What is the role of C-peptide levels in differentiating type 1 and type 2 diabetes mellitus (DM)?

Updated: Sep 27, 2021
  • Author: Romesh Khardori, MD, PhD, FACP; Chief Editor: George T Griffing, MD  more...
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A fasting C-peptide level of more than 1 ng/dL in a patient who has had diabetes for more than 1-2 years is suggestive of type 2 diabetes (ie, residual beta-cell function). Stimulated C-peptide concentrations (after a standard meal challenge such as Sustacal or after glucagon) are somewhat preserved until late in the course of type 2 diabetes mellitus. Absence of a C-peptide response to carbohydrate ingestion may indicate total beta-cell failure.

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