Pre-test preparation or requirements
• Sample can be drawn at any time. No fasting or special preparation required.
• Sample should taken in plain vial.
1.0- 4.8 ng/ml
Significance of test
C-Peptide does not undergo significant hepatic extraction but is eliminated via renal system and therefore persists longer in the peripheral circulation. This result in a longer half-life (>30 minutes) and less fluctuation of C-peptide compared to insulin (5 minutes half-life).Hence, measurement of C-peptide can reflect pancreatic insulin secretion rate more accurately than insulin. C-peptide is used as an indicator of Beta-cell function in human subjects in a variety of conditions including type 1 diabetes, providing aid in the differential diagnosis of hypoglycemia, and in insulin self administration. A low C-peptide level is expected if the insulin secretion is diminished as in insulin-dependent diabetes (type 1 diabetes, latent autoimmune diabetes of adults (LADA) ). Elevated C-peptide levels may be found when Beta-cell activity is increased as in hyperinsulinism and insulinomas. The C-peptide/insulin molar ratio is considered as an estimation of hepatic clearance, if the liver is in insufficiency, insulin metabolism will be impaired, which will lead to abnormally large proportion of insulin in the peripheral circulation. Determination of the 24-hour urinary excretion of C-peptide is an additional option to monitor average Beta-cell insulin secretion. Urinary C-peptide level is a very important indicator in the evaluation of endogenous insulin secretin. C-peptide in the blood only reflect momentary C-peptide levels, while urinary C-peptide may reflect average level of C-peptide in blood overtime, meantime urine is much more convenient than blood to collect. As there is little negative effect of the proinsulin in urine, C-Peptide had no overlap between type 1 and 2 diabetes, therefore C-peptide in urine can better reflect the Beta-cell secretory function.