Caffeine is a drug which comes from the leaves, beans or nuts of different plants. Caffeine is a stimulant drug. This means it speeds up the brain and nervous system.

The most common things containing caffeine are:

• coffee
• tea
• cocoa
• chocolate
• cola drinks.

Effects of caffeine

Small amounts of caffeine (less than 600 mg per day) are not harmful. See the caffeine chart at the end of this fact sheet to measure how much caffeine you have.

What caffeine does to you depends on:

• how much you have
• your height and weight
• your general health
• your mood
• whether you have caffeine often
• whether you have caffeine on its own, with food or with other drugs.

Immediate effects

Small amounts

When you have a small amount of caffeine (such as a cup of coffee):

• you feel more awake
• your heart beats faster
• you urinate more
• your body temperature rises
• your digestive system produces more acid.

Large amounts

If you have a large amount of caffeine, you might:

• get headaches
• feel restless
• feel nervous
• become delirious (be confused, have hallucinations or be very excited)
• find it difficult to sleep.

Long-term effects

If you have more than 600 mg of caffeine a day for a long time you may:

• find it difficult to sleep
• worry a lot
• be depressed
• have stomach upsets.

For people who already have heart problems or anxiety disorders such as panic attacks or agoraphobia (being afraid of public places or open spaces), large amounts of caffeine may make the problems worse.

Caffeine and sleep

If you have caffeine before you go to bed, it usually:

• makes it harder to get to sleep
• makes you sleep for a shorter time
• shortens the amount of deep sleep you have
• gives you more 'dream sleep' at first, but less overall. Both deep sleep and dream sleep are important for proper rest.

Caffeine and pregnancy

Having caffeine when you are pregnant is safe if you have normal amounts of caffeine. However, very large amounts of caffeine during pregnancy may lead to losing the baby, the baby being born too early or being born dead.

Doctors recommend that pregnant women have no more than two to four cups of coffee or tea (about 200 mg of caffeine) a day.

Tolerence and dependence

Anyone can develop a 'tolerance' to caffeine. Tolerance means that you must have more of the drug to feel the same effects you used to have with lower amounts.

'Dependence' on caffeine means that it takes up a lot of your thoughts, emotions and activities.

Not all people who take caffeine are dependent.

Withdrawal

People who are dependent on caffeine may experience withdrawal symptoms if they try to stop or cut down the amount of caffeine they have.

Withdrawal symptoms can include:

• headaches
• feeling angry or upset
• tiredness. 

Source: NSW Department of Health