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March 9, 2001

Diagnosis and Symptoms

Question from the Internet:

I have been insulin dependent for over 40 years and am on an insulin pump. When my primary insurance became Medicare, I had to have a C-peptide tests done which were 1.2 and 0.8 ng/ml. So, there was question as to whether I have type 1 or type 2 diabetes. Unfortunately, there are no endocrinologists here, and my internist put me on Glucophage and Avandia. He has suggested that I might not need to take insulin in three to six months. I have been taking these medications for about a week, and have noticed that I am starting to need fewer insulin boluses per day. Do you have any additional advice? What reactions should I expect?


I don’t know how old you are, nor your physical findings or past medical history, except you have been on insulin for more than 40 years (whether using a pump or conventional regimen doesn’t make a significant difference). One would say that it seems rather unlikely that you actually have type 2 diabetes. On the other hand, the C-peptide levels you report are not typical of a long-standing type 1 patient in whom residual endogenous insulin secretion is practically absent after 40 years. Furthermore, the positive effect of Glucophage [metformin] and Avandia on your boluses only, and not on your basal rates, would suggest the pills are having a positive effect on peripheral tissue insulin sensitivity rather than a stimulatory effect on endogenous residual insulin secretion.

To try to pinpoint a diagnosis, antibodies might be checked to exclude type 1A (autoimmune) (but they could be negative after 40 years) and a glucagon test to better assess endogenous secretion. In case of a residual secretion together with the absence of any autoantibody, one of the MODY (Maturity Onset Diabetes of the Young) types might be the answer, but to define which type a genetic test would be needed.

From the practical point of view, what matters is the best metabolic control (assessed by hemoglobin A1c) you are able to achieve with any therapy.