What Is C-Peptide?
C-peptide is released in equal amounts to insulin when your pancreas produces it. Measuring C-peptide shows how much insulin your body is actually making, even if you are taking insulin injections.
Normal C-Peptide Range
| Test | Normal Range |
|---|---|
| Fasting C-peptide | 0.5–2.0 ng/mL |
| Fasting Insulin (paired) | 2–25 µIU/mL |
Why It's Ordered
- Distinguishing Type 1 from Type 2 diabetes
- Evaluating unexplained low blood sugar (hypoglycaemia)
- Assessing pancreatic insulin-producing capacity
- Monitoring insulinoma (insulin-producing tumour)
What Low C-Peptide Means
Low levels suggest the pancreas is making little or no insulin — typical in Type 1 diabetes or advanced Type 2 diabetes.
What High C-Peptide Means
High levels suggest the pancreas is overproducing insulin, seen in early Type 2 diabetes, insulin resistance, or rarely an insulinoma.
Important: C-peptide results must be interpreted alongside blood glucose levels and clinical history by your doctor.