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Dr Karen Martin
Reviewed by Dr Karen MartinReviewed on 19.10.2023 | 2 minutes read

Caffeine is a stimulant drug naturally found in many plants, such as coffee, cocoa, and tea. It reduces tiredness and increases alertness by blocking a chemical produced by the body to signal fatigue.

Who is it for?

People over the age of 16 years can use caffeine to increase alertness, reduce fatigue and malaise, and enhance pain relief when used with acetaminophen.

How does it work?

Caffeine works by blocking the actions of adenosine, a natural chemical the body produces to signal tiredness. It is often included in many over-the-counter cold and flu remedies due to its effects of reducing fatigue caused by cold or flu, and in combination with other medications such as pain relief. It can be purchased in tablet form either as synthetic caffeine or as guarana (plant-based caffeine).

Should anyone avoid taking it?

Caffeine should not be used by children under 12 years when it is found in cold, flu, or pain relief products. Caffeine alone is not recommended for use by anyone under 16 years. Caffeine should also be used with caution in those taking stimulant attention deficit hyperactivity disorder (ADHD) medication as it can increase the side effects of their medication.

Are there any side effects?

As with any medication, some people are bound to get some unwanted side effects. Some of the common ones include insomnia, anxiety, irritability, nausea, headaches, and diarrhea.

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This article has been written by UK-based doctors and pharmacists, so some advice may not apply to US users and some suggested treatments may not be available. For more information, please see our T&Cs.
Dr Karen Martin
Reviewed by Dr Karen Martin
Reviewed on 19.10.2023
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