There is a condition called Low Renal Threshold. This sounds like it. It's where the kidneys don't recover all the glucose from the blood, even if it's not actually very high.. It's quite different from Diabetes Insipidus, which involvesexcessive urination, without glucose..
To the best of my memory, LRT doesn't cause any harm and doessn't need treating. Go back and discuss with the doctor.
Hana