C-Peptide CPT: 84681


Connecting Peptide

Insulin C-Peptide

Proinsulin C-Peptide

Special Instructions

This test may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin (also termed as vitamin B7 or B8, vitamin H, or coenzyme R). It is recommended to ask all patients who may be indicated for this test about biotin supplementation. Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.

Expected Turnaround Time

Within 1 day

Specimen Requirements




0.8 mL

Minimum Volume

0.3 mL (Note: This volume does not allow for repeat testing.)


Red-top tube or gel-barrier tube.


If a red-top tube is used, transfer separated serum to a plastic transport tube. Avoid hemolysis.

Storage Instructions


Stability Requirements

Temperature Period
Room Temperature 24 Hours
Refrigerated 5 Days
Frozen 4 Weeks
Freeze/thaw/ cycles X 3

Patient Information

To help evaluate insulin production by the beta cells in the pancreas or to help determine the cause of low blood glucose (hypoglycemia).

When you have diabetes and your health practitioner wants to determine if you are producing enough of your own insulin or there is an absolute need for insulin injections or an insulin pump; when your health practitioner suspects that you have insulin resistance or your diabetes has been incorrectly classified; when you have documented hypoglycemia and your health practitioner is investigating causes.

A blood sample is obtained by inserting a needle into a vein. If a 24-hour urine sample is required, all urine produced over a 24-hour time period will be collected.

Fasting for 8 to 10 hours before blood testing is usually required. In some cases, your healthcare practitioner may want to examine C-peptide production after a formal stimulation test in which you will be administered a standardized amount of a meal or substance that stimulates the pancreas.