C-peptide (Serum) with 24-Hour Urine Collection

Why This Test Is Done

Doctors order this test to evaluate your pancreas’s ability to produce insulin naturally. It’s particularly useful for diagnosing type 1 diabetes, distinguishing between insulin-dependent and insulin-independent diabetes, and monitoring pancreatic health in conditions like pancreatitis or cystic fibrosis. It may also be used to assess insulin resistance or rule out other causes of high blood sugar.

What to Expect Before the Test

For the serum C-peptide test, you’ll typically provide a simple blood draw. For the 24-hour urine collection, you’ll collect all urine over a full day in a container provided by your healthcare team. Follow any specific instructions they give you to ensure accurate results.

What the Test Results Mean

Serum C-peptide levels indicate how much insulin your pancreas makes on its own. Lower levels may suggest insufficient insulin production (e.g., type 1 diabetes), while higher levels could indicate overproduction or resistance. Urine C-peptide (if measured) helps confirm excretion and overall metabolic balance. Your doctor will interpret these results in the context of your medical history and symptoms.

Common Conditions Monitored

This test is critical for diagnosing diabetes, assessing pancreatic diseases, and evaluating insulin therapy effectiveness. It may also help identify conditions like diabetes-related complications, autoimmune disorders affecting the pancreas, or metabolic syndromes.