Question from Bristol, Virginia, USA:

My four year old son has Down Syndrome, congenital glaucoma, and hypothyroidism. In May of this year and one time after that, he was in the Emergency Room for blood sugars in the 40s mg/dl [2.2 to 2.7 mmol/L]. Our primary care doctor gave us a testing kit and told me to start keeping an eye on it. His blood sugar has only been that low two or three times, but mostly in the 180 to 400 mg/dl [10.0 to 22.2 mmol/L] range. I’ve called the doctor back and been back in several times the last few months. They’ve made him an appointment for a pediatric endocrinologist, but went ahead and gave us a NovoLog injection pen and a written sliding scale for directions on these highs. They have not made an “official” diagnosis. Starting last Friday and until Tuesday his levels were 200 to 400 mg/dl [11.1 to 22.2 mmol/L] even with injections every four or five hours. On Wednesday of this week, they started coming back down to 95 to 150 mg/dl [5.3 to 8.3 mmol/L]. Why the big variability? Does my son definitely have diabetes?