Educational information only. At Precursor, blood testing is requested and reviewed by a clinician and considered alongside your history and other markers, not as a stand-alone diagnosis. Testing is performed in NATA-accredited laboratories to ISO 15189 standards.

What is C-peptide?

C-peptide is released by the pancreas in equal amounts to insulin, as a by-product of making it. Because it is cleared more slowly and steadily than insulin, measuring C-peptide gives a reliable picture of how much insulin your own pancreas is producing, even in people who take insulin as medication.

Why it matters

C-peptide helps distinguish how much of the insulin in your body is made by your own pancreas versus given from outside. Clinicians use it to understand pancreatic function and to help characterise the type and stage of blood-sugar problems, making it a useful complement to glucose and insulin.

What your results can mean

Higher than optimal

A high C-peptide indicates the pancreas is producing a lot of insulin, which often accompanies insulin resistance. It is interpreted alongside glucose to understand the wider metabolic picture.

Lower than optimal

A low C-peptide suggests the pancreas is producing less insulin. The meaning depends heavily on context, which is why this marker is always read by a clinician rather than in isolation.

Reference ranges in Australia

C-peptide is reported in nanomoles per litre (nmol/L) or micrograms per litre, depending on the laboratory, and is interpreted in relation to your blood glucose at the time of the sample. Read your result against the range and units on your own report.

Test your C-peptide with Precursor

C-peptide only makes sense alongside your glucose and insulin. At Precursor, metabolic testing is requested and reviewed by a clinician within Full Advanced Bloods, a single draw covering your metabolic, heart, hormonal, kidney, liver, thyroid and nutrient markers together, so your pancreatic function is read in full context.