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Caffeine — timing, dose & interactions
Adenosine-receptor blocker that improves alertness and exercise performance. Counts whether it comes from coffee, tea, pre-workouts or pills.
Also known as Coffee, Caffeine pills
Timing
When to take it
Morning only — caffeine's half-life is ~5 hours, so afternoon doses disturb sleep.
Dose note. FDA: up to 400 mg/day is not generally linked to harm in healthy adults (less in pregnancy).
Interactions
Caffeine with other supplements
Safety
Medications & health conditions
Caffeine can raise blood pressure temporarily. The effect is smaller in regular users, but consider timing BP readings away from caffeine.
Limit caffeine in pregnancy. Common guidance is ≤200 mg/day from all sources during pregnancy.
Buying guide
What to look for on the label
Caffeine
- Coffee or tea counts
- If using pills, pair with L-theanine
FAQ
Common questions
When is the best time to take Caffeine?
On waking or Breakfast. Morning only — caffeine's half-life is ~5 hours, so afternoon doses disturb sleep.
Should Caffeine be taken with food?
It can be taken with or without food. Morning only — caffeine's half-life is ~5 hours, so afternoon doses disturb sleep.
Can you take Caffeine with L-Theanine?
Yes — it's one of the best-studied supplement pairings. Take them together in the morning. Avoid caffeine after early afternoon.
Can you take Caffeine with Iron?
Separate them — take iron at least an hour before your coffee or tea. Take iron on waking with water, and have coffee or tea at least 1 hour later.
Can you take Caffeine with Green Tea Extract?
Yes, but count the caffeine in the extract toward your daily total. Check the label; choose a decaffeinated extract if you already drink coffee.
Can you take Caffeine with Creatine?
Yes — current evidence suggests normal coffee intake is fine. No change needed for normal coffee drinkers. You can take them at different times if you like.
Sources
References
- 01U.S. FDA Consumer Update — Spilling the Beans: How Much Caffeine Is Too Much? (2018)