From the Guidelines
C-peptide testing is a crucial tool for assessing insulin production in people with diabetes, and it is used to check for diabetes, specifically to distinguish between type 1 and type 2 diabetes, as well as to evaluate beta cell function and guide treatment decisions 1.
Importance of C-peptide Testing
C-peptide testing measures the level of C-peptide, a protein fragment released when the pancreas produces insulin. This test is essential in determining the type of diabetes a person has, as well as in evaluating the function of the beta cells in the pancreas.
How C-peptide Testing is Used
To check C-peptide levels, healthcare providers typically order a fasting C-peptide test or a stimulated C-peptide test. Normal fasting C-peptide levels range from 0.5 to 2.0 ng/mL, but these values can vary between laboratories.
Interpretation of C-peptide Test Results
Low C-peptide levels indicate decreased insulin production, common in type 1 diabetes, while normal or high levels in someone with diabetes suggest insulin resistance (type 2 diabetes) 1.
Clinical Decision Making
For example, people with very low C-peptide levels will likely need insulin therapy, while those with higher levels might respond to oral medications that improve insulin sensitivity or stimulate insulin production. The test requires a simple blood draw, usually after fasting for 8-12 hours, and results are typically available within a few days.
Key Considerations
It is essential to note that C-peptide testing is only indicated in people receiving insulin treatment, and a random sample (with concurrent glucose) within 5 hours of eating can replace a formal C-peptide stimulation test in the context of classification 1.
Summary of Recommendations
In summary, C-peptide testing is a valuable tool for assessing insulin production in people with diabetes, and it should be used to guide treatment decisions and evaluate beta cell function 1.
From the Research
Enzymes Used to Check for Diabetes
- C-peptide (Connecting Peptide) is co-secreted with insulin and is used to assess functional β-cell mass 2
- C-peptide levels can be measured using various assays, including enzyme-linked immunosorbent assay (ELISA) and immunoradiometric assay (IRMA) 3
C-Peptide Measurement
- C-peptide measurement can be helpful in clinical practice to differentiate between type 1 and type 2 diabetes 4, 5
- C-peptide levels can be used to identify individuals at risk for or with type 1 diabetes with residual β-cell function 2
- C-peptide measurement can also be used to distinguish type 2 diabetes from Latent Autoimmune Diabetes in Adults and late-onset type 1 diabetes 2, 4
Assays Used for C-Peptide Measurement
- Ultrasensitive Mercodia enzyme-linked immunosorbent C-peptide assay (ELISA) 3
- Beckman immunoradiometric assay (IRMA) for C-peptide 3
- Time-resolved fluoroimmunoassay 6
- High-sensitivity commercial ELISA assay 2
Clinical Utility of C-Peptide Measurement
- C-peptide measurement can be used to assess endogenous insulin secretion in patients with diabetes 4, 5
- C-peptide levels can be used to predict clinical partial remission during the first year of type 1 diabetes 4
- C-peptide measurement can be used to assist in patient selection for islet cell transplantation and post-transplant monitoring 4