Testing For An Insulinoma
Confirming low blood glucose
Doctors look for symptoms, a laboratory confirmed low blood glucose result, and improvement when glucose rises. This is called Whipple’s triad. Home meters and glucose sensors cannot establish the diagnosis alone.
Blood tests
During low blood glucose, tests check whether insulin remains too high. Glucose, insulin and C-peptide (a marker of the body’s own insulin) are assessed together. Proinsulin and ketones may also be checked. Results are interpreted against blood glucose, not just normal ranges.
Supervised fasting test
If needed, a hospital fast lasts up to 72 hours, with repeated blood sampling and monitoring. It can finish earlier once diagnostic criteria are met. Do not attempt this test at home.
Mixed meal test
For symptoms after meals, specialists may take blood samples after a meal for up to five hours.
Other causes and scans
Your team considers medicines and other causes of hypoglycaemia. Scans help locate an insulinoma after blood tests support the diagnosis.
Full reference
Hofland J, Falconi M, Christ E, et al. 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
Based on Question 1. Updated 27 September 2026.