This is the definitive test to find out how much insulin your own body is producing. The C-Peptide Fasting test measures a byproduct that is released in equal amounts to insulin. This "fasting" level provides a clear, baseline picture of your pancreas's true function. It is essential for distinguishing between Type 1 and Type 2 diabetes and for investigating the cause of hypoglycemia (low blood sugar). This simple blood test provides the root-cause data your doctor needs to create the right diabetes management plan for you.