Caffeine toxicity, also known as caffeine overdose, is a state of intoxication caused by excessive caffeine. This intoxication covers a variety of unpleasant physical and mental symptoms associated with the consumption of excessive amounts of caffeine.

Caffeine is considered one of the most widely consumed drugs around the world. Around 80% of the world population consumes caffeine in one form or another. It is found in coffee, tea, caffeinated alcoholic drinks, cocoa, chocolate, soft drinks, especially cola, and is an important component of energy drinks and other dietary supplements.

Caffeinism usually occurs when consumption of caffeine reaches per day. For reference, a brewed 8oz (227ml) cup of coffee contains ~95 mg of caffeine (per USDA).

According to the Diagnostic and Statistical Manual of Mental Disorders, caffeine overdose can result in a state of excessive stimulation of the central nervous system and the essential feature of caffeine intoxication is the recent consumption of caffeine. This diagnosis requires the presence of at least five signs or symptoms, from a list of 12, that develop during or shortly after caffeine use. This syndrome regularly happens when a person ingested large amounts of caffeine from any source (e.g., more than 400–500 mg at a time).

The signs and symptoms are divided into one group that can appear after an intake of as little as 100 mg of caffeine (roughly the amount contained in a cup of brewed coffee) and another group of symptoms that appear at higher levels of intake (more than 1 g per day). Low-dose symptoms include:

  • restlessness
  • nervousness
  • excitement
  • insomnia
  • flushed face
  • diuresis (increased urination)
  • gastrointestinal disturbance

Symptoms associated with high doses include:

  • muscle twitching
  • rambling flow of thought and speech
  • tachycardia and cardiac arrhythmia,
  • periods of inexhaustibility
  • psychomotor agitation In cases of much larger overdoses, mania, depression, lapses in judgment, disorientation, disinhibition, delusions, weight loss, loss of appetite, hallucinations, or psychosis may occur.

Death can occur as a result of caffeine overdose. The LD<sub>50</sub> of caffeine in humans is dependent on individual sensitivity, but is estimated to be 150–200 milligrams per kilogram of body mass ( of coffee for a 70 kilogram adult). A number of fatalities have been caused by overdoses of readily available powdered caffeine supplements, for which the estimated lethal amount is less than a tablespoon. The lethal dose is lower in individuals whose ability to metabolize caffeine is impaired due to genetics or chronic liver disease. A death was reported in a man with liver cirrhosis who overdosed on caffeinated mints.

Treatment

Treatment of mild caffeine intoxication is directed toward symptom relief; severe intoxication may require peritoneal dialysis, hemodialysis, or hemofiltration.

There is no standard value for "a cup of coffee". The caffeine content of cola drinks and most energy drinks can be difficult to determine, because in many cases the labels do not indicate the dose per serving. Caffeine doses in these beverages range from 20 to 30&nbsp;mg in some soft drinks, up to 350&nbsp;mg or more in some energy drinks. Although some websites report caffeine content for beverages, official lists are not available and the number of brands continually grows.