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Caffeine Toxicity Clinical Presentation

  • Author: David Yew, MD; Chief Editor: Asim Tarabar, MD  more...
Updated: Mar 31, 2014


If acute caffeine ingestion is suspected, patients or their family members should be questioned about their use of prescription medications, OTC drugs, and illicit drugs. Patients and family members should be queried about the use of cocaine, amphetamines, methamphetamine, phencyclidine (PCP), antidepressants, asthma medications, thyroid medications, or anticholinergics (eg, OTC allergy medications).

The patient and his or her family members or friends may be able to give a history of recent caffeine ingestion (ingestion of alertness-promoting OTC medications, caffeinated beverages, or diet medications) or a history of recent behavior compatible with such use (eg, the patient was trying to lose weight or taking stimulants to aid in working or studying). In an acute overdose, pill bottles found at the scene may provide a clue to what the patient ingested.

When ingested chronically in excessive amounts, caffeine produces a specific toxidrome (caffeinism), which consists of primarily CNS, cardiovascular, and GI hyperstimulation.

  • CNS features
    • Headache
    • Lightheadedness
    • Anxiety, agitation
    • Tremulousness, perioral and extremity tingling (resulting from tachypnea-induced respiratory alkalosis)
    • Confusion, psychosis
    • Seizures
  • Cardiovascular features
    • Palpitations or racing heart rate
    • Chest pain
  • GI features
    • Nausea and vomiting
    • Abdominal pain
    • Diarrhea, bowel incontinence
    • Anorexia


See the list below:

  • CNS findings
    • Anxiety, agitation
    • Tremors
    • Seizures
    • Altered mental status
  • Head, eyes, ears, nose, and throat findings
    • The pupils are dilated but reactive to light.
    • The thyroid should be examined because thyrotoxicosis may mimic caffeine toxicity.
  • Cardiovascular findings
    • Characteristic finding is widened pulse pressure due to positive inotropic effect as well as vasodilatory effect of caffeine.
    • Sinus tachycardia, dysrhythmias (eg, premature ventricular contractions, supraventricular tachycardias [SVTs], ventricular rhythms)
    • Hypotension
  • Respiratory finding - Tachypnea
  • GI findings
    • Vomiting
    • Abdominal cramping
    • Hyperactive bowel sounds


Chronic toxicity is generally encountered in people who have ingested higher doses of caffeine-containing compounds (alone or in combination) for various reasons. Patients may be unaware that some products contain caffeine or that high doses of caffeine can be harmful. Patients may ingest caffeine-containing analgesics for headaches, OTC caffeine-containing medications for dieting, or OTC medications for improving alertness while studying or working. In addition, people may drink caffeine in beverages such as coffee, tea, soft drinks,[15] or energy drinks (eg, Red Bull, AMP Energy Drink, Rockstar, Monster) or take caffeine in herbal preparations[16] .

  • Acute toxicity can occur after intentional or unintentional ingestion. OTC alertness-promoting medications are often implicated in intentional overdoses.
  • Certain medications, such as CYP inhibitors (eg, cimetidine) and oral contraceptives, impair caffeine metabolism.
  • Caffeine clearance is reduced in patients with chronic liver disease, in pregnant women, and in infants.
  • Caffeine clearance is increased in smokers. With a stable amount of ingestion, serum caffeine concentrations can double in patients who stop smoking.
Contributor Information and Disclosures

David Yew, MD Assistant Clinical Professor, Department of Surgery, University of Hawaii, John A Burns School of Medicine; Medical Director and Flight Physician, Hawaii Life Flight, AirMed International

David Yew, MD is a member of the following medical societies: American College of Emergency Physicians, Air Medical Physician Association

Disclosure: Nothing to disclose.


China N Byrns Department of Cell and Molecular Biology, University of Hawaii at Manoa

China N Byrns is a member of the following medical societies: Phi Beta Kappa

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

John G Benitez, MD, MPH Associate Professor, Department of Medicine, Medical Toxicology, Vanderbilt University Medical Center; Managing Director, Tennessee Poison Center

John G Benitez, MD, MPH is a member of the following medical societies: American Academy of Clinical Toxicology, American Academy of Emergency Medicine, American College of Medical Toxicology, American College of Preventive Medicine, Undersea and Hyperbaric Medical Society, Wilderness Medical Society, American College of Occupational and Environmental Medicine

Disclosure: Nothing to disclose.

Chief Editor

Asim Tarabar, MD Assistant Professor, Director, Medical Toxicology, Department of Emergency Medicine, Yale University School of Medicine; Consulting Staff, Department of Emergency Medicine, Yale-New Haven Hospital

Disclosure: Nothing to disclose.

Additional Contributors

James E Keany, MD, FACEP Associate Medical Director, Emergency Services, Mission Hospital Regional Medical Center, Children's Hospital of Orange County at Mission

James E Keany, MD, FACEP is a member of the following medical societies: American College of Emergency Physicians, American College of Sports Medicine, California Medical Association

Disclosure: Nothing to disclose.


Jeffrey T Laczek, MD Gastroentology Fellow, Walter Reed Army Medical Center

Disclosure: Nothing to disclose.

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Caffeine content of various foods, beverages, medications, and supplements. Caffeine content is approximate for brewed beverages and chocolate).
Chemical structure of caffeine.
Table 1. Reported Caffeine Content of Common Items[3]
ItemAmountCaffeine Content, mg
M & M Milk Chocolate Candies47.9 g (1 bag)7
Coca-Cola Classic12 oz35
Fiorinal/Fioricet1 tablet40
Brewed black tea, generic8 oz45-74
Red Bull Regular8.4 oz80
Brewed coffee, generic8 oz57
Midol1 Gel Cap60
No Doz1 tablet100
Regular 5-Hour Energy2 oz138
Rockstar16 oz160
Monster Energy16 oz160
Espresso, generic1 oz170
Vivarin1 tablet200
Starbucks Tall Americano16330
Table 2. Caffeine-Related Poisonings Reported to the NPDS From 2009-2011
CategorySingle ExposuresDeaths
Energy Drinks      
Caffeine containing-139548-01
Caffeine only-1691062-00
Ethanol and caffeine containing-76131-00
Ethanol and caffeine only-23-00
Pheylnolamine and caffeine combinations (diet aid)102211000
Table 3. Energy Drink Exposure
ItemNo. Exposures (single)Exposures (5)Exposures (6-12)Exposures (12-19)Exposures (20)
Energy Drinks     
Caffeine containing54822760141111
Caffeine only106258291128226
Ethanol and caffeine containing1311557828
Ethanol and caffeine pnly31002
Pheylnolamine and caffeine combinations (diet aid)115114
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