Which statement describes the caffeine-related diuretic effect?

• A. Diuretic effect occurs with higher intake and is observed above 4 mg/kg
• B. Diuretic effect occurs with any caffeine intake
• C. There is no diuretic effect from caffeine
• D. Diuretic effect only occurs when dehydrated

Answer: (A)

Caffeine’s diuretic effect depends on how much is consumed. At higher doses, caffeine can increase urine production, while smaller amounts rarely cause a noticeable diuretic response. The threshold commonly cited is around 4 mg of caffeine per kilogram of body weight; above this, diuresis is typically observed. Mechanistically, caffeine blocks adenosine receptors in the kidneys, which can raise glomerular filtration and reduce water reabsorption, leading to more urine. Habitual caffeine users may develop tolerance to this effect, so the diuretic response is less pronounced for regular drinkers. Dehydration isn’t required for this effect to occur; it’s primarily a function of dose.