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What is caffeine?

Caffeine is a bitter substance that occurs naturally in more than 60 plants including

  • Coffee beans
  • Tea leaves
  • Kola nuts, which are used to flavor soft drink colas
  • Cacao pods, which are used to make chocolate products

There is also synthetic (man-made) caffeine, which is added to some medicines, foods, and drinks. For example, some pain relievers, cold medicines, and over-the-counter medicines for alertness contain synthetic caffeine. So do energy drinks and 'energy-boosting' gums and snacks.

Most people consume caffeine from drinks. The amounts of caffeine in different drinks can vary a lot, but it is generally

  • An 8-ounce cup of coffee: 95-200 mg
  • A 12-ounce can of cola: 35-45 mg
  • An 8-ounce energy drink: 70-100 mg
  • An 8-ounce cup of tea: 14-60 mg

What are caffeine's effects on the body?

Caffeine has many effects on your body's metabolism. It

  • Stimulates your central nervous system, which can make you feel more awake and give you a boost of energy
  • Is a diuretic, meaning that it helps your body get rid of extra salt and water by urinating more
  • Increases the release of acid in your stomach, sometimes leading to an upset stomach or heartburn
  • May interfere with the absorption of calcium in the body
  • Increases your blood pressure

Within one hour of eating or drinking caffeine, it reaches its peak level in your blood. You may continue to feel the effects of caffeine for four to six hours.

What are the side effects from too much caffeine?

For most people, it is not harmful to consume up to 400mg of caffeine a day. If you do eat or drink too much caffeine, it can cause health problems, such as

  • Restlessness and shakiness
  • Rapid or abnormal heart rhythm
  • Dependency, so you need to take more of it to get the same results

Some people are more sensitive to the effects of caffeine than others.


What are energy drinks, and why can they be a problem?

Energy drinks are beverages that have added caffeine. The amount of caffeine in energy drinks can vary widely, and sometimes the labels on the drinks do not give you the actual amount of caffeine in them. Energy drinks may also contain sugars, vitamins, herbs, and supplements.

Companies that make energy drinks claim that the drinks can increase alertness and improve physical and mental performance. This has helped make the drinks popular with American teens and young adults. There's limited data showing that energy drinks might temporarily improve alertness and physical endurance. There is not enough evidence to show that they enhance strength or power. But what we do know is that energy drinks can be dangerous because they have large amounts of caffeine. And since they have lots of sugar, they can contribute to weight gain and worsen diabetes.

Sometimes young people mix their energy drinks with alcohol. It is dangerous to combine alcohol and caffeine. Caffeine can interfere with your ability to recognize how drunk you are, which can lead you to drink more. This also makes you more likely to make bad decisions.

Who should avoid or limit caffeine?

Caffeine live stream

You should check with your health care provider about whether you should limit or avoid caffeine if you

  • Are pregnant, since caffeine passes through the placenta to your baby
  • Are breastfeeding, since a small amount of caffeine that you consume is passed along to your baby
  • Have sleep disorders, including insomnia
  • Have migraines or other chronic headaches
  • Have anxiety
  • Have GERD or ulcers
  • Have fast or irregular heart rhythms
  • Have high blood pressure
  • Take certain medicines or supplements, including stimulants, certain antibiotics, asthma medicines, and heart medicines. Check with your health care provider about whether there might be interactions between caffeine and any medicines and supplements that you take.
  • Are a child or teen. Neither should have as much caffeine as adults. Children can be especially sensitive to the effects of caffeine.

What is caffeine withdrawal?

If you have been consuming caffeine on a regular basis and then suddenly stop, you may have caffeine withdrawal. Symptoms can include

  • Headaches
  • Drowsiness
  • Irritability
  • Nausea
  • Difficulty concentrating

These symptoms usually go away after a couple of days.

