| Everyone has what's called their "renal threshold" for glucose in the urine. Thats the level of glucose in the blood at which glucose "spills" into the urine. It's also called "kidney threshold", "spilling point", and "leak point." Although the average renal threshold for glucose is approximately 160-180mg/dL, the threshold varies greatly among individuals, and I've seen studies which put the renal threshold for many people as low as 150. Strangely enough, back when our only tests WERE urine tests, we had NO notion of any of this, no knowlegde of what the "one plus" "two plus" "three plus" "four plus" results of our urine tests meant. We had NO concept, for example, that a "negative" urine test could mean a blood glucose level of 150-180! The blue color was good, orange was really bad--that's all we kiddies knew back in the old days... Today, no doctors I know of use urine tests to diagnose diabetes, because without knowing the patient's renal threshold, you'd have no idea if the spilling of sugar meant only a borderline 150 or a much more dangerous 180+.
Michael  | 
