Does adding water to coffee decrease the effects of caffeine?

Adding water to brewed coffee does not significantly decrease the effects of caffeine.

While diluting coffee with water reduces its concentration, the overall amount of caffeine remains the same.

The caffeine content in coffee is primarily determined by the type of beans used, the brewing method, and the amount of coffee grounds. Although diluting coffee may result in a lower concentration of caffeine per sip, the total caffeine consumed will still be comparable if you drink a larger volume of the diluted coffee to match your usual serving.

If you're sensitive to caffeine and are trying to reduce its effects, consider using less coffee grounds when brewing or switching to lower-caffeine coffee alternatives like decaf or herbal tea.