In a patient with diabetes who takes megadoses of vitamin C, which result on a glucose pad of a urine reagent strip is most likely?

• A. Normal reading
• B. Falsely low
• C. Falsely high
• D. No change

Answer: (B)

High-dose vitamin C can interfere with the glucose pad on a urine reagent strip. These strips rely on an enzymatic reaction that ultimately produces a color change proportional to glucose amount. Ascorbic acid is a strong reducing agent and can neutralize the reactive species (like hydrogen peroxide) or reduce the chromogen, dampening the color development. That makes the result appear lower than the actual glucose level, yielding a falsely low reading. It wouldn’t cause a true high result, and while it can mask glucose, a normal reading isn’t reliable in this context when megadoses of vitamin C are present.