What is the normal glucose level in urine?

• A. Negative
• B. Positive
• C. Trace
• D. High

Answer: (A)

Normally, urine contains no glucose because the kidneys reabsorb all filtered glucose in the proximal tubule. The glucose that is filtered at the glomerulus is taken back into the bloodstream by sodium-glucose transporters, so when blood glucose is within the normal range, none is left to appear in urine. Only when blood glucose rises above the renal threshold (about 160–180 mg/dL) or when the tubules aren’t functioning properly does glucose spill into urine, a condition called glucosuria. So a negative urine glucose test reflects normal physiology. If glucose is detected, it points to hyperglycemia or renal tubular dysfunction and would show as trace or positive depending on the amount.