Question from Fairbanks, Alaska, USA:

My adopted son had several hyperglycemic readings two hours after meals (160 to 240 mg/dl [8.9 to 13.3 mmol/L]) on my glucose meter which I use for my type 1. In response, his pediatrician checked his A1c and it was 5.2. Though this is in the normal range, she expected it to be 4.8 or below in a thin 5-year old so she referred us to a pediatric endocrinologist who did a whole set of testing. The results were all in the normal range, but just barely.

Fasting glucose: 86 mg/dl [4.8 mmol/L](normal)
Fasting insulin: 1.6, normal range: 0-13 uIU/mL
Fasting C-peptide:.5, normal range.4-2.2 ng/uL
Two-hour glucose tolerance test glucose (GTT): 133 mg/dl [7.4 mmol/L] (I checked his blood glucose at 1-hour and it was 227 mg/dl [12.6 mmol/L] on my meter)
Insulin autoantibody test: 19, normal range: <29 How do you interpret these results? Are these values, and the high readings on the meter, normal? Do kids who fall on this end of the spectrum often end up with full-blown diabetes? The endocrinologist would only say to keep checking his blood sugar a few times a week and to do a repeat GTT in six months. Would you do anything with his diet besides the small, frequent meals the endocrinologist recommended? I am especially interested in this as my son had an enormous calcium-oxalic kidney stone when he was four (diagnosed through hematuria) that took three surgeries to remove completely. I've read that excess sugar can promote stone formation and worry that even mildly elevated blood sugars might cause a new one to grow.