Sign in →

Test Code CPEPG C-Peptide, Serum

Reporting Name

C-Peptide, S

Useful For

Diagnostic workup of hypoglycemia:

-Diagnosis of factitious hypoglycemia due to surreptitious administration of insulin

-Evaluation of possible insulinoma

-Surrogate measure for the absence or presence of physiological suppressibility of endogenous insulin secretion during diagnostic insulin-induced hypoglycemia (C-peptide suppression test)


Assessing insulin secretory reserve in selected diabetic patients (as listed below) who either have insulin autoantibodies or who are receiving insulin therapy:

-Assessing residual endogenous insulin secretory reserve

-Monitoring pancreatic and islet cell transplant function

-Monitoring immunomodulatory therapy aimed at slowing progression of preclinical, or very early stage type 1 diabetes mellitus

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type


Specimen Required

Patient Preparation:

1. Patient should fast for 8 hours.

2. For 12 hours before specimen collection do not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.

Supplies: Aliquot Tube, 5 mL (T465)

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions: Centrifuge and aliquot serum into plastic vial within 2 hours of collection

Specimen Minimum Volume

0.75 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Frozen (preferred) 30 days
  Refrigerated  7 days

Reference Values

1.1-4.4 ng/mL

Reference intervals have not been formally verified in-house for pediatric patients. The published literature indicates that reference intervals for adult and pediatric patients are comparable.

Day(s) and Time(s) Performed

Monday through Friday; 5 a.m.-12 a.m.

Saturday; 6 a.m.-6 p.m.

Test Classification

This test has been cleared, approved or is exempt by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
CPR C-Peptide, S 13037-7


Result ID Test Result Name Result LOINC Value
CRPN C-Peptide, S 1986-9

Clinical Reference

1. Service FJ, O'Brien PC, Kao PC, Young WF Jr: C-peptide suppression test: effects of gender, age, and body mass index; implications for the diagnosis of insulinoma. J Clin Endocrinol Metab. 1992;74:204-210

2. Lebowitz MR, Blumenthal SA: The molar ratio of insulin to C-peptide. An aid to the diagnosis of hypoglycemia due to surreptitious (or inadvertent) insulin administration. Arch Int Med. 1993 Mar 8;153(5):650-655

3. Leighton E, Sainsbury CA, Jones GC: A practical review of C-peptide testing in diabetes. Diabetes Ther. 2017 Jun;8(3):475-487

4. Jones AG, Hattersley AT: The clinical utility of C-peptide measurement in the care of patients with diabetes. Diabet.Med. 2013 Jul;30(7):803-817. doi: 10.1111/dme.12159

5. Ahn CH, Kim LK, Lee JE, et al: Clinical implications of various criteria for the biochemical diagnosis of insulinoma. Endocrinol Metab (Seoul). 2014 Dec 29;29(4):498-504. doi: 10.3803/EnM.2014.29.4.498

6. Young DS, Huth EJ: SI Units for Clinical Measurement. American College of Physicians; 1998

Method Description

The Roche Elecsys C-peptide assay is a 2-site immunometric (sandwich) assay using electrochemiluminescence detection. Patient specimen, biotinylated monoclonal C-peptide specific antibody, and monoclonal C-peptide-specific antibody labeled with a ruthenium react to form a complex. Streptavidin-coated microparticles act as the solid phase to which the complex becomes bound. Voltage is applied to the electrode inducing a chemiluminescent emission from the ruthenium, which is then measured against a calibration curve to determine the amount of C-peptide in the patient specimen.(Package insert: Roche Elecsys C-peptide. Roche Diagnostics; V 1.0 English. 01/2020)

Analytic Time

Same day/1 day

Reject Due To

Gross hemolysis Reject
Gross lipemia OK
Autopsy specimen Reject

Method Name

Electrochemiluminescence Immunoassay (ECLIA)


If not ordering electronically, complete, print, and send a General Request (T239) with the specimen.