Question from Phoenix, Arizona, USA:

I am 51, male, have a BMI of 21.8 BMI, and am a dedicated exerciser. Blood numbers this year include a fasting glucose of 85 mg/dl [4.7 mmol/L]. All other standard panel blood values have been normal for years.

On a lark last month, I tried out a friend�s home glucometer after a meal, and my reading was higher than expected so I wanted to check further. I had an A1c test done at a laboratory, showing 5.4. Other laboratory test results (all fasting): insulin — 2.4 against a normal reference of 4.1 to 22.0; C-peptide –.9 against a normal reference of 1.1 to 4.6; and negative for GAD antibodies and for islet cell antibodies.

Peak post-prandial glucose is typically between 125 and 150 mg/dl [6.9 and 8.3 mmol/L]; but a load up on something with high sugar content will spike it to about 215 mg/dl [11.9 mmol/L] at 30 minutes. It�s always back between 80 and 100 mg/dl [4.4 and 5.6 mmol/L] within 90 minutes, no matter what I eat, or how high the early peaks. Fasting glucose remains in the 80s and 90s mg/dl [4.4 to 5.5 mmol/L]. I have no diabetic symptoms of any sort. I have not had an OGTT yet.

Relatively speaking, how low are my insulin (2.5) and C-peptide (.9) readings? Do they indicate I’ve got a ways to go before problems arise or is that quite diminished? Being negative on GAD and islet cell AB, what would be the next best test to see why I have diminished insulin output? My regular doctor tells me I’m apparently not all that far along with any disease and not to worry so much, but I’d rather deal with it now. For example, do you have any general comment on proactive, low-level insulin therapy for pre-diabetics in an effort to extend beta cell function?