First I am sorry I did not run across your post last April. Do not worry at this point. We went through a very similar situation here and I can relate with the anguish that you likely feel. I have had t1 diabetes for 26 years and work as a product line rep for Accu-Chek. My wife is a pediatrician. We had a blood sugar reading in the mid 200s (mg/dl) on our 4 year old approx 1.5 years ago. Major panic. Did hand wash and many tests in sucession and they were in the mid to high 200s for approx 2 hours. Ketones were small. I was convinced that it was diabetes - I mean what else could it be? We immediately took her in for labs (insulin antibody, islet antibody, GAD, HBA1c, and one other that I can't remember. The more specific labs had to be done at Mayo clinic and it took approx 3 weeks for us to get the results back. It was total hell for me.
During the wait she actually tested her own blood sugar approx 6 times per day. All within normal ranges. Tests came back all a-ok and I was amazed, exstatic (sp) as well as absolutely f'n exhausted. One great thing happened as a result of this experience - it worked to draw me closer to God but that is for another board I guess
Anyway 6 months and one year later we followed this up with large glucose challenges (pancakes and a ton of syrup) as well as the more relaible 60g glucose intake and testing. No issue.
My wife (pediatrician) doesn't feel that normal blood sugar ranges are well understood by current medicine - especially in children. There are also degrees of normal.
Don't take to heart what others say. On the internet you are unable to guage the sources of information.
I hope things turned out well for you and your family. I am very interested to hear how things developed.