From the Guidelines
C-peptide testing is a crucial tool for assessing insulin production in people with diabetes, and it is typically performed using laboratory immunoassay techniques, not specific enzymes, as stated in the most recent guidelines 1.
Importance of C-peptide Testing
C-peptide testing measures the amount of C-peptide, a protein fragment released when proinsulin is converted to insulin in the pancreas. This test helps distinguish between type 1 and type 2 diabetes, as low C-peptide levels suggest type 1 diabetes, while normal or high levels typically indicate type 2 diabetes.
Normal C-peptide Levels
Normal C-peptide levels generally range from 0.5 to 2.0 ng/mL, but these values can vary between laboratories, as noted in the guidelines 1.
Determining Treatment Approaches
C-peptide testing is particularly useful when determining appropriate treatment approaches, such as whether insulin therapy is necessary. The test may be performed fasting or as part of a stimulation test where glucose is administered to observe the pancreatic response.
Recent Guidelines
According to the most recent guidelines, a C-peptide test is only indicated in people receiving insulin treatment, and a random sample with concurrent glucose can replace a formal C-peptide stimulation test in the context of classification, as stated in 1.
Key Considerations
It is essential to consider the circumstances of testing, and results showing very low levels do not need to be repeated, as noted in the guidelines 1. Additionally, C-peptide must be measured prior to insulin discontinuation to exclude severe insulin deficiency.
Consultation with Healthcare Provider
If you're concerned about diabetes management, consult with your healthcare provider about whether C-peptide testing would be beneficial in your specific situation, taking into account the most recent guidelines and recommendations 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