What Is a C-Peptide Blood Test?
C-peptide is released when the pancreas produces insulin. It measures your body's own insulin output.
Normal Range
- 0.8–4.0 ng/mL (fasting)
Low C-Peptide
- Type 1 diabetes
- Pancreatic failure
- Long-standing Type 2 (beta cell exhaustion)
High C-Peptide
- Type 2 diabetes — insulin resistance
- Insulinoma (rare tumor)
- Metabolic syndrome
Clinical Uses
- Distinguishing Type 1 from Type 2
- Evaluating residual pancreatic function
- Investigating hypoglycemia
Source: NLM MedlinePlus, American Association for Clinical Chemistry.
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