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Possible side effects of caffeine

by — Last updated: 2013-11-19 in Healthy Living

Table of Contents

Around 90 percent of Americans consume caffeine in some form every single day. And more than half of all American adults consume more than 300 mg of caffeine every day, making it America's most popular drug by far.

Lethal dose

The minimum lethal dose of caffeine ever reported is 3,200 mg, administered intravenously. Although achieving lethal dose with coffee would be exceptionally difficult, there have been many reported deaths from intentional overdosing on caffeine pills.

Physical and mental disorders

There are 4 caffeine-induced psychiatric disorders and they include:

  • caffeine intoxication
  • caffeine-induced anxiety disorder
  • caffeine-induced sleep disorder  
  • caffeine-related disorder not otherwise specified


Symptoms of caffeine intoxication include:

  • restlessness
  • nervousness
  • excitement
  • insomnia
  • flushed face
  • diuresis
  • muscle twitching
  • rambling flow of thought and speech
  • paranoia
  • cardiac arrhythmia or tachycardia
  • psychomotor agitation
  • gastrointestinal complaints
  • increased blood pressure
  • rapid pulse
  • vasoconstriction
  • increased amounts of fatty acids in the blood
  • increased production of gastric acid


In extreme cases:

  • mania
  • depression
  • lapses in judgment
  • disorientation
  • loss of social inhibition
  • delusions
  • hallucinations
  • psychosis

Because caffeine increases the production of stomach acid, high usage over time can lead to peptic ulcers, erosive esophagitis, and gastro-esophageal reflux disease.

Caffeine withdrawal symptoms

The most important proof that caffeine is addictive is presence of caffeine withdrawal symptoms. It is proven that regular caffeine consumption reduces sensitivity to caffeine. When caffeine intake is reduced, the body becomes oversensitive to adenosine which leads to sensitiveness, blood pressure drop, excess of blood in the head and headache.

This headache, well known among coffee drinkers, usually lasts from one to five days, and can be alleviated with analgesics such as Aspirin.

Often, people who are reducing caffeine intake report:

  • being irritable
  • unable to work
  • nervous
  • restless
  • feeling sleepy
  • having a headache
  • nausea and vomiting in extreme cases
  • drowsiness
  • feeling hot and cold
  • apathy
  • inability to concentrate
  • constipation         
  • runny nose

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