Caffeine Side Effects

Medically reviewed by Drugs.com. Last updated on Oct 28, 2024.

Applies to caffeine: solution.

Other dosage forms:

• oral solution, oral tablet
• intravenous solution

Precautions

Caffeine powder and tablets are for occasional use only. They are not intended to replace sleep and should not be used regularly for this purpose. If unusual tiredness or weakness or drowsiness continues or returns often, check with your doctor.

Before you have any medical tests, tell the doctor in charge that you are taking this medicine. The results of some tests on the heart may be affected by this medicine.

The recommended dose of this medicine contains about the same amount of caffeine as a cup of coffee. Do not drink large amounts of caffeine-containing coffee, tea, or soft drinks while you are taking this medicine. Also, do not take large amounts of other medicines that contain caffeine. To do so may cause unwanted effects.

The amount of caffeine in some common foods and beverages is as follows:

• Coffee, brewed—40 to 180 milligrams (mg) per cup.
• Coffee, instant—30 to 120 mg per cup.
• Coffee, decaffeinated—3 to 5 mg per cup.
• Tea, brewed American—20 to 90 mg per cup.
• Tea, brewed imported—25 to 110 mg per cup.
• Tea, instant—28 mg per cup.
• Tea, canned iced—22 to 36 mg per 12 ounces.
• Cola and other soft drinks, caffeine-containing—36 to 90 mg per 12 ounces.
• Cola and other soft drinks, decaffeinated—0 mg per 12 ounces.
• Cocoa—4 mg per cup.
• Chocolate, milk—3 to 6 mg per ounce.
• Chocolate, bittersweet—25 mg per ounce.

Caffeine may cause nervousness or irritability, trouble in sleeping, dizziness, or a fast or pounding heartbeat. If these effects occur, discontinue the use of caffeine-containing beverages and medicines, and do not eat large amounts of chocolate-containing products.

To prevent trouble in sleeping, do not take caffeine-containing beverages or medicines too close to bedtime.

Serious side effects of caffeine

Along with its needed effects, caffeine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor as soon as possible if any of the following side effects occur while taking caffeine:

Symptoms of overdose

• abdominal or stomach pain
• agitation, anxiety, excitement, or restlessness
• confusion or delirium
• convulsions (seizures)—in acute overdose
• dehydration
• faster breathing rate
• fast or irregular heartbeat
• fever
• frequent urination
• headache
• increased sensitivity to touch or pain
• irritability
• muscle trembling or twitching
• nausea and vomiting, sometimes with blood
• overextending the body with head and heels bent backward and body bowed forward
• painful, swollen abdomen or vomiting (in newborn babies)
• ringing or other sounds in ears
• seeing flashes of "zig-zag" lights
• whole-body tremors (in newborn babies)

Other side effects of caffeine

Some side effects of caffeine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

After you stop using this medicine, your body may need time to adjust. The length of time this takes depends on the amount of medicine you were using and how long you used it. During this time, check with your doctor if you notice any of the following side effects:

For healthcare professionals

Applies to caffeine: compounding powder, intravenous solution, oral gum, oral liquid, oral tablet, oral tablet dispersible, oral tablet extended release.

General adverse events

Long-term follow-up studies have not shown caffeine to adversely affect neurological development or growth parameters.^[Ref]

Gastrointestinal

• Very common (10% or more): Constipation (up to 17.4%)
• Common (1% to 10%): Necrotizing enterocolitis, gastritis, GI hemorrhage, gastroesophageal reflux, dilated bowel loops
• Frequency not reported: Increased gastric aspirate, GI intolerance, vomiting, regurgitation^[Ref]

Cardiovascular

• Common (1% to 10%): Hemorrhage, tachycardia
• Uncommon (0.1% to 1%): Arrhythmia
• Frequency not reported: Increased left ventricular output, increased stroke volume, hypertension^[Ref]

Dermatologic

• Common (1% to 10%): Rash, dry skin, skin breakdown^[Ref]

Hematologic

• Common (1% to 10%): Disseminated intravascular coagulation, anemia
• Frequency not reported: Decreased hemoglobin^[Ref]

Hepatic

• Common (1% to 10%): Kidney failure^[Ref]

Metabolic

• Common (1% to 10%): Acidosis, hyperglycemia
• Frequency not reported: Hypoglycemia, temporary reduced weight gain, decreased thyroxine^[Ref]

Nervous system

• Common (1% to 10%): Cerebral hemorrhage
• Uncommon (0.1% to 1%): Convulsions/seizures
• Frequency not reported: Irritability, restlessness, jitteriness, tremors, brain injury^[Ref]

Ocular

• Common (1% to 10%): Retinopathy of prematurity^[Ref]

Other

• Common (1% to 10%): Perinatal disorder (trace aspirates, feeding intolerances), injection site reaction, sepsis, accidental injury, abnormal healing, infusion site phlebitis and inflammation
• Frequency not reported: Failure to thrive, deafness^[Ref]

Respiratory

• Common (1% to 10%): Dyspnea, lung edema
• Frequency not reported: Tachypnea^[Ref]

Hypersensitivity

• Rare (less than 0.1%): Hypersensitivity reaction^[Ref]

Renal

• Frequency not reported: Increased urine flow rate, increased creatinine clearance, increased sodium and calcium excretion^[Ref]

See also:

Frequently asked questions

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• Does caffeine affect Vraylar (cariprazine)?
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• Does caffeine help migraines?
• Does caffeine cause high blood pressure?
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Further information

Caffeine side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

Medical Disclaimer