C – Peptide

C - peptide is indirectly related to insulin, which is a structural part of proinsulin. Insulin and C-peptide are the final components of the active form of insulin, formed in the β-cells of the pancreas. The amounts of insulin and C-peptide secreted into the blood are equal in terms of molecule count, but the intact C-peptide remains in the blood longer than insulin. The ratio of C-peptide to insulin is usually 5:1. Determining C-peptide allows for a good assessment of the remaining β-cell function (after stimulation with glucagon or tolbutamide). This is convenient for patients previously treated with insulin. In clinical practice, C-peptide evaluation is used to determine the cause of hypoglycemia (e.g., suspecting insulinoma). C-peptide concentration may increase in cases of chronic renal failure. It may decrease in diabetes (Type 1) or with the use of exogenous insulin injections.

Recommendations:

• It is recommended to perform this test if there are symptoms of insulin metabolism disorders in the body as directed by a doctor, as well as suspecting a pancreatic tumor - insulinoma.
• The test is influenced by medications (insulin), diet, and illnesses.
• To take the test, one needs to come fasting for 2-3 hours.