Caffeine side effects

caffeine side effectsCaffeine Side Effects


Caffeine is the most spread substance which stimulates the central nervous system and is consumed both as a component of coffee and tea, as an additive to various beverages and foods, and as a medicine. It was estimated that about 80% of the world’s population consume caffeine every day. Despite its obvious benefits caffeine side effects may cause a lot of adverse effects and be even life-threatening if consumed excessively.

According to the researches 5 grams of caffeine (equivalent to 30-40 cups of regular coffee) may cause the death of the consumer.


Necrotizing enterocolitis

The most frequently reported side effect is necrotizing enterocolitis.The condition affects children, which were prematurely born and experienced breathing problems that required the administration of caffeine as a central nervous system stimulator.


Physical side effects

Caffeine affects the circulatory system by causing vasoconstriction and increasing the level of catecholamines (adrenalin and noradrenalin) in the blood. This results in high blood pressure and tachycardia.The functioning of gastrointestinal system may be also be impaired. Caffeine increases dieresis and natriuresis.

The common side effects include the following:

  • black, tarry stools, blood in the urine;
  • bruising;
  • coughing or vomiting blood;
  • fast heartbeat and increased blood pressure;
  • fever, chills;
  • headache, lightheadedness, fainting;
  • indigestion, feeding intolerance, nausea, vomiting, severe stomach pain;
  • muscle twitching, jitters, shakiness, cramps, seizures;
  • rapid, shallow breathing;
  • tolerance to caffeine side effects increases the risk of overdose;

Related: Caffeine tolerance

Central nervous system and behavior side effects

As long as caffeine influences the neurotransmitters found in the brain, caffeine side effects consumption is affecting the nervous system, behavior and psychological aspects of life.

These side effects include:

  • seizures;
  • headache (especially as a withdrawal symptom);
  • disorientation;
  • nervousness;
  • agitation;
  • irritability;
  • anxiety;
  • confusion;
  • stupor/coma;
  • insomnia and other sleeping difficulties;
  • dependency;



Consumption of more than 400-500 mg of caffeine side effectsper day is likely result in caffeine intoxication.Overdose symptoms include:

  • Central nervous system symptoms: nervousness, anxiety, irritability, insomnia, confusion, restlessness, agitation, headache and/or delirium;
  • Vision and hearing symptoms;
  • Skin sensitivity (to touch or pain);
  • Circulatory system: tachycardia, arrhytmia and high blood pressure;
  • Muscular involvement: seizures, trembling and overextension;
  • Respiratory system: tachypnoe (increased breathing rate);
  • Gastrointestinal tract: abdominal pain, nausea and vomiting;
  • Urinary system: frequent urination;
  • Other symptoms: flushing, fever and dehydration.


Caffeine tolerance test

Caffeine tolerance test