Harvard Health Letter

Caffeine IQ: How much is too much?

Most people can drink a few cups a day. A higher intake may have negative side effects.

A daily caffeine jolt isn't usually harmful. It may have some health benefits. Caffeine can decrease fatigue and improve alertness, concentration, and motor performance. When added to painkillers, caffeine makes the drugs work faster and more efficiently.

But caffeine can also have negative effects on the body, such as insomnia, jitters, nervousness, dehydration, and irritability. Stopping caffeine intake suddenly can cause headaches, which can be cured by another jolt of caffeine, but may result in a dependence on the compound. Some antibiotics—ciprofloxacin (Cipro) and norfloxacin (Noroxin)—may interfere with the breakdown of caffeine, and some medications (such as theophylline, a bronchodilator) and supplements (such as echinacea) may cause side effects if taken with caffeine.

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