How often is a C-peptide test done on a person with diabetes?

In the human islet cells, the first insulin like molecule to be made is preproinsulin which degrades to proinsulin, and in turn is passed into the blood stream as equal parts of insulin and C-peptide. C-peptide measurement can thus be used as an index of how much of endogenous insulin a person with diabetes may still be making when they are also taking subcutaneous synthetic insulin.

In type 1A (autoimmune) diabetes, the test is occasionally used to see if hypoglycemia might be due to delayed first phase insulin release from remaining but damaged islet cells. The test may also be helpful in differentiating antibody negative type 1B diabetes from type 2 diabetes in someone who is already on insulin.

DOB

[Editor’s comment: In any of the circumstances described by Dr. O’Brien, obtaining a C-peptide level is worth consideration, but it is not a test that would be done routinely on a scheduled basis for most people with diabetes.

WWQ]