Caffeine: How much is too much?

Caffeine has its perks, but it can pose problems too. Find out how much is too much and if you need to curb your consumption.

By Mayo Clinic Staff

If you rely on caffeine to wake you up and keep you going, you aren't alone. Caffeine is used daily by millions of people to increase wakefulness, alleviate fatigue, and improve concentration and focus.

How much is too much?

Up to 400 milligrams (mg) of caffeine a day appears to be safe for most healthy adults. That's roughly the amount of caffeine in four cups of brewed coffee, 10 cans of cola or two "energy shot" drinks. Keep in mind that the actual caffeine content in beverages varies widely, especially among energy drinks.

Although caffeine use may be safe for adults, it's not a good idea for children. Adolescents should limit caffeine consumption. Avoid mixing caffeine with other substances, such as alcohol.

Even among adults, heavy caffeine use can cause unpleasant side effects. And caffeine may not be a good choice for people who are highly sensitive to its effects or who take certain medications.

Women who are pregnant or who are trying to become pregnant and those who are breastfeeding should talk with their doctors about limiting caffeine use.

Read on to see if you may need to curb your caffeine routine.

You drink more than 4 cups of coffee a day

You may want to cut back if you're drinking more than 4 cups of caffeinated coffee a day (or the equivalent) and you're experiencing side effects such as:

  • Migraine headache
  • Insomnia
  • Nervousness
  • Irritability
  • Restlessness
  • Frequent urination or inability to control urination
  • Stomach upset
  • Fast heartbeat
  • Muscle tremors

Even a little makes you jittery

Some people are more sensitive to caffeine than are others. If you're susceptible to the effects of caffeine, just small amounts — even one cup of coffee or tea — may prompt unwanted effects, such as restlessness and sleep problems.

How you react to caffeine may be determined in part by how much caffeine you're used to drinking. People who don't regularly drink caffeine tend to be more sensitive to its negative effects. Other factors may include genetics, body mass, age, medication use and health conditions, such as anxiety disorders.

March 08, 2017 See more In-depth