Question from Caldwell, New Jersey, USA:

My nine year old son has lost three pounds in the last two months and is skinny as a rail to begin with. His grandfather was Asian and had diabetes. He had a routine blood sugar of 133 mg/dl [7.4 mmol/L], four hours after only eating a peanut butter and jelly sandwich so l took him for another blood test. His fasting level was 101 mg/dl [mmol/L] and a two-hour postprandial (peanut butter and jelly sandwich plus a glass of milk) was 113 mg/dl [6.3 mmol/L]. I’m concerned that he did not have enough carbohydrates on the two-hour blood test to get an accurate reading. Should we ask for an oral glucose tolerance test?