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10-minute read

Key facts

  • Caffeine is a stimulant that acts on your brain and nervous system.
  • Caffeine is found naturally in coffee, tea leaves, cocoa beans, guarana and chocolate.
  • Caffeine is addictive and you may develop withdrawal symptoms when reducing your intake.

What is caffeine?

Caffeine is a chemical found in foods and drinks. It can stimulate your brain and nervous system.

It is found in:

  • coffee
  • tea leaves
  • cocoa beans
  • guarana — a South American plant with high levels of natural caffeine
  • chocolate
  • cola drinks
  • energy drinks

Caffeine and medicines

Caffeine can also be found in some prescription and over-the-counter medicines, such as some:

How will caffeine affect my body?

Caffeine affects everyone differently.

The effect of caffeine depends on:

  • your height, weight and general health
  • the amount you eat or drink
  • genetic factors
  • whether you regularly eat or drink caffeine
  • whether other food or drugs (including alcohol) are taken at the same time
  • your mood

Caffeine stays active for longer in the bodies of:

  • babies
  • pregnant women
  • older people

People with existing medical conditions, such as high blood pressure, may be more sensitive to caffeine. This can make a normal amount of caffeine more dangerous. If you have an existing medical condition, it’s a good idea to eat or drink less caffeine.

It’s not always clear how your body will respond to caffeine. Much of the medical research in this area has been into coffee, which contains caffeine and many other ingredients.

How much caffeine does it contain?

The amount of caffeine in food and drinks varies. For example, an espresso has more caffeine than instant coffee. Similarly, dark chocolate has more caffeine than milk chocolate.

Source Caffeine (mg)
Espresso (50mL cup) 145
Energy drink (250mL can) 80
Instant coffee (1 teaspoon) 80
Black tea (250mL cup) 50
Cola (375mL can) 36
Milk chocolate (50g bar) 10

How much caffeine is safe?

It is recommended that healthy adults can safely consume around 400mg of caffeine a day. This is the same as:

  • 2 espressos
  • or 4 instant coffees
  • or 8 cups of tea

Children under 18 years should consume less than 3mg for each kilo of body weight a day. For a 40kg child, this is about 120mg a day, or 2 cans of cola (375mL). There is evidence that amounts greater than this can cause increased anxiety.

If you are pregnant or breastfeeding, it’s a good idea to limit your intake of caffeine to 200mg per day. That is 1 espresso, or 2 instant coffees or 4 cups of tea.

People who are pregnant or breastfeeding should limit their caffeine intake. caffeine stays active in your body for longer in pregnant women and babies.

About 1% of the caffeine you eat or drinks gets into your breastmilk. The caffeine level in your breastmilk usually peaks about one hour after eating or drinking it.

People with health conditions should talk to their doctor about caffeine as part of any discussion about a healthy lifestyle.

What are the health benefits of consuming caffeine?

The effect of caffeine on your health is complex. It can cause some health problems, but it can also reduce your chances of having others. Because caffeine is a stimulant, it can make you feel more alert and energetic.

There is some evidence that people who drink a moderate amount of caffeine regularly might have a lower risk of:

Most of these studies have looked at caffeine from coffee only.

What are the short-term effects of consuming caffeine?

The short-term effects of caffeine typically happen about 30 minutes after consumption. They can last up to 6 hours, depending on the individual.

Short-term effects after a small amount of caffeine (100-200mg) can include:

  • feeling more alert and active
  • higher body temperature
  • faster breathing and heart rate
  • increased production of stomach acid

Children and young people who consume energy drinks containing caffeine may also have:

What are the long-term problems with consuming caffeine?

We do know that many regular coffee drinkers become dependent on caffeine. Regular heavy use of caffeine, more than 600mg a day, can cause:

There is also evidence to show that caffeine consumption during pregnancy can increase the risk of:

Much of the research into the effects of caffeine has only looked at coffee. We still don’t know much about other caffeine containing foods and drinks.

Mixing caffeine with alcohol and other drugs

Drinking or eating caffeine when taking other drugs can be unpredictable and increase your risk of harm.

Caffeine and medicines

Caffeine can interact with over-the-counter and prescription medicines, such as:

Ask your pharmacist or doctor if any medicines that you take could be affected by caffeine.

Caffeine, alcohol and illicit drugs

When you drink alcohol with caffeine, the caffeine can hide some of the effects of the alcohol. This can cause you to drink more and lead to more risk-taking behaviours.

Caffeine does not affect the way your body absorbs alcohol. It will not reduce your blood alcohol concentration or help you 'sober up' after a big night.

Caffeine can also interact with other stimulants such as cocaine and methamphetamine. It can increase your risk of problems such as an abnormal health rate or heart rhythm.

How can I reduce my caffeine intake?

If you want to reduce or stop consuming caffeine, it’s a good idea to do this gradually. For example, drink one less caffeinated drink each day.

Other options are:

  • coffee drinkers can gradually switch to decaffeinated coffee
  • tea drinkers can reduce the brew time or switch to herbal teas

Remember, if you are reducing your caffeine intake always check food and drink labels for caffeine.

Caffeine withdrawal syndrome

Because caffeine is a drug, if you stop consuming caffeine you may develop withdrawal syndrome. Symptoms usually start a day or two after stopping caffeine. These symptoms can last up to a week, and include:

Resources and support

You can find out more about caffeine through the Alcohol and Drug Foundation — call their Drug Info and Advice Line on 1300 85 85 84.

You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with 24 hours a day, 7 days a week.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: August 2023

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