Skip to content

Use Caffeine Most Effectively

What's Your Caffeine Tolerance? (0:37)

Andrew Phillips, PhD, of Harvard, explains that caffeine tolerance varies from person to person.

The activating effect of caffeine depends both on the amount you consume and your individual response. Some people feel energized after a few sips, while others say consuming substantial amounts has little effect.

Moderate amounts of caffeine—up to 400 mg in 24 hours—have not been found harmful in most healthy adults. If you consume more caffeine than you normally do, you may find it makes you feel jittery and irritable, disrupts your sleep, upsets your stomach, makes your heart race, and causes muscle tremors.

Use just enough caffeine to keep yourself feeling alert and energized. That way, when you need an extra boost, you’ll get that benefit from a modest additional dose.