Professional and Linguistic Assessments Board (PLAB) Practice Exam

What level of C-peptide is typically found in patients with type 1 diabetes?

1. Elevated

2. Normal

3. Low

4. Variable

The correct answer is: Low

In patients with type 1 diabetes, the body's immune system mistakenly attacks and destroys the insulin-producing beta cells in the pancreas. This destruction leads to significantly reduced or absent insulin production. C-peptide is a byproduct of insulin production; it is released into the bloodstream when proinsulin is cleaved to form insulin. Since individuals with type 1 diabetes generally have minimal or no insulin production due to the loss of beta cell function, the corresponding C-peptide levels are low. This is a key distinction in diagnosing and differentiating between type 1 and type 2 diabetes, as type 2 diabetes typically presents with normal or elevated C-peptide levels due to increased insulin resistance followed by eventual beta cell dysfunction. Therefore, low C-peptide levels align with the underlying pathology of type 1 diabetes, making this the correct answer.