C-Peptide Test
2,160 Kshs | Home Collection Available
Synonyms
Connecting peptide, insulin c-peptide, proinsulin c-peptide
Purpose
The C-peptide test is a blood test that measures the level of C-peptide, a substance released into the bloodstream in equal amounts as insulin. It evaluates how much insulin the body is producing on its own.
C-peptide is a byproduct of insulin production. Measuring it helps distinguish between type 1 and type 2 diabetes, assess insulin resistance, and monitor pancreatic beta-cell function.
Other medical laboratory tests that can be performed alongside, fasting insulin levels, fasting blood glucose, HbA1c (glycated hemoglobin), oral glucose tolerance test (OGTT), autoantibody tests, and lipid profile.
Patient Preparation
The patient should fast for 14 to 16 hours for basal values.
Test Method
Chemiluminescence immunoassay
Samples
0.8 ml with a minimum volume of 0.3 ml of serum collected in a red top tube or gel barrier tube. Transfer the separated serum to a plastic transport tube if a red-top tube is used. Avoid haemolysis. The sample should be refrigerated.
Reference Range
1.1-4.4 ng/ml
Results Turnaround
Within 24 hours of receipt of samples.
Diseases / Diagnostic indicators
The C-peptide test helps assess how much insulin the pancreas is producing. It is particularly useful in evaluating different types of diabetes and identifying underlying conditions that affect insulin production or use. Here are some possible outcomes of the test,
High C-peptide levels
Indicate that the body is producing a large amount of insulin. This may occur in:
- Type 2 diabetes
- Insulin resistance
- Cushing’s syndrome
- Obesity
- Insulinoma (a tumor that secretes insulin)
- Chronic kidney disease (due to reduced clearance)
- Hypokalemia (low potassium levels)
Low C-peptide levels
Suggest little or no insulin production. This is commonly seen in:
- Type 1 diabetes (where the immune system destroys insulin-producing cells)
- Advanced stages of Type 2 diabetes
- After pancreatic surgery or in autoimmune pancreatic disorders
Normal C-peptide levels
Indicate a functioning pancreas, especially when matched with normal glucose and insulin levels. However, values must always be interpreted alongside other tests like glucose and insulin measurements, for accurate diagnosis. For more on C-peptide testing, read this study.