  • Caffeine: How Much Is Too Much? (Mayo Foundation for Medical Education and Research) Also in Spanish
  • Nutrition and Healthy Eating: Caffeine (Mayo Foundation for Medical Education and Research) Also in Spanish
  • Spilling the Beans: How Much Caffeine is Too Much? (Food and Drug Administration) Also in Spanish
  • Tired or Wired? Caffeine and Your Brain (National Institutes of Health) Also in Spanish
  • Benefits of Java (Academy of Nutrition and Dietetics)
  • Caffeine and Alcohol (Centers for Disease Control and Prevention)
  • Caffeine and Migraine (American Migraine Foundation)
  • Caffeine: Can It Help Me Lose Weight? (Mayo Foundation for Medical Education and Research) Also in Spanish
  • Caffeine: How Does It Affect Blood Pressure? (Mayo Foundation for Medical Education and Research) Also in Spanish
  • Energy Drinks (National Center for Complementary and Integrative Health)
  • Truth About Energy Drinks (American Academy of Family Physicians) Also in Spanish
  • Update on Emergency Department Visits Involving Energy Drinks: A Continuing Public Health Concern (Substance Abuse and Mental Health Services Administration)
  • Caffeine (National Institutes of Health)

Journal Articles References and abstracts from MEDLINE/PubMed (National Library of Medicine)

  • Article: Caffeine ingestion improves specific artistic swimming tasks.
  • Article: Acute Effects of Caffeine Intake on Psychological Responses and High-Intensity Exercise...
  • Article: Spatial analysis of metformin use compared with nicotine and caffeine consumption...
  • Caffeine -- see more articles
  • National Institute of Environmental Health Sciences Also in Spanish
  • Caffeine and Your Child (Nemours Foundation) Also in Spanish
  • Caffeine Confusion (Nemours Foundation)
  • Caffeine in Pregnancy (March of Dimes Birth Defects Foundation) Also in Spanish
  • Caffeine in the diet (Medical Encyclopedia) Also in Spanish
  • Caffeine overdose (Medical Encyclopedia) Also in Spanish

Brand Name: NoDoz, Vivarin, Revive, Stay Awake, Enerjets, Lucidex
Generic Name: Caffeine
Companies: various generic manufacturers, Novartis Consumer Health, Inc. (NoDoz), GlaxoSmithKline Consumer Healthcare (Viviarin)

Medically reviewed by Philip Thornton, DipPharm. Last updated on March 19, 2021.

What is Caffeine?

Caffeine is a central nervous system stimulant. It works by stimulating the brain. Caffeine is found naturally in foods and beverages such as coffee, tea, colas, energy and chocolate. Botanical sources of caffeine include kola nuts, guarana, and yerba mate. Caffeine is also available in prescription and non-prescription medications.

Caffeine is used to restore mental alertness or wakefulness during fatigue or drowsiness. Caffeine is also found in some headache and migraine medications, in certain dietary supplements used for weight loss, and in many popular energy drinks.

Caffeine citrate (Cafcit) is available by prescription only. It is used for short-term treatment of neonatal apnea (breathing problems).

Caffeine may also be used for other conditions as determined by your health care provider.

Do NOT use caffeine:

  • if you are allergic to any ingredient in caffeine or caffeine products
  • in children less than 12 years of age; over-the-counter (OTC) caffeine formulations are not proven safe and effective for use in this age group
  • as a substitute for sleep

What Should I Know Before Using Caffeine?

Some medical conditions may interact with caffeine. Tell your health care provider if you have ANY medical conditions, especially if any of the following apply to you:
  • if you have allergies to caffeine, other medicines, foods, or other substances
  • if you are taking any prescription or nonprescription medicine, or herbal or dietary supplement
  • if you have anxiety, agitation or nervousness, liver or stomach (ulcer) problems, insomnia (trouble sleeping), seizures (convulsions), or heart disease, especially any abnormal heart rhythms or high blood pressure
  • if you are pregnant, planning to become pregnant, or are breast-feeding
Drug interactions may occur with caffeine. Tell your health care provider if you are taking any other medicines, especially any of the following:
  • Quinolones (i.e., ciprofloxacin)
  • Theophyllines
  • Duloxetine
  • Ephedra or Guarana
  • Rasagiline
  • Tizanidine

This is NOT a complete drug interaction list. Check with your health care provider before you start, stop, or change the dose of any medicine. A complete drug interaction check should be completed prior to your use of caffeine or any medication.

How Should I Use Caffeine?

