EndocrineUpdated 2025-12-24Medically Reviewed
Fasting Insulin
Everything you need to know about Fasting Insulin levels, including what normal ranges look like and what abnormal results might indicate.
Standard Reference Range
Unit: µIU/mLMale Reference Range
2–20 µIU/mL
Female Reference Range
2–20 µIU/mL
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Reference ranges may vary slightly between laboratories. Always consult your doctor for interpretation.
What is Fasting Insulin?
Fasting insulin reflects how much insulin the pancreas secretes to maintain normal glucose. Elevated levels often indicate insulin resistance.
Key Takeaway
Pair fasting insulin with glucose (HOMA-IR) to quantify insulin resistance; falling insulin with stable glucose suggests improved sensitivity.
Why is this test performed?
- Assess insulin resistance or metabolic syndrome
- Evaluate hypoglycemia causes
- Monitor response to lifestyle or medication changes
Interpreting Your Results
- High: Insulin resistance, early type 2 diabetes, obesity, PCOS
- Low with High Glucose: Possible beta-cell failure (type 1 diabetes or late type 2)
- Low with Low Glucose: Potential insulin deficiency or adrenal insufficiency
Related Tests
- Glucose / HbA1c / Fructosamine: Glycemia metrics
- C-Peptide: Mirrors endogenous insulin secretion
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