C-peptide levels are high in which condition?

• A. DM1
• B. DM2
• C. Exogenous insulin administration
• D. Hypoglycemia due to insulin therapy

Answer: (B)

C-peptide reflects endogenous insulin production because it’s released in the same amount as insulin when proinsulin is cleaved, and it isn’t present in injected insulin. High C-peptide means the body is producing a lot of its own insulin. In type 1 diabetes, beta cells are damaged and endogenous insulin production drops, so C-peptide is low. In type 2 diabetes, insulin resistance prompts the pancreas to produce more insulin, so C-peptide can be normal to high. When insulin is given as medication, there’s insulin without C-peptide, so C-peptide stays low. Hypoglycemia from insulin therapy also tends to suppress endogenous insulin, keeping C-peptide low. Thus, the condition with high C-peptide among the options is type 2 diabetes.