hypos happen because the tumour releases insulin when blood glucose is already low. They commonly occur during a gap without food, including overnight, although some people have hypos after meals.

Low blood glucose can also have other causes. These include certain medicines, some hormone deficiencies, insulin antibodies and changes after weight loss surgery. This is why a specialist reviews your symptoms, medicines and medical history before deciding which tests you need.

Keep to the eating, monitoring and treatment plan agreed with your team. A hypo does not mean that you have done something wrong. Repeated or worsening episodes need prompt medical review.

Source: ENETS 2023, questions 1 and 8. Full reference below.

Will I gain weight?

Weight gain is common in people with an insulinoma, but it does not happen to everyone. ENETS identifies a history of weight gain as a useful clue when assessing possible insulinoma.

People may need to eat more frequently to prevent or treat low blood glucose. Managing this can be difficult, especially while waiting for treatment.

The priority is to keep blood glucose safe. Discuss concerns about weight, food or activity with your specialist team or dietitian so that advice fits your needs. Avoid making changes that leave you without enough food to prevent hypos. There is no guarantee that weight gained will disappear automatically after treatment.

Source: ENETS 2023, questions 1 and 8. Full reference below.

What is Hypo Unaware?

Hypo unawareness means that you do not notice the usual warning signs when blood glucose falls. With repeated hypos, symptoms such as sweating or a fast heartbeat can become less noticeable or disappear.

You may then develop confusion or other serious symptoms without an early warning. Tell your specialist team if this happens.

ENETS notes that continuous glucose monitoring may help people with an insulinoma recognise falling glucose earlier, particularly when warning symptoms are absent. Your team should advise how to use the readings, when to check them with a blood glucose meter and how to respond.

A monitoring device helps with day to day management but cannot, on its own, diagnose or rule out an insulinoma. Ask your team for advice about driving and other activities where a hypo could put you or someone else at risk.

Source: ENETS 2023, questions 1 and 8. Full reference below.

How do I get a diagnosis?

See your GP if you have repeated symptoms that may be caused by low blood glucose. An endocrinologist, a specialist in hormones, can investigate the cause.

ENETS recommends checking for three things, known as Whipple’s triad: symptoms of a hypo, low glucose confirmed at the time, and improvement when glucose is raised.

To investigate an insulinoma, doctors measure glucose together with insulin and C peptide, a substance released when the body makes insulin. Insulin must be interpreted against the glucose level in the same blood sample, rather than simply labelled “high” or “normal”.

A diary of symptoms, meals and glucose readings can help describe what is happening. Home meters and continuous glucose monitors do not replace laboratory blood tests for diagnosis. Do not try to bring on a hypo or carry out a fasting test yourself.

Read more about diagnosing an insulinoma.

Source: ENETS 2023, question 1. Full reference below.

What tests will be used?

Blood tests: samples taken during low blood glucose measure glucose, insulin and C peptide, and sometimes proinsulin and ketones. Other tests can check for medicines or antibodies that may explain the result. If suitable samples have already confirmed the problem during a spontaneous hypo, a further fasting test may not be needed.

A supervised fast: this may last up to 72 hours, with repeated blood tests and close observation. ENETS recommends that it takes place in hospital on an endocrine ward. It ends according to the clinical protocol; not everyone needs the full 72 hours.

A mixed meal test: if symptoms occur after eating, blood samples may be taken before and for up to five hours after a meal.

Scans: once blood tests show inappropriate insulin release, CT or MRI scans help find the tumour. Endoscopic ultrasound can help detect small tumours and show how close they are to the pancreatic duct. Specialised PET scans may also be used.

If scans do not find it: a negative scan does not rule out an insulinoma. A specialist centre may consider GLP-1 receptor imaging or a calcium stimulation test with blood sampling from a vein draining the liver. The latter helps identify the area of the pancreas releasing excess insulin.

Source: ENETS 2023, questions 1 and 5. Full reference below.

How is an insulinoma treated?

For an insulinoma confined to the pancreas, surgery is usually the main treatment and can provide a cure. ENETS recommends preserving as much healthy pancreas as possible when this is technically safe.

