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1. Build one daily list
Write down each source, serving size, caffeine amount and time. Use the current product label where caffeine is declared. For café drinks, values are estimates because beans, recipe and serving size vary.
Do not subtract one source because it feels “natural”. Caffeine from coffee, tea, guarana or a supplement contributes to the same total.
2. Separate amount from timing
The daily total answers “how much”. Timing answers a different question: how much may still be active near sleep. Sensitivity and elimination vary between people.
A lower daily total taken late can feel more disruptive than a higher total taken early. Use the total calculator first, then review timing and sleep.
3. Know the boundaries
Population-level guidance cannot determine whether caffeine is appropriate during pregnancy, with a heart condition, anxiety, medicines or in a child. Those situations need a separate professional assessment.
Unexpected symptoms are not a reason to keep experimenting with a calculator. Stop and seek appropriate advice.