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Insulin, C-peptide

Item Value
Test Update Information Effective March 15, 2011, C-peptide testing is being performed in-house using the same instrument-methodology (Siemens Centaur) that was used by Quest Diagnostics.
Approval req'd? No
Available Stat? No
Test code CPEP
Performed by China Basin Chemistry
Sendout? Yes
Method Chemiluminescent Immunoassay (Siemens Centaur)
Patient Preparation Overnight fast is required before specimen collection.
Collection Instructions Deliver to lab immediately. Call physician if patient is not fasting to see if the specimen is acceptable.
Container type Gold top or Red top
Amount to Collect 2 mL blood
Sample type Serum
Preferred volume 1 mL serum
Min. Volume 0.4 mL serum
Processing notes Separate serum from cells within 30 minutes of collection and freeze specimen at -20C.
Units ng/mL
Normal range
Fasting 0.8-3.1 ng/mL


Reference range was adopted from Quest Diagnostics-San Juan Capistrano based on in-house validation studies performed using the same instrument-methodology (Siemens Centaur) on samples from adult subjects with normal FBS (70-99 mg/dL) and A1c (4.3-5.6%).

Note: if patient was not fasting the normal ranges may not apply.

Pediatric reference ranges not available for this immunoassay platform.
Synonyms C-peptide
Stability Room temperature 1 day, refrigerated 1 week frozen at -20C 4 weeks, at -70C 1 year.
Turn around times Test performed Thursdays.
Additional information Obesity, high carbohydrate diet and inactivity increase levels of this hormone. The assay is cross-reactive with proinsulin, but not with insulin.

C-Peptide is useful in distinguishing insulin-secreting tumors, i.e., insulinomas, from exogenous insulin administration. C-Peptide concentrations are severely depressed or absent in Type I diabetes mellitus. It is also useful in monitoring patients who have received islet cell or pancreatic transplants.
CPT coding 84681
LOINC code 1986-9
Last Updated 9/19/2012 8:48:35 AM
Entry Number 148
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