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Editor: Jacqueline L. Longe
Date: 2018
Publisher: Gale, a Cengage Company
Document Type: Drug overview
Length: 1,580 words

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Caffeine is a drug and component of certain foods that stimulates the central nervous system (CNS).


Caffeine makes people more alert, improves coordination, and keeps people from becoming drowsy. Caffeine is combined with certain headache pain medicine to make the drug work more quickly and effectively. Caffeine alone can also help relieve headaches. Antihistamines are sometimes combined with caffeine to counteract the drowsiness caused by those drugs. Caffeine is also sometimes used to treat other conditions, including breathing problems in newborns and in young babies after surgery.


Caffeine can be found in plants (coffee, tea, cocoa, kola nuts) and is added to certain foods and beverages, such as soda and energy drinks. Caffeine is also available in a medication form at pharmacies and is a part of some medications.

Kola can be prepared in decoction or tincture form. To prepare a decoction, mix 1–2 tsp of powdered kola nut in a cup of water. After bringing the water to a boil, simmer the decoction on low heat for 10–15 minutes. Tinctures of kola nut can be purchased at many health food stores or mail order suppliers. A tincture is an herbal preparation made by diluting the herb in alcohol, glycerin, or vinegar. Dosage of kola tincture varies by formula and the symptoms or illness it is supposed to treat, but an average recommended dosage might be 1–4 mL three times daily. Powdered kola nut and kola tinctures should be stored in airtight containers away from direct light to maintain potency.

For over-the-counter caffeine preparations, adults should take 100–200 mg no more than every three to four hours. In timed-release form, the dose is 200–250 mg once a day. Timed-release forms should not be taken less than six hours before bedtime. Dosage of caffeine for treating headaches should be discussed with a physician.


Caffeine containing foods.

Caffeine containing foods.
(Charles D. Winters/Science Source)

If caffeine is administered in a kola preparation, kola should always be obtained from a reputable source that observes stringent quality control procedures and industryaccepted good manufacturing practices. Consumers should look for the designations USP (U.S. Pharmacopeia) or NF Page 636  |  Top of Article(National Formulary) on kola nut labeling. Herbal preparations prepared under USP or NF guidelines meet nationally recognized strength, quality, purity, packaging, and labeling standards as recommended by the U.S. Food and Drug Administration (FDA).

Caffeine cannot replace sleep and should not be used regularly to stay awake as the drug can lead to more serious sleep disorders, such as insomnia.

People who use large amounts of caffeine over long periods build up a tolerance to it. When that happens, they have to use more and more caffeine to get the same effects. Heavy caffeine use can also lead to dependence. If an individual stops using caffeine abruptly, withdrawal symptoms may occur, including headache, fatigue, drowsiness, yawning, irritability, restlessness, vomiting, or runny nose. These symptoms typically persist for a week.

If taken too close to bedtime, caffeine can interfere with sleep. Even if it does not prevent a person from falling asleep, it may disturb sleep during the night.

Older people may be more sensitive to caffeine and thus more likely to have certain side effects, such as irritability, nervousness, anxiety, and sleep problems.


Anyone with allergies to foods, dyes, preservatives, or to the compounds aminophylline, dyphylline, oxtriphylline, theobromine, or theophylline should check with a physician before using caffeine. Anyone who has ever had an unusual reaction to caffeine should also check with a physician before using it again.

Other medical conditions

Caffeine may cause problems for people with these medical conditions:

  • peptic ulcer
  • heart arrhythmias or palpitations
  • heart disease or recent heart attack (within a few weeks)
  • high blood pressure
  • liver disease
  • insomnia (trouble sleeping)
  • anxiety or panic attacks
  • agoraphobia (fear of being in open places)
  • premenstrual syndrome (PMS)

Recommended intakes

Generally, taking 400 mg per day of caffeine is considered safe. Caffeine consumption at this level in adults has not shown to increase the risk of cancer, cardiovascular disease, and early end of pregnancy. People who do not already consume caffeine are not advised to incorporate caffeine into their diets.

Caffeine content of common dietary and medicinal sources

Caffeine content of common dietary and medicinal sources

It is recommended to avoid taking too much caffeine when it is taken as an over-the-counter drug. It is important to consider how much caffeine is being taken in from coffee, tea, chocolate, soft drinks, and other foods that contain caffeine. Individuals should check with a pharmacist or healthcare professional to find out how much caffeine is safe to use.

The FDA advises against combining alcohol and caffeine, since doing so can result in higher alcohol consumption and increased risk of negative effects of Page 637  |  Top of Articlealcohol. Caffeine does not affect alcohol levels in blood. Using caffeine and alcohol together can lead to an upset stomach, nausea, and vomiting.