Use caffeine as directed by your health care provider. If the medication is OTC, check the label on the bottle for the exact dosing instructions. If you have any questions about the use of an OTC medication, ask your pharmacist.
  • Caffeine may be taken with or without food. If caffeine upsets your stomach, take it with food.
  • Do not exceed the recommended dose of caffeine. Caffeine can be habit-forming.
  • Most OTC medications used for mental alertness contain 200 milligrams of caffeine per tablet or capsule. The usual maximum recommended dose of OTC caffeine is no more than 200 mg every 3-4 hours, or 1600 mg per day.
  • Do not double-up on your caffeine dose if you should miss the time for next dose.
  • The average cup of coffee contains 150-200 milligrams (mg) of caffeine per cup, while a cup of tea will have about 60 mg of caffeine. Cola products have about 30-40 mg of caffeine, and most energy drinks have about 60-70 mg. Be sure to account for any dietary caffeine that is consumed.

Ask your health care provider any questions you may have about how to use caffeine.

Important safety information:

  • Caffeine may cause dizziness. Do not drive or operate machinery, or engage in dangerous tasks until you know how caffeine might affect you.
  • Avoid large amounts of caffeine-containing foods and beverages, such as coffee, tea, cocoa, cola drinks, energy drinks and chocolate if you are taking higher doses of caffeine tablets. This also includes any herbal, dietary, or prescription medications that contain caffeine.
  • Caffeine is not to be used as a substitute for sleep.
  • Caffeine use may alter blood sugar levels. Diabetes patients should more closely regulate their blood sugar while taking caffeine.
  • Caffeine is not recommended for use in children less than 12 years of age. Safety and effectiveness in this age group have not been confirmed.
  • If you are pregnant, discuss with your health care provider if caffeine is appropriate for your use.
  • Caffeine is excreted into breast milk. Consult with your health care provider about the risks of using caffeine while you are breast-feeding. Caffeine may cause side effects in your baby.

Common side effects of Caffeine:

  • difficulty sleeping (insomnia)
  • nervousness or anxiety
  • irritability
  • nausea
  • headache

Seek medical attention right away if any of these severe side effects occur:

  • serious allergic reactions (difficult breathing, chest tightness, swelling of the mouth, face, lips, or tongue, rash, hives, or itching)
  • diarrhea
  • vomiting
  • rapid heart rate or palpitations
  • increased blood pressure
  • chest pain

This is not a complete list of all side effects that may occur. Call your health care provider for medical advice about side effects.

In case of overdose:

  • immediately contact your local poison control center, or emergency room
  • call 1-800-222-1222 (the American Association of Poison Control Centers).

Symptoms of overdose may include agitation; anxiety; confusion; frequent urination; irregular or fast heartbeat; muscle twitching; ringing in the ears; seizures; stomach pain; trouble sleeping.

Proper storage of Caffeine:

Store caffeine at room temperature, between 59 and 86 degrees F (15 and 30 degrees C), in a tightly closed container. Store away from heat, moisture, and light. Do not store in the bathroom. Keep caffeine out of the reach of children and away from pets.

General information:

  • If you have any questions about caffeine, please talk with your health care provider.
  • If your symptoms do not improve or if they become worse, check with your health care provider.
  • Check with your pharmacist about how to dispose of unused medicine.

This information is a summary only. Consult with your health care provider for additional questions or concerns about the use of caffeine.

More Caffeine resources

  • Caffeine Side Effects (in more detail)
  • Caffeine Professional Patient Advice (Wolters Kluwer)
  • caffeine Oral, Parenteral Advanced Consumer (Micromedex) - Includes Dosage Information
  • Cafcit Prescribing Information (FDA)
  • Cafcit Concise Consumer Information (Cerner Multum)
  • Caffeine; Caffeine and Sodium Benzoate Injection; Caffeine Citrate Monograph (AHFS DI)

Compare Caffeine with other medications for


1. Caffeine tablet [package insert]. Woonsocket, RI; CVS Pharmacy. 2011 August

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Popular FAQ

Does caffeine help migraines?

Caffeine has been shown to increase the effects of pain relievers like aspirin and acetaminophen for migraine headaches, increasing the effectiveness of these medicines by up to 40%. Continue reading

Does caffeine affect Vraylar?

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Caffeine is not listed as having a drug interaction with the atypical antipsychotic medicine Vraylar (generic name: cariprazine). However, Vraylar may lead to restlessness, the feeling the need to move around (akathisia), or trouble with sleeping (insomnia) in some patients. Call a health care provider right away if you or your family member has any of these symptoms while receiving Vraylar. Continue reading

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