Healthdirect Free Australian health advice you can count on.

Medical problem? Call 1800 022 222. If you need urgent medical help, call triple zero immediately

healthdirect Australia is a free service where you can talk to a nurse or doctor who can help you know what to do.

beginning of content


6-minute read

What is caffeine?

Caffeine is a stimulant that acts on the brain and nervous system. It is found in coffee, most teas, cocoa, chocolate, cola, guarana and energy drinks. Caffeine's effect on your health is complex — it can cause minor health problems, but it can also reduce your chances of having others.

Pregnant or breastfeeding women and children should restrict their caffeine intake.

How do we consume caffeine?

Most adults get most of their caffeine from coffee. Other common sources are tea, chocolate bars, chocolate drinks, cola drinks and energy drinks. The amount of caffeine in each of these varies, even within 1 source. For example, espresso has more caffeine than instant coffee, and dark chocolate has more caffeine than milk chocolate.

The research is not clear, but it is likely that healthy adults can in general consume around 400mg of caffeine a day safely.

Source Caffeine (mg)
Espresso (50mL cup) 145
Energy drink (250mL can) 80
Instant coffee (1 teaspoon) 80
Dark chocolate (50g bar) 60
Black tea (250mL cup) 50
Cola (375mL can) 36
Milk chocolate (50g bar) 10


Caffeine is also found in some medications that relieve pain and treat colds and flu. Some energy supplements, appetite suppressants and weight loss products may contain caffeine too.

How does caffeine affect the body?

Caffeine affects many parts of your body, including the central nervous system, muscles, heart, lungs and kidneys.

However, it is hard to say exactly how the body responds to it. Much of the medical research in this area has been into coffee, which contains caffeine but also many other ingredients.

We do know that caffeine is addictive, and many regular coffee drinkers become dependent on it.

What are the benefits of consuming caffeine?

Because caffeine is a stimulant, it can make you feel more alert and energetic.

Also, people who drink coffee regularly might have a lower than average risk of:

  • type 2 diabetes — possibly because caffeine makes you more sensitive to the insulin your body produces
  • depression — possibly because some of the naturally occurring chemicals in caffeine can reduce inflammation of sensitive parts of the brain
  • Parkinson's disease — possibly because it protects the brain cells at risk of damage in someone who has Parkinson's disease
  • bowel cancer — possibly because it contains the naturally occurring chemicals cafestol and kahweol, which both protect against cancer
  • Alzheimer's disease — in this case, it is not clear why caffeine might be beneficial

And overall, it seems that coffee drinkers live longer than people who do not drink coffee. It is not clear if that is due to the coffee or to something else.

What are the problems with consuming caffeine?

Too much caffeine at any one time — for example, more than 500mg, which is 3 espresso coffees or 6 to 7 instant coffees — can make you feel agitated and anxious. It can make it hard for you to sleep. It may also make you breathe faster and your heart beat faster.

If you drink a lot of coffee over a long period, it might increase your risk of:

  • heartburn — possibly because coffee relaxes the muscle that stops acid regurgitating into the oesophagus
  • osteoporosis — probably because caffeine encourages you to lose calcium through your kidneys
  • insomnia — because of the stimulant effect
  • miscarriage — in this case, it is not clear why there might be an increased risk
  • infertility in men — possibly because caffeine damages sperm

What are the areas of uncertainty?

It used to be thought that caffeine caused high blood pressure and dehydration, but now it seems this might not be true.

Coffee has been said to reduce a woman's fertility, but that also is probably not true.

Mixing caffeine with alcohol and other drugs

When alcohol is consumed with or mixed with caffeine — as it is in certain energy drinks — the caffeine can hide some of the effects of the alcohol. This can make drinkers feel more alert. As a result, they may drink more alcohol and become more impaired than they realise, putting themselves at greater risk.

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

Caffeine can also interact with other drugs such as:

Talk to your pharmacist or doctor to check if any medications you take could be affected by caffeine.

How much caffeine is it safe to consume?

The research is not clear, but it is likely that healthy adults can generally consume around 400mg of caffeine a day — that is 2 (50mL) espresso coffees or 5 (250mL) energy drinks.

Children should consume less than 3mg for each kilo of body weight a day. For children aged 9 to 13, this is about 120mg a day, or 2 (375mL) cans of cola. If you are pregnant or breastfeeding it is a good idea to limit your intake to 200mg per day — that is 1 espresso, 2 instant coffees or 4 cups of tea. See the table above for details on serving sizes.

But some people are particularly sensitive to caffeine — if you find that 1 coffee per day gives you a racing heart, then give it up.

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

Withdrawing from caffeine

Because caffeine is addictive, many people have withdrawal symptoms after a day or two without it. These symptoms can last for a few days, and include:

If you want to reduce the amount of caffeine you consume, it is a good idea to do this gradually. For example, reduce your intake over a couple of weeks and avoid cutting down by more than 1 caffeinated drink between consecutive days. Another option for coffee drinkers is to gradually switch to decaffeinated coffee.

Check labels on foods and drinks. But keep in mind that only added caffeine is labelled — if caffeine is found naturally, such as in guarana, it will not be listed.

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

Last reviewed: April 2021

Back To Top

Need more information?

These trusted information partners have more on this topic.

Top results

Caffeine during pregnancy

Some foods, drinks and medication contains caffeine and you should limit the amount of caffeine you consume during pregnancy and while you are breastfeeding.

Read more on Pregnancy, Birth & Baby website

Caffeine - Better Health Channel

Caffeine is a stimulant that acts on the brain and nervous system.

Read more on Better Health Channel website

Caffeine in pregnancy | Parenthub

Pregnancy Pregnancy and Food Caffeine in pregnancy ( 5 votes, average: 4

Read more on Parenthub website

Caffeine and breastfeeding | Australian Breastfeeding Association

Like drinking coffee but wonder if it's okay for your baby?

Read more on Australian Breastfeeding Association website

Caffeine | Your Fertility

Are you trying to conceive and wondering if caffeine is affecting your Fertility? Visit the health and medical section of our website for more information.

Read more on Your Fertility website

Caffeine and Energy Drinks Effects and Withdrawal Symptoms | Your Room

Caffeine and energy drinks, when consumed in large quantities, can cause unwanted side effects. Find out about withdrawal symptoms and other FAQs.

Read more on NSW Health website

Eyes wide shut: how caffeine can affect your sleep | Jean Hailes

It's often the first ritual in our day, but just how much caffeine is in that morning cup of coffee or tea

Read more on Jean Hailes for Women's Health website


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.

Read more on NSW Health website

Caffeine - Alcohol and Drug Foundation

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.

Read more on Alcohol and Drug Foundation website

Effects of caffeine, alcohol and smoking on reproductive outcomes

Some lifestyle behaviours are known to affect fertility, pregnancy health and the health of the baby at birth and in adulthood. Here is what you need to know about how caffeine, alcohol and smoking affect fertility and reproductive outcomes.

Read more on Your Fertility website

Healthdirect 24hr 7 days a week hotline

24 hour health advice you can count on

1800 022 222

Government Accredited with over 140 information partners

We are a government-funded service, providing quality, approved health information and advice

Australian Government, health department logo ACT Government logo New South Wales government, health department logo Northen Territory Government logo Government of South Australia, health department logo Tasmanian government logo Victorian government logo Government of Western Australia, health department logo

Healthdirect Australia acknowledges the Traditional Owners of Country throughout Australia and their continuing connection to land, sea and community. We pay our respects to the Traditional Owners and to Elders both past and present.