Caffeine can pass from a pregnant woman's body into the developing fetus. It is recommended to restrict the amount of caffeine to 200 mg per day during pregnancy. Some studies showed that giving laboratory animals very large doses of caffeine (equal to human doses of 12–24 cups of coffee a day) resulted in birth defects. In humans, evidence exists that doses of more than 300 mg of caffeine a day (about the amount of caffeine in two or three cups of coffee) may cause miscarriage or problems with the baby's heart rhythm. Women who take more than 300 mg of caffeine a day during pregnancy are also more likely to have babies with low birth weights. Any woman who is pregnant or planning to become pregnant should check with her physician before using caffeine.

Caffeine passes into breast milk and can affect the nursing baby, causing irritability and trouble sleeping. Women who are breastfeeding should check with their physicians before using caffeine.

Intake sources

Caffeine is found naturally in coffee, cocoa, kola seed kernels or nuts (Cola nitida), and a variety of teas. Other foods and beverages, such as chocolate, soft drinks, and energy drinks, also contain caffeine. Caffeine medication can be purchased in over-the-counter tablet and capsule form (No Doz, Overtime, Pep-Back, Quick-Pep, and Vivarin). Some prescription pain relievers, medicines for migraine headaches, and antihistamines also contain caffeine.

Caffeine containing drinks have varying amounts of caffeine: energy drinks (3–35 mg/fl oz), brewed coffee (12 mg/fl oz), instant coffee (8 mg/fl oz), espresso (64 mg/fl oz), black tea (6 mg/fl oz), green tea (2–5 mg/fl oz), soda that contain caffeine (1–4 mg/fl oz).

Role in population health

Caffeine has several desired effects for some individuals, such as increase in alertness. Caffeine helps several medications to work better and alone can relieve some headaches. It is used in healthcare to treat certain medical problems. However, some individuals should limit or avoid the consumption of caffeine. Several side effects can also occur with moderate or high levels of caffeine intake.

Side effects

At recommended doses, caffeine can cause restlessness, irritability, nervousness, shakiness, headache, lightheadedness, sleeplessness, nausea, vomiting, and upset stomach. At higher than recommended doses, caffeine can cause excitement, agitation, anxiety, confusion, a sensation of light flashing before the eyes, unusual sensitivity to touch, unusual sensitivity of other senses, ringing in the ears, frequent urination, muscle twitches or tremors, heart arrhythmias, rapid heartbeat, flushing, and convulsions.


Using caffeine with certain other drugs may interfere with the effects of the drugs or cause unwanted—and possibly serious—side effects. Certain drugs interfere with the breakdown of caffeine in the body. These include oral contraceptives that contain estrogen, the antiarrhythmic drug mexiletine (Mexitil), the ulcer drug cimetidine (Tagamet), and the drug disulfiram (Antabuse), used to treat alcoholism.

Caffeine interferes with drugs that regulate heart rhythm, such as quinidine and propranolol (Inderal). Caffeine may also interfere with the body's absorption of iron. Anyone who takes iron supplements should take them at least an hour before or two hours after using caffeine.

Serious side effects are possible when caffeine is combined with certain drugs. For example, taking caffeine with the decongestant phenylpropanolamine can raise blood pressure. Very serious heart problems may occur if caffeine and monoamine oxidase inhibitors (MAO) are taken together. These drugs are used to treat Parkinson's disease, depression, and other psychiatric conditions. Consult with a pharmacist or physician about which drugs can interact with caffeine.

Because caffeine stimulates the nervous system, anyone taking other central nervous system stimulants should be careful about using caffeine.

Legislation and regulation

Foods and beverages that have caffeine added are required to have caffeine listed in the ingredient section of a food label. Caffeine added to foods and beverages is considered safe at the levels of 0.02%. Foods that naturally contain caffeine will not have caffeine listed on the food label, since caffeine is not a nutrient and, in that case, is not an added substance. The FDA does not require companies to specify on the nutrition label the exact amount of caffeine added to foods and beverages. However, some companies voluntarily include the amount of caffeine on the label. Many products with added caffeine also contain cautionary statements and advise against the use in children, pregnant women or people with sensitivity to caffeine.

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U.S. Food and Drug Administration. “Why Isn't the Amount of Caffeine a Product Contains Required on a Food Label?” (accessed April 14, 2017).


Office of Dietary Supplements. National Institutes of Health, 6100 Executive Blvd., Room 3B01, MSC 7517, Bethesda, MD 20892-7517, (301) 435-2920,, .

Paula Ford-Martin
Revised by Ielyzaveta Shkoda, RDN, CNSC, FAND

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

Source Citation

Source Citation   (MLA 8th Edition)
Ford-Martin, Paula, and Ielyzaveta Shkoda, RDN, CNSC, FAND. "Caffeine." The Gale Encyclopedia of Nursing and Allied Health, edited by Jacqueline L. Longe, 4th ed., vol. 2, Gale, 2018, pp. 635-638. Gale Health and Wellness, Accessed 14 Dec. 2019.

Gale Document Number: GALE|CX3662600188