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Test Code CPEP C-Peptide, Serum

Performing Laboratory

Northwell Health Laboratories



Reference Values

0.9-7.1  ng/mL

Test Classification and CPT Coding


Day(s) and Time(s) Performed

Monday through Friday

Physician Office Specimen Requirements

Container/Tube:  Gold-top tube(s)

Specimen: 2 mL serum ( 1 mL min)

Transport Temperature: Frozen Serum



12 hours before this test do not take multivitamins or dietary supplements containing biotin or vitamin B7, which are commonly found in hair, skin, and nail supplements and multivitamins


Computer Interface Code

PDM #  5900100

Used 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