Some tumours can be removed on their own, an operation called enucleation. Others require removal of part of the pancreas. The choice depends on the tumour’s size, position and distance from the main pancreatic duct, as well as your health. A tumour in the head of the pancreas does not automatically mean that a Whipple operation is needed.

Keyhole surgery should be considered where suitable. All pancreatic operations have risks, including leakage of pancreatic fluid. Your surgical team will explain the proposed operation, possible effects on pancreatic function and your recovery plan.

For selected people with a small insulinoma who are not fit for surgery, an expert centre may consider treatment using heat through an endoscopic ultrasound probe. ENETS notes that evidence about its longer term results is still limited.

While awaiting treatment, or when surgery is unsuitable, regular food intake and medicines can help control hypos. Diazoxide reduces insulin release. Some people may benefit from octreotide or lanreotide, but these medicines can worsen hypos in others, so an initial trial needs close glucose monitoring.

Source: ENETS 2023, questions 6 and 8. Full reference below.

What treatments are available for a malignant insulinoma?

A malignant insulinoma can spread beyond the pancreas. Care needs to address both the tumour and the low blood glucose it causes. A specialist neuroendocrine tumour team should plan treatment around your individual circumstances.

Options may include surgery, treatment directed at tumours in the liver, somatostatin analogue medicines, everolimus, chemotherapy or peptide receptor radionuclide therapy (PRRT). PRRT delivers radiation to tumour cells that have suitable receptors.

The choice depends on where the disease is, how quickly it is growing, scan findings and how well hypos are controlled. Treatments may be combined or used in sequence. ENETS describes capecitabine with temozolomide and combinations containing streptozotocin among chemotherapy options for selected pancreatic neuroendocrine tumours.

Source: ENETS 2023, question 8. Full reference below.

What happens afterwards?

Follow up depends on the tumour findings and whether treatment has completely removed it.

After complete removal of a localised insulinoma with no signs of malignancy and no grade 3 disease, ENETS recommends a review after three to six months. If symptoms have resolved, routine long term tumour follow up may not be needed. You should seek medical advice if symptoms of low blood glucose return.

This does not mean that everyone can stop follow up. People with remaining or metastatic disease, higher risk tumour features or an inherited condition need an individual plan from their specialist team. Care for recovery and any changes in pancreatic function may also continue.

Further treatment is based on the findings in your case. Chemotherapy or radiotherapy is not automatically required after an insulinoma operation.

Source: ENETS 2023, questions 4, 8 and 9. Full reference below.

Why do I feel this way?

While waiting for diagnosis or treatment

Low blood glucose can affect how you think, feel and behave. ENETS describes weakness, irritability and difficulties with thinking as possible symptoms. These effects can make everyday tasks and explaining your symptoms harder.

Tell your team about changes you notice and, where possible, whether they happen during a hypo. Symptoms should be assessed alongside glucose results. Ongoing low mood, anxiety or problems with concentration also deserve attention and should not automatically be put down to an insulinoma.

Before and after surgery

Discuss worries about treatment and recovery with your clinical team. Ask what support is available if emotional or practical difficulties are affecting you. ENETS 2023 does not provide a detailed guide to psychological recovery, and it does not promise that every symptom will disappear after surgery.

For emotional support, Samaritans can be reached free on 116 123, day or night.

Source for the effects of hypoglycaemia: ENETS 2023, question 1. Support contact checked with Samaritans.

Full reference

Hofland J, Falconi M, Christ E, Castaño JP, Faggiano A, Lamarca A, Perren A, Petrucci S, Prasad V, Ruszniewski P, Thirlwell C, Vullierme MP, Welin S, Bartsch DK. European Neuroendocrine Tumor Society 2023 guidance paper for functioning pancreatic neuroendocrine tumour syndromes. Journal of Neuroendocrinology. 2023;35(8):e13318. https://doi.org/10.1111/jne.13318.

The medical explanations on this page are based on the factual clinical information in this guidance. Emergency advice and the emotional support contact are linked separately above.

Page updated: 28 September 2026.