Caffeine overdose: Symptoms, treatment, and how much is too much?

In this article, we look at official advice on how much caffeine people can consume, sources of caffeine, and treatment and prevention of an overdose.

We also examine what caffeine is and the risk factors, likelihood, and symptoms of a caffeine overdose.

What is caffeine

Caffeine occurs naturally in certain plants, nuts, and seeds and manufacturers add it to some foods and drinks.

Caffeine has a range of effects on the body, from suppressing appetite to making a person feel more awake.

Caffeine is a stimulant, meaning that it increases some of the body’s processes. For example, messages sent between the brain and the body can travel faster. This is one reason why a person may feel more alert or focused after consuming caffeine.

Heart rate and breathing may also speed up after someone consumes caffeine. Most of the effects on the body are short term and do not cause lasting harm. But if a person consumes a large amount of caffeine, it can have a harmful effect on the body.

How likely is a caffeine overdose?

It is relatively easy for someone to consume too much caffeine and to have side effects. But a life-threatening overdose is rare. And caffeine overdose as a cause of death is even rarer.

In a 2018 review of scientific journal articles, researchers identified 92 reported deaths from caffeine overdose. This review included all journals since online databases began. The researchers believe that around one-third of these deaths are likely to be suicide.

In general, caffeine will begin to affect the body if there are more than 15 milligrams per liter (mg/L) in the blood. A concentration of 80 to 100 mg/L can be fatal.

Caffeine overdose is most likely to result from taking a dietary supplement or caffeine tablets rather than from drinking coffee, especially when people combine these products with energy drinks, sodas, or coffee. This risk is because there is a higher level of caffeine in many of these supplements than in usual foods and drinks.

Unlike drinking coffee, or even taking supplements containing caffeine, using purified caffeine powder is highly dangerous and is much more likely to cause an overdose.

The United States Food and Drug Administration (FDA) warn that a teaspoon of powdered caffeine can be equivalent to 28 cups of coffee. It stresses that pure and highly concentrated caffeine products can have serious health consequences.

The cause of death from caffeine overdose is typically ventricular fibrillation. This condition happens when the lower chambers of the heart vibrate rather than contracting regularly. Ventricular fibrillation stops the heart from beating normally and causes cardiac arrest.

The typical side effects of caffeine can include:

  • feeling more awake or alert
  • feeling restless, anxious, or irritable
  • increased body temperature
  • dehydration
  • headache
  • faster breathing
  • faster heart rate

Symptoms of a caffeine overdose can include:

  • very fast or irregular heartbeat
  • shakiness
  • feeling sick or vomiting
  • confusion
  • panic attack

If a person experiences any of the symptoms of caffeine overdose, they should seek medical advice.

The half-life of a drug is how long it takes for half the drug to leave the body. The half-life of caffeine is 3 to 5 hours.

A person may experience side effects that are unpleasant but not a cause for concern, such as feeling restless or dehydrated. These side effects will usually go away within 3 to 5 hours.

In the case of mild side effects, a person can take the following steps at home:

  • not drinking any further caffeine
  • drinking water to rehydrate
  • taking a walk to use energy and stop feeling restless

A person who has a caffeine overdose may need medical treatment, including intravenous fluids, supplements, or activated charcoal.

Activated charcoal can stop caffeine from entering the gut. If caffeine does enter the gut, an even higher level could get into the blood and cause further health problems.


Regularly consuming high doses of caffeine may cause long-term health problems, including:

  • stomach ulcers
  • difficulty sleeping
  • anxiety and depression

For most people, their caffeine consumption is unlikely to lead to an overdose or long-term health problems. People who consume caffeine regularly develop a tolerance to some of its side effects. Drinking coffee in moderation may also have health benefits.

Being aware of the amount of caffeine found in food, drink, and supplements can help. So a person may choose to have a smaller-sized coffee, alternate regular with decaffeinated coffee, or decaffeinated hot drinks such as herbal teas.

People should always be aware and remember that caffeine powder and supplements can contain very high levels of caffeine that may be harmful to health. The FDA strongly advise people to avoid these products.

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