Megadoses of vitamin C can alter reagent strip results; which specific parameter is most likely falsely decreased?

• A. Specific gravity
• B. Glucose
• C. Protein
• D. pH

Answer: (B)

Megadoses of vitamin C interfere with the colorimetric reactions used by urine reagent strips. The glucose test on these strips relies on an enzymatic reaction that generates a color change through hydrogen peroxide and a chromogen. Ascorbic acid acts as a strong reducing agent and can neutralize the reactive species or reduce the chromogen, leading to less color development. That makes the glucose result appear falsely decreased, even when glucose is present. Other parameters on the strip rely on different reactions or indicators that aren’t as susceptible to this reducing interference, so they are less likely to be falsely decreased.