Information about a laboratory test
High C-peptide may reflect increased endogenous insulin production or other factors such as kidney function.
Measures C-peptide, which is released in parallel with insulin made by the pancreas.
Used to assess endogenous insulin production and in selected evaluations of unexplained hypoglycemia or pancreatic conditions.
Low C-peptide can occur when endogenous insulin production is reduced; the simultaneous glucose level is important.
High C-peptide may reflect increased endogenous insulin production or other factors such as kidney function.
Use the performing laboratory's report and the sampling conditions first. Fasting status, timing, and whether the test is diagnostic or for monitoring can change interpretation.
>= 1.1 – <= 4.4 ng/mL
Example fasting reference interval
The source laboratory gives >=1.1–<=4.4 ng/mL as an example interval. Use the performing laboratory's own reference interval for an individual result.
Reference ranges may vary by laboratory, method used, age, sex, pregnancy status, and clinical context. The reference range on your own laboratory report takes precedence.
C-peptide remains in the blood longer than insulin. Fasting status and simultaneous glucose are important for interpretation.
Insulin in Blood — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2026 · Insulin blood testing and interpretation with glucose/C-peptide · Verified: Aug 12, 2026
C-Peptide Test — U.S. National Library of Medicine (MedlinePlus)
Government medical reference · 2026 · C-peptide use for endogenous insulin production and hypoglycemia context · Verified: Aug 12, 2026
C-Peptide — Labcorp
Reference laboratory test catalog · 2026 · Example fasting C-peptide reference interval and specimen preparation · Verified: Aug 12, 2026
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