Vasoactive intestinal peptide (VIP)
A gut hormone that, when produced in excess by a rare tumour (a VIPoma), causes profuse watery diarrhoea. The blood test is used when such a tumour is suspected — typically in someone with severe, persistent watery diarrhoea and a low potassium that has no ordinary explanation.
What it measures
Vasoactive intestinal peptide (VIP) is a hormone made by nerve and neuroendocrine cells in the gut and elsewhere. Among its actions, it makes the intestine secrete large amounts of water and salts into the bowel. The blood VIP test has one main clinical use: to investigate a rare neuroendocrine tumour called a VIPoma (usually in the pancreas) that produces VIP uncontrollably. The flood of VIP drives the intestine to pour out water and electrolytes, causing profuse, watery diarrhoea that continues even with fasting, together with dangerous losses of potassium and a tendency to dehydration — a picture sometimes called WDHA syndrome (watery diarrhoea, hypokalaemia, achlorhydria). When a VIPoma is present, the fasting blood VIP level is markedly high. So the test is ordered in the specific situation of severe, unexplained, persistent watery diarrhoea — particularly when accompanied by a low potassium — to look for this rare cause after the common ones (infection, medicines, inflammatory bowel disease, coeliac disease) have been considered. It is a specialist test, interpreted alongside chromogranin A, electrolytes and imaging.
What a high value can mean
- VIPoma — the key use; a VIP-secreting neuroendocrine tumour, usually of the pancreas, causing profuse watery diarrhoea.
- WDHA syndrome — the associated picture: watery diarrhoea, low potassium and low stomach acid.
- Rarely, other neuroendocrine tumours — can occasionally secrete VIP.
What a low value can mean
- Normal or low — the expected result; makes a VIPoma very unlikely and points diarrhoea toward commoner causes.
When to discuss with a doctor
Blood VIP is a highly targeted specialist test, not a routine one — it is ordered in the specific setting of severe, persistent, watery diarrhoea that continues despite fasting and is often accompanied by a low potassium, once the common causes have been excluded. A markedly high fasting level in that context suggests a VIPoma, a rare tumour needing specialist diagnosis (with imaging) and treatment, alongside urgent correction of the fluid and potassium losses, which can themselves be dangerous. Mediora.AI can surface a raised VIP and the accompanying low-potassium pattern from your results and flag it for review, but confirming a VIPoma is a specialist assessment — the interpretation belongs with your doctor.