CPT Code:


Test Type: 1.0 mL Serum Kit Based
Stability Time:


Refrigerated:  3 days

Reference Range:
  • Low:  < 1.40 ng/mL
  • Optimal:  1.40 – 3.30 ng/mL
  • High:  > 3.30 ng/mL


Connecting Peptide (C-peptide) is a polypeptide produced by β-cells of the pancreas along with insulin. It serves as an accurate measure of insulin production, even in patients receiving insulin treatment.


Electrochemiluminescence immunoassay


Elevated C-peptide levels associated with:

  • hyperinsulinemia
  • insulin resistance
  • obesity
  • renal insufficiency


Decreased C-peptide levels associated with:

  • insulin deficiency
  • starvation
  • hypoglycemia
  • Addison’s disease
  • post pancreatectomy
  • High doses of biotin (> 5 mg/day) may interfere with assay results. Patient assumed to be refraining from biotin supplementation for at least 3 days prior to blood draw.

Collection Details:

Collection Instructions:

Preferred Specimen

1.0 mL serum (0.5 mL minimum) collected in serum separator tube (SST / Tiger Top)

Alternate Specimen

1.0 mL (minimum) plasma collected in EDTA plasma separator tube (Pearl Top)


Transport Temperature

Refrigerated (ship on frozen cold packs)