Lab Test

C Peptide

C-Peptide, Serum, C Peptide, Serum

Test Codes

Antrim #18205, EPIC: LAB5802, CPEP




The patient should be fasting prior to specimen collection.

Specimen Collection Criteria

Collect: One Gold-top SST tube. (Minimum Whole Blood: 2.0 mL)

Send specimen to the Laboratory immediately after collection for processing.

Physician Office/Draw Specimen Preparation

Let specimen clot 30-60 minutes then immediately centrifuge to separate serum from cells. Transfer serum to a plastic transport tube and freeze (-20°C/-4°F or below) immediately. (Minimum Serum: 0.5 mL)

Preparation for Courier Transport

Transport: Serum aliquot, frozen (-20°C/-4°F or below). (Minimum Serum: 0.5 mL)

Rejection Criteria

  • Samples that have not been collected and processed as indicated. 
  • Plasma specimens. 
  • Severely lipemic, icteric, or hemolyzed specimens. 

In-Lab Processing

Tubes are placed on the Abbott input / output module for centrifugation and testing by the automated line instruments.


Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): Unacceptable
Refrigerated (2-8°C or 36-46°F): 48 hours for inpatients only.
Frozen (-20°C/-4°F or below): 7 days

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days


Royal Oak Automated Chemistry Laboratory


Monday – Friday.
Results available within 2 business days.

Reference Range

Fasting: 0.8-5.2 ng/mL.

Test Methodology



Insulin and C-Peptide are released in equimolar amounts from the beta cells of the pancreas. The half-life of insulin and C-Peptide is 5-10 minutes and 30-35 minutes, respectively. Because of this longer half-life, C-Peptide levels are often used as an indicator of beta-cell function. It has been demonstrated that individuals with type 1 diabetes who maintain higher C-Peptide levels have fewer complications.

Clinical Utility

C-Peptide levels may aid in distinguishing type 1 and type 2 diabetes. C-Peptide is also useful in the determination of endogenous insulin secretion and the diagnosis of insulinoma.

In insulinoma, C-Peptide levels should parallel those of insulin. Factitious hyperinsulinism (i.e., exogenous insulin administration) will have high insulin but low C-Peptide levels.

CPT Codes

LOINC: 1986-9


Last Updated


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