Sample should be collected after an overnight fast (or during a hypoglycaemic episode). If a non-fasting c-peptide is specifically requested, refer the request to a Chemical Pathologist or Registrar before collecting the sample.
Collect an SST for C-peptide AND a fluoride oxalate tube for glucose estimation.
Send to the laboratory ASAP on COLD pack (NOT frozen pack). Sample must be received cold in the laboratory within 2 hours of collection.
GENERAL NOTES
Blood should be taken during a hypoglycaemic attack or after an overnight fast or glucagon stimulation test.
APPLICATION: Investigation of hypoglycaemia thought to be due to hyperinsulinism, particularly if surreptitious use of insulin is suspected. C-peptide can be measured as part of a glucagon C-peptide stimulation test for insulin reserve in NIDDM.
This test is performed each weekday. INTERPRETATION: Pancreatic beta cells secrete C-peptide with insulin,so inappropriately high levels of insulin and C-Peptide during hypoglycaemia indicate endogenous hyperinsulinism. Inappropriately high levels of insulin with low C-peptide during hypoglycaemia indicate exogenous hyperinsulinism.
