My 12 year old son weighs 35 kg (77 pounds) is on Human Mixtard 30/70 (7 units in the morning and 4 units at night), and when he is tired and has symptoms of low sugar, his urine sugar is three-plus or more, but his blood sugar is around 60-80 mg/dl [3.3-4.4 mmol/L]. What is the cause of this? How can we distinguish between high and low blood sugar?

The apparent disparity between the glucose in the urine and the blood level is almost certainly because at the time the urine was filtered through the kidney the blood sugar would have been over 180 mg/dl [10 mmol/L]. However, the blood sugar sample could well have been taken an hour or two later, and the level could easily have dropped in the interim.

What is perhaps of more importance is that your son is having blood sugars as low as 60mg/dl [3.3 mmol/L] on a total dose of insulin that is only about one third of the normal for a boy of his weight with type 1A (autoimmune) diabetes, which is the most common form. I think that you should review with the endocrinologist both the exact diagnosis as well as the technique for measuring blood sugar.The difference between low and high blood sugar levels can only be decided by using one of the devices for home blood glucose monitoring.

DOB