We’ve all heard the number: 400 milligrams of caffeine a day. The official FDA recommendation for most healthy adults is roughly three to four cups of brewed coffee. But here’s the truth: when it comes to caffeine, one size definitely doesn’t fit all.
Caffeine stories are regular headlines, especially when highly caffeinated drinks cause serious health scares. While some of that comes down to ignoring the limits, the bigger issue is personal sensitivity. Your unique biology, how quickly you metabolize caffeine, and even hidden sources in supplements or sodas can all shift your ideal intake. Some people thrive on a triple espresso, while others feel jittery after a small cup of green tea.
Caffeine works by blocking adenosine, a brain chemical that makes you feel sleepy. That’s why your morning cup delivers focus, energy, and a better mood. But too much? You might experience a racing heart, insomnia, anxiety, or just an uncomfortable, weird feeling.
“Caffeine hits peak levels about an hour after you drink it and can linger for hours,” says Dr. Nicholas Church, a board-certified family physician. “Some people are more sensitive than others, so listening to your body is important.”
While staying under 400 milligrams works for most, experts often recommend a more personalized approach based on body weight—about 1.36 mg per pound to enhance performance, and 4+ mg per pound as a ceiling before side effects appear. Pregnant individuals, those with heart issues, or people prone to anxiety should aim for under 200 mg.
Your true caffeine limit depends on you. If your heart’s pounding or you can’t sleep, it may be time to cut back—even if you’re well below the “official” max.
