EndocrineUpdated 2025-12-24Medically Reviewed
C-Peptide
Everything you need to know about C-Peptide levels, including what normal ranges look like and what abnormal results might indicate.
Standard Reference Range
Unit: ng/mLMale Reference Range
0.8–3.1 (fasting) ng/mL
Female Reference Range
0.8–3.1 (fasting) ng/mL
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Reference ranges may vary slightly between laboratories. Always consult your doctor for interpretation.
What is C-Peptide?
C-Peptide is released in equal amounts to insulin when the pancreas makes insulin. Measuring it differentiates endogenous insulin production from injected insulin.
Key Takeaway
Low C-peptide with high glucose suggests beta-cell failure (type 1 diabetes); high C-peptide indicates insulin resistance or insulinoma.
Why is this test performed?
- Distinguish type 1 from type 2 diabetes
- Evaluate hypoglycemia causes
- Monitor beta-cell function after islet or pancreas transplant
Interpreting Your Results
- Low: Type 1 diabetes, late-stage type 2, pancreatic damage
- High: Insulin resistance, insulinoma, sulfonylurea use
Related Tests
- Insulin / Glucose / HbA1c / Fructosamine: Glycemic context
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