No checking urine sugar is practically of no value to monitor or detect Diabetes. Renal threshold - the concentration of glucose in blood above which Kidneys allow glucose to pass into urine may be different in different persons and may even be different in the same person at different times. The average Renal threshold is 300 mg/dl- that is above this level of blood glucose sugar is found in urine- But this level is already too high for a Diabetic person, hence it is not possible to monitor treatment using urine sugar levels. Sugar may be present in urine due to some other unrelated diseases like those of kidneys and thyroid. All the more that highly accurate glucometers are now available which give a better estimate of blood glucose at approx the same costs and can be used by the patients themselves; also see Testing Blood Glucose - urine glucose testing does not have a significant role to play in treatment and diagnosis of diabetes.

Also see related article- New drug to treat diabetes will help body loose glucose through urine.