The Side Effects of Too Much Caffeine

The stimulant can have benefits, but there are downsides,


Verywell / Alexandra Shytsman

In This Article

Caffeine, usually in the form of coffee, tea, caffeinated sodas, and energy drinks, is often consumed to increase cognitive functioning and improve a bad mood. Indeed, many feel like they can't function until they get their first cup (or two) of coffee. Caffeine can have these benefits—and more—but there can be side effects to be aware of. Knowing how much may be too much can help you know when it might be time to pass on a refill.

The Perks

Many people simply love the taste and aroma of a good cup of Joe, and the caffeine that comes in coffee is an added bonus for those individuals. But there are many people who solely drink coffee or other caffeinated products for the jolt that it gives them.

Caffeine is a stimulant, and some studies show that small amounts of caffeine may improve your mental response time. Other studies show that caffeine doesn't just give you a momentary mental boost, but also has long-term effects on thinking skills.

Side Effects of Overconsumption

Most adults don't experience the effects of caffeine intoxication while drinking less than 250 milligrams of caffeine (about 2.5 cups of coffee) per day. You are more likely to experience negative side effects if you drink more than the recommended 400 milligrams per day.

The stimulant properties of caffeine increase your blood pressure and heart rate. Consuming too much may give you the "caffeine jitters," which is that jumpy and slightly alarmed feeling. Larger amounts of caffeine may make you irritable, sleepless, and may even trigger anxiety and cause diarrhea. Other side effects include:

  • Headaches
  • Anxiety and nervousness
  • Frequent urination
  • Incontinence
  • Upset stomach
  • Heart palpitations or fast heartbeat
  • Muscle spasms

Caffeine can act as a diuretic, so it was once assumed that drinking too much coffee or other caffeinated beverages would cause dehydration. However, researchers found that your body adjusts to your caffeine intake, so drinking caffeinated beverages won't increase your need for water.

Beware of caffeine pills and powders that promise to deliver a jolt quickly and effectively—they do exactly that. These products can deliver large doses of caffeine in a very short amount of time. People with underlying medical conditions should be particularly concerned as they could be more susceptible to the negative effects, such as heart palpitations.

What Amounts Are Considered Safe

If you have been wondering whether you need to curb your caffeine intake, first consider if you have noticed any particular sensitivities to caffeine. Take your medication use into consideration as well. Since caffeine can affect medication absorption and interact with certain medications, the following recommendations may or may not be appropriate for you (speak with your doctor).

General Population

It seems that experts who study caffeine agree that consuming up to 400 milligrams of caffeine per day is safe for healthy adults. That's roughly the amount of caffeine you get from four cups (not giant mugs) of coffee.

Pregnant or Breastfeeding Mothers

Breastfeeding or pregnant women may want to decrease that amount or skip caffeine altogether because, even though a mother may be able to handle the caffeine, the baby's barely developed metabolism still can't. There is also conflicting evidence on whether caffeine consumption during pregnancy leads to adverse birth outcomes, and so the American College of Obstetricians and Gynecologists (ACOG) suggests only a “moderate amount” of caffeine during pregnancy. That is defined as less than 200 milligrams per day.


Less is known about caffeine use in kids, but limiting or avoiding it is probably best. Since caffeine has an effect on the central nervous system as a stimulant, and children's brains are more sensitive to caffeine than adults, it may cause hyperactivity, anxiety, and affect sleep patterns.

Currently, the U.S. Food and Drug Administration (FDA) has no guidelines for caffeine consumption, but other countries suggest that kids age 4 to 6 years should have no more than 45 milligrams per day (that amount can be reached by consuming a 12-ounce cola).

Most experts recommend no more than 400 milligrams of caffeine per day for most adults. That equates to about 4 8-ounce cups of brewed coffee; 5 shots of espresso or 2 energy drinks. The recommendation changes for children and pregnant women.

Reducing Your Caffeine Intake

Kicking the caffeine habit cold turkey isn't recommended. Caffeine withdrawal can give you headaches, make you crabby, give you muscle aches, and generally make you feel miserable for a few days. The withdrawal symptoms will pass after a week or so, but blending regular caffeinated beverages with decaf for a few days might help with the transition.

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Article Sources
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  2. Can caffeine in my diet affect my pregnancy? Nutrition During Pregnancy. The American College of Obstetricians and Gynecologists

  3. Ozsungur S, Brenner D, El-sohemy A. Fourteen well-described caffeine withdrawal symptoms factor into three clusters. Psychopharmacology (Berl). 2009;201(4):541-8. doi:10.1007/s00213-008-1329-y

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