I want to ensure that my pancreas is producing normal insulin or not even though it may not be sufficient due to insulin resistance. I want to understand it, either to take treatment for increasing insulin sensitivity or for its frank deficiency or for both. Can a C-Peptide test serve my purpose since an insulin test may be useless because it might had been utilized or may also be exogenous? Can a C-peptide test can show false results due to the effect of insulin sensitizers or hypoglycemic medicines (because these may increase insulin secretions)? Is weight maintenance an indicator of normal insulin secretion?

It is true that the insulin blood test measures both endogenous insulin made in your pancreas and would measure insulin that you might have injected for treatment of the diabetes. For that reason, the measurement of C-Peptide is better for determining the production of endogenous insulin secretion. C-Peptide is only created in your body when proinsulin is cleaved to insulin plus C-Peptide. Therefore, for every molecule of insulin secreted, there is one molecule of C-Peptide secreted. It can only be an indicator of endogenous insulin secretion. What is generally done is to give some form of challenge to a patient. This can be in the form of a test meal, such as a can of a mixed meal with a can of Ensure or Sustacal or some other brand. It can also be done with a given load of oral glucose. Then, you measure C-Peptide levels after the challenge to determine whether you mount an adequate challenge of C-Peptide in response to the challenge. Check with your doctor as to which test they prefer and what the local normal values might be.

JTL