What is caffeine?

Caffeine is a bitter, white substance that occurs naturally in more than 60 plants, including coffee beans, tea leaves and cacao pods (used to make chocolate). The U.S. Food and Drug Administration (FDA) considers caffeine to be both a food additive and a drug.

The most common sources of caffeine for most people are coffee, tea, soda and chocolate. The amount of caffeine in foods and drinks varies. For coffee and tea, the amount of caffeine per cup depends on the brand, the type of beans or leaves used, how it is prepared and how long it steeps. Most soda pops, not only colas, contain caffeine. Energy drinks are growing in popularity, particularly among teens and young adults. The caffeine content of these drinks ranges from 60 mg to more than 250 mg per serving.

Caffeine is the main ingredient in over-the-counter (non-prescription) stimulants that reduce fatigue (tiredness), increase alertness or give an energy boost. It is also added to other over-the-counter and prescription medications.

What effects does caffeine have on the body?

Caffeine passes into the bloodstream from the stomach and small intestine. Once in the bloodstream, caffeine stimulates the central nervous system -- the nerves, brain and spinal cord -- to make you feel more awake and alert. Caffeine reduces fatigue and improves focus and concentration. It also causes the release of acid in the stomach, and some people report heartburn or indigestion after consuming caffeine.

The effects of caffeine can be felt as soon as 15 minutes after it is consumed. The level of caffeine in the blood peaks about 1 hour later and stays at this level for several hours for most people. Six hours after caffeine is consumed, half of it is still in the body. It can take up to 10 hours to completely clear caffeine from the bloodstream.

How is caffeine used in medications?

Caffeine is a common ingredient in many prescription and over-the-counter headache remedies, pain relievers and cold medicines. Through caffeine’s effects on the central nervous system, it helps these drugs act more effectively -- and helps the body absorb headache medicines more quickly.

If you are concerned about your caffeine intake, read the product label on over-the-counter medications or the information sheet that comes with prescriptions to determine whether a medication contains caffeine. The FDA requires that the medication labels list the amount of caffeine they contain.

Caffeine is also found in some herbal products that people take as supplements, including guarana, yerba mate, kola nut and green tea extract. These products are not required by law to show their caffeine content on the label, and there is no set standard for caffeine content.

How much caffeine is too much?

The average American adult consumes 200 mg of caffeine a day. This is the equivalent of two 5-ounce cups of coffee or four 12-oz. colas. Consuming up to 400 mg or four cups of coffee, does not cause problems for most people. But caffeine affects people differently, depending on their size, gender and sensitivity to it. In people who are sensitive to caffeine, even moderate amounts can cause insomnia (trouble sleeping), rapid heart rate, anxiety and feelings of restlessness. Health and nutrition experts agree that consuming more than 600 mg of caffeine a day (equivalent of four to seven cups of coffee) is too much.

Teenagers and young adults often drink energy drinks and/or large amounts of strong coffee, putting them at risk of consuming too much caffeine.

What are the symptoms of having too much caffeine?

Symptoms of having too much caffeine include:

  • Headache, nervousness, dizziness
  • Having “the jitters” or feeling shaky
  • Insomnia or sleep that is ‘on and off’ throughout the night
  • Racing heart or abnormal heartbeat
  • Increase in blood pressure
  • Dehydration

Can an individual develop an addiction to caffeine?

Many people develop a tolerance for caffeine. This means that their body gets used to having caffeine every day. Over time, they must keep increasing their caffeine intake to achieve the desired effects of alertness and ability to concentrate.

What are some tips for breaking the caffeine habit?

Cut down slowly on the amount of caffeine in your diet. If you have developed a dependence on caffeine, an abrupt cutback can cause headache, fatigue, difficulty concentrating and even flu-like nausea and muscle pain. These symptoms are called ‘caffeine withdrawal.’ In general, the more caffeine you are used to consuming, the more severe withdrawal symptoms are likely to be. Symptoms of withdrawal begin 12 to 24 hours after the last caffeine intake and can last 2 to 9 days.

People who want to cut down on caffeine often make the mistake of stopping totally. When they experience withdrawal symptoms, they go back to drinking coffee or cola or taking a headache medication with caffeine in it to make the symptoms disappear. This starts the dependency cycle all over again. Avoiding the withdrawal symptoms is one of the most common reasons why people continue their caffeine habit.

To successfully reduce your caffeine intake, gradually reduce the amount of coffee, tea, soda and energy drinks you have each day. Begin to substitute cold caffeinated beverages with water. Water is a healthy choice and satisfies the need for drinking a liquid. Water also naturally flushes caffeine from your body and keeps you hydrated.

If you are a coffee drinker, gradually switch from regular coffee to decaf. First alternate between decaf and regular, then slowly change to more decaf and taper off regular coffee. Gradually reducing your caffeine consumption over a period of 2 to 3 weeks will help you successfully change your habit without causing withdrawal symptoms.

Last reviewed by a Cleveland Clinic medical professional on 07/13/2014.


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