The most accurate reading for just a blood sugar stick would be after a 12-hour fast--obviously, what one is eating and when makes a big difference in glucose levels. If the person has eaten a bowl of ice cream, or a slab of pie, not that long before the blood test, the person may not be diabetic; that reading might even be expected.

Every time I get that glucose test--indeed, any time I get the standard blood work-up /chemistry panel--I make sure it's done early in the morning, after the overnight fast. Ditto for the multi-hour glucose toelrance tests (with concurrent insulin levels) that I do annually. To do it otherwise makes little sense.

Do you know if this person ever had a hemoglobin A1c test run? That measure is considerably less subject to wild temporary fluctuations caused by what has been ingested or what activities are being engaged in.