What is a fasting insulin test, and what is a normal insulin level?

What does the fasting insulin test measure?

An insulin in blood test measures insulin, a hormone made by the pancreas that helps control the amount of glucose in the blood. Normally insulin and glucose rise and fall together. MedlinePlus

Why is the fasting insulin test ordered?

• Mainly to find the cause of hypoglycemia (low blood glucose). MedlinePlus
• To help evaluate how much insulin the pancreas makes, or to help diagnose an insulinoma, an uncommon tumor of the pancreas. MedlinePlus

What are typical fasting insulin ranges?

ARUP Laboratories publishes this interval for its fasting insulin test. ARUP Laboratories

Reference ranges differ between laboratories and testing methods, and many also differ by age, sex, pregnancy or the phase of the menstrual cycle. The range printed on your own report is the one that applies to your result, and a clinician interprets it alongside your history.

MedlinePlus explains that a high insulin level with normal or slightly raised glucose may reflect insulin resistance, which is why insulin is interpreted together with glucose. MedlinePlus

What can affect fasting insulin results?

• You will probably need to fast for 8 to 12 hours before the test. MedlinePlus
• Biotin supplements need to be stopped for at least a day before the test, and insulin medicines can affect the result. MedlinePlus
• ARUP notes its assay reacts with some insulin analogs, which is one reason results from people using insulin are read differently. ARUP Laboratories

When should you talk to a clinician about a fasting insulin result?

• Your provider considers your history and other results, such as glucose, C-peptide or proinsulin, before concluding anything from an insulin value. MedlinePlus

DiscoverMedica explains what a test measures and what named sources publish. It does not interpret individual results; the clinician who ordered your test, or one you choose, does.

Where can you get a fasting insulin test?

A clinician can order it as part of routine or follow-up care. Some services also let you order lab tests yourself; check that a service’s panel includes this marker, which laboratory runs it, and who reviews the result with you.

• Function HealthAnnual membership for broad lab panels, drawn at Quest sites or at home.
• Quest HealthOrder individual lab tests from Quest Diagnostics online, without a doctor’s visit.

Fasting Insulin Test: questions, answered

Sources

1. MedlinePlus: Insulin in Blood
2. ARUP Laboratories: Insulin, Fasting (test 0070063)

Last reviewed October 7, 2026. Every source above was checked on or before that date. Educational information only, not medical advice; it does not replace a conversation with a licensed clinician. DiscoverMedica does not employ clinicians.