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Caffeine facts

What is caffeine?

Effects of caffeine


Further information


pdficon small Download the Caffeine fact sheet [PDF:455KB]

Please note: The information given on this page is not medical advice and should not be relied on in this way. Individuals wanting medical advice on this issue should consult a health professional.

What is caffeine?

Caffeine is a stimulant drug, which means it speeds up the messages travelling between the brain and the body.

It's found in the seeds, nuts and leaves of a number of different plants, including:

  • Coffea Arabica (used for coffee)
  • Camelia sinensis (used for tea)
  • Cola acuminate (used as a nut, tea or in soft drinks including cola)
  • Theobroma cacao (used in cocoa and chocolate)
  • Paulinia cupana (used as guarana in snack bars and energy drinks)1


How is caffeine used?

Caffeine is used in a number of different products. The amount of caffeine in these products can vary dramatically, so it's always best to check the label, but the average amounts are listed below.

Product Average caffeine content
(mg/100 ml)
Red Bull® 32.0
Mountain Dew® 15.0
Coca Cola® 9.7*
Diet Coke® 9.7*
Coke Zero® 9.6*
Brewed black tea 22.5
Brewed green tea 12.1
Coffee, cappuccino 101.9
Coffee, flat white 86.9
Coffee, long black 74.7
Coffee, from ground coffee beans, espresso style 194.0
Chocolate, milk with added milk solids 20.0
Chocolate, dark, high cocoa solids 59.0

Adapted from Food Regulation Standing Committee, Caffeine Working Group. (2013). The regulation of caffeine in foods.
*The Cocoa-Cola Company. (2015). Caffeine: Your questions answered.

Effects of caffeine

There is no safe level of drug use. Use of any drug always carries some risk. It's important to be careful when taking any type of drug.

Caffeine affects everyone differently, based on:

  • Size, weight and health
  • Whether the person is used to taking it
  • Whether other drugs are taken around the same time
  • The amount taken


The following effects may be experienced between 5 to 30 minutes after consuming caffeine, and may continue for up to 12 hours:

  • Feeling more alert and active
  • Restlessness, excitability and dizziness
  • Anxiety and irritability
  • Dehydration and needing to urinate more often
  • Higher body temperature
  • Faster breathing and heart rate
  • Headache and lack of concentration
  • Stomach pains3


Children and young people who consume energy drinks containing caffeine may also suffer from sleep problems, bed-wetting and anxiety.4


If a large amount of caffeine is consumed it could also cause an overdose. If any of the following effects are experienced an ambulance should be called straight away by dialling triple zero (000).

  • Tremors
  • Nausea and vomiting
  • Very fast and irregular heart rate
  • Confusion and panic attack
  • Seizures5


It is possible to die from having too much caffeine, but this is extremely rare. This would usually only happen if 5–10 grams of caffeine (or 80 cups of strong coffee) were consumed one after the other.1

In small children, caffeine poisoning can happen if a lower amount, such as around 1 gram of caffeine (equal to around 12 energy drinks) is consumed one after the other.6

Coming down

Some people consume drinks with caffeine so that they can continue working or studying at night. However, the after-effect is that they will feel tired and lethargic the next day.

Long-term effects

Regular, heavy use of caffeine (such as more than 4 cups of coffee a day) may eventually cause:

  • Osteoporosis
  • High blood pressure and heart disease
  • Heartburn
  • Ulcers
  • Difficulty sleeping
  • Infertility (in men and women)
  • Anxiety
  • Depression
  • Needing to use more to get the same effect
  • Dependence on caffeine1


Using caffeine with other drugs

The effects of taking caffeine with other drugs – including over-the-counter or prescribed medications – can be unpredictable and dangerous, and could cause:

Caffeine + alcohol: enormous strain on the body, and can mask some effects of alcohol such as falling asleep, leading to drinking more and risk taking behaviour.

Caffeine + other stimulant drugs: increase the risk of cardiovascular problems.7


Giving up caffeine after using it for a long time is challenging because the body has to get used to functioning without it. Withdrawal symptoms usually start within 24 hours after the last dose – or even within 6 hours for people who consume a lot of caffeine regularly. The symptoms can last for around 36 hours, or even longer for people who consume a lot.

These symptoms can include:

  • Headache
  • Tiredness
  • Sweating
  • Muscle pains
  • Anxiety and tension8


Further information


Reducing the risks



ADF SEARCH—Find further credible research and information on caffeine. 

ADIN– Find other credible websites and apps on caffeine.


1. Brands, B., Sproule, B., & Marshman, J. (Eds.). (1998). Drugs & drug abuse (3rd ed.). Ontario: Addiction Research Foundation.

2. Food Standards Australia New Zealand. (2014). Caffeine.

3. Upfal, J. (2006). The Australian drug guide. (7th ed.). Melbourne: Black Inc.

4. Seifer, S., Schaechter, J., Hershorin, E. & Lepshultz, S. (2011). Health effects of energy drinks on children, adolescents, and young adults. Pediatrics, 127(3). 511–528.

5. NPS Medicinewise. (2013). What's the buzz with energy drinks?

6. Nawrot, P., Jordan, S., Eastwood, J., Rotstein, J., Hugenholtz, A. & Feeley, M. (2003). Effects of caffeine on human health. Food Additives and Contaminants, 20(1). 1–30.

7. Arria, A., Calderia, K., Kasperski, S., O'Grady, K., Vincent, K., Griffiths, R. & Wish, E. (2010). Increased alcohol consumption, nonmedical prescription drug use, and illicit drug use are associated with energy drink consumption among college students. Journal of Addiction Medicine, 4(2). 74–80.

8. American Psychiatric Association. (2013). Diagnostic and Statistical Manual of Mental Disorders. (5th ed). Washington: American Psychiatric Publishing.

Last updated: 5 May 2016


Information you heard is intended as a general guide only. This audio is copyrighted by the Australian Drug Foundation. Visit for more