Caffeine Toxicity Clinical Presentation

Updated: Aug 21, 2018
  • Author: David Yew, MD; Chief Editor: Michael A Miller, MD  more...
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If acute caffeine ingestion is suspected, patients or their family members should be questioned about their use of prescription medications, over-the-counter (OTC) drugs, and illicit drugs. Patients and family members should be queried about the use of any of the following drugs:

  • Cocaine
  • Amphetamines
  • Methamphetamine
  • Phencyclidine (PCP)
  • Antidepressants
  • Asthma medications
  • Thyroid medications
  • Anticholinergics (eg, OTC allergy medications)

The patient and family members or friends may be able to give a history of recent caffeine ingestion (eg, 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 central nervous system (CNS), cardiovascular, and gastrointestinal (GI) hyperstimulation.

CNS features include the following:

  • Headache

  • Lightheadedness

  • Anxiety, agitation

  • Tremulousness, perioral and extremity tingling (resulting from tachypnea-induced respiratory alkalosis)

  • Confusion, psychosis

  • Seizures

Cardiovascular features include the following:

  • Palpitations or racing heart rate

  • Chest pain

GI features include the following:

  • Nausea and vomiting

  • Abdominal pain

  • Diarrhea, bowel incontinence

  • Anorexia



Vital signs may include tachypnea and tachycardia. On blood pressure measurement, a characteristic finding is widened pulse pressure due to the positive inotropic effect as well as the vasodilatory effect of caffeine. Hypotension may be present.

CNS findings on physical examination include the following:

  • Anxiety, agitation

  • Tremors

  • Seizures

  • Altered mental status

The pupils are dilated but reactive to light. The thyroid should be examined because thyrotoxicosis may mimic caffeine toxicity.

GI findings include the following:

  • 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, [21] or energy drinks (eg, Red Bull, AMP Energy Drink, Rockstar, Monster) or take caffeine in herbal preparations [22] .

Considerations include the following:

  • Acute toxicity can occur after intentional or unintentional ingestion. OTC alertness-promoting medications are often implicated in intentional overdoses.

  • Certain medications, such as cytochrome inhibitors (eg, cimetidine) and oral contraceptives, impair caffeine metabolism. [23]

  • Caffeine clearance is reduced in patients with chronic liver disease, in pregnant women, and in infants.

  • Caffeine clearance is increased in smokers. With smoking cessation, serum caffeine concentrations can double even if caffeine consumption remains stable.