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Test Code CPEP C-Peptide, Serum or Plasma

Important Note

Patient Preparation: For 12 hours before this test do not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.   Biotin can interfere with many immunoassay tests.

Additional Codes

Epic Order Code: LAB521
Sunquest Order Code: CPEP

Specimen Required

Container Type:


Inpatient: Mint

STAT: Mint

Outpatient: Gold

Acceptable: Red Top or Green Lithium Heparin.


Optimal Collection Volume: 

4.5 mL; Full Tube

Collection Instructions:

Gently invert sample 5-6 times after collection.

Processing Instructions: 

1. Allow serum sample to clot for 30 minutes.

2. Centrifuge specimen within 2 hours of collection.

3. Specimen tubes without a gel barrier should have the serum or plasma aliquoted to a false bottom container after centrifugation.

4. Keep serum/plasma refrigerated until testing can be performed.

Useful For

Levels are elevated in patients with insulinoma and decreased in patients with factitious hypoglycemia.

Method Name

Electrochemiluminescence Immunoassay

Stability Information

Specimen Type Temperature Time
Serum/Plasma Refrigerated 7 days
  Ambient  4 hours
  Frozen  30 days

Rejection Due To

Hemolysis Mild OK; Moderate OK; Gross Reject
Lipemia Mild OK; Moderate OK; Gross Reject
Icterus Mild OK; Moderate OK; Gross Reject
Other N/A


Post Processing Specimen Type


Preferred: Serum

Alternate: Plasma

Specimen Minimum Volume

Collecting minimum volumes can result in a need for sample recollection, and/or a delay in results. Minimum volumes are subjective and cannot account for all aspects of specimen and testing needs. Refer to the Specimen Required section for optimal volumes for laboratory specimens. Contact the Bronson Laboratory if complex collection exceptions occur that require more information.


Minimum Volume: 1 mL whole blood, 0.5 mL serum or plasma

Performing Laboratory

Bronson Laboratory, Chemistry - Kalamazoo

Day(s) Performed

Monday through Friday

Reference Values

 Test ID   Reference Range    Units      
CPEP 1.4 - 4.4 ng/mL

LOINC Code Information


CPT Code Information


Sample Retention Time

7 days