How many cups of coffee a day are too many?

For some coffee drinkers, the day cannot begin without a cup, and one quickly becomes two, three or even four. Caffeine can improve alertness and concentration, but too much may bring a range of unpleasant health effects.

The Mayo Clinic says up to 400 milligrams of caffeine a day is considered safe for most healthy adults. That equals roughly four cups of brewed coffee, although the amount varies with the type of coffee, cup size and preparation method.

Too much caffeine can be associated with headaches, insomnia, nervousness, irritability, a rapid heartbeat, trembling and stomach problems. Some people feel these effects after much less than the general recommended amount. Sensitivity depends on factors including habitual caffeine use, how the body processes caffeine and certain medicines.

Caffeine is not found only in coffee. Tea, energy drinks, soft drinks, chocolate, some dietary supplements and certain medicines also contain it. About 237 milliliters of brewed coffee contains approximately 96 milligrams of caffeine, compared with about 48 milligrams in the same amount of black tea. Caffeine may also worsen anxiety, heartburn or certain urinary problems, and can affect the action of some medicines.

People who want to reduce their intake should avoid stopping abruptly. Headaches, fatigue, irritability and difficulty concentrating can follow a sudden reduction, though they usually disappear after a few days. A gradual approach, such as replacing one regular cup with a smaller serving or decaffeinated coffee, can make the adjustment easier. Even decaffeinated coffee contains small amounts of caffeine. Avoiding coffee later in the day may also help people whose caffeine use interferes with sleep.