Medicine and side effects

Side effects, also called adverse reactions, are the unintended effects of a medicine. All medicines have possible side effects, but not everybody will experience them. When you are recommended a medicine, it's important to ask questions about side effects and what this means for you.


How can I avoid or reduce side effects?

Some side effects can be avoided by following the specific instructions for that medicine. 

For some medicines, these instructions could include starting with a low dose and building up, taking the medicine with meals (e.g. anti-inflammatory medicines), taking it on an empty stomach (e.g. antibiotics) or taking it at a particular time of the day, or even staying out of the sun (e.g. the antibiotic doxycycline).

If you are having trouble with side effects of a medicine, talk to your health professional about it. There may be other ways to take the medicine or even other medicines that might suit you better.

Knowing whether side effects can be managed may help you when deciding whether to start new medicines.

Some side effects get better with time. Nausea is typical of this — some medicines make you nauseous for the first few days or even weeks, but the nausea then goes away.

Other side effects do not go away, or do not occur straight away. Knowing if a side effect is long term or short term can affect your decision about whether to take a particular medicine.

What does common side effect mean?

Not all side effects are as likely as others, and some people will not experience any side effects at all. Some are common and some are rare. Some are also more serious than others.

The terms ‘common’, ‘uncommon’ and ‘rare’ have a very specific meaning when used to describe side effects for medicines in official documents such as consumer medicine information (CMI) or the product information (PI).

Term Estimated number of people affected Estimated % of people affected
Very common At least 1 in 10 people At least 10% of people
Common Between 1 and 10 in every 100 people Between 1% and 10% of people
Uncommon Between 1 and 10 in every 1000 people Between 0.1% and 1% of people
Rare Between 1 and 10 in every 10,000 people Between 0.01% and 0.1% of people
Very rare Fewer than 1 in 10,000 people Fewer than 0.01% of people

If you don’t understand how likely a side effect is, ask your health professional to explain using words or numbers that make sense to you.

Although this sort of information can give you an idea of how often side effects occur on average, it does not tell you how likely you are to experience a particular side effect. Your individual risk of a side effect depends on several factors including your other health issues, your age and the dose of medicine. Your health professional may be able to tell you how likely they think you are to experience a certain side effect.

Questions to ask about side effects

When finding out about side effects, important questions to ask your health professional are:

  • What are the possible side effects?
  • How common are the side effects?
  • Are there any serious side effects and how likely are these?
  • Can I do anything to avoid or reduce the side effects?
  • Will the side effect get better with time?
  • What should I do if I am worried about a side effect?

Always discuss any side effects with your health professional. If there are side effects you can’t cope with, there may be things your health professional can do to combat them, such as reduce the dose of your medicine or switch to another treatment.

When you are finding out about side effects, remember to weigh these up against the benefits of the medicine when you make any choices about treatment. 

Where can I get information about side effects?

One source of information about possible side effects is the consumer medicine information (CMI) that must be produced for all prescription (and some non-prescription) medicines.

The CMI describes common and important side effects that are known about from clinical trials and ongoing monitoring of medicines by health professionals. You may find it helpful to read the CMI and then discuss any particular concerns or questions with your health professional before you buy the medicine.

You can download a CMI from our Medicine Finder or you can ask your health professional for the CMI for your medicine.

Although you might be interested to hear about other people’s experiences with a medicine, remember that not everyone will have the same, or any, side effects.

Be aware that if you are considering a newly approved medicine it is possible that longer-term or less common side effects may not have been discovered yet.

Read more in Finding good information about medicines.

What can I do if I experience a side effect?

Always discuss any side effects with your health professional. If there are side effects that you can’t cope with, there may be things your health professional can do to combat them, such as reduce the dose of your medicine, or switch to another treatment.

  • If you have concerns about your medicines arising from an overdose or suspected poisoning, call the Poisons Information Centre, 24 hours a day on 13 11 26. 
  • For general emergencies call 000.
  • If the side effect is not an emergency, there are a number of ways you can report it to the Therapeutic Goods Administration (TGA). 

Advise your health professional

Your health professional may report new or unusual medicine-related side effects they observe or that are reported to them by their patients to the TGA. Your personal information will remain confidential and your privacy will be maintained.

Call the Adverse Medicines Events (AME) Line on 1300 134 237

The AME Line is a service that encourages members of the public to report and discuss side effects that might be related to their medicine. Medicine-related side effects are reported to the TGA for assessment and contribute to national medicine safety efforts. Your personal information will remain confidential and your privacy will be maintained. 

The AME Line is available Monday to Friday, 9 am to 5 pm AEST. It is not for emergencies.

Report side effects directly to the TGA

You can report suspected side effects directly to the TGA via their website.

Each report that the TGA receives is collected in a publicly accessible national database, the Database of Adverse Event Notifications (DAEN). This database includes adverse event reports about prescription medicines, over-the-counter medicines and complementary medicines (vitamins, minerals, herbal or natural medicines). ‘Adverse events’ includes both side effects and other problems that may occur while using a medicine which turn out not to be a medicine-related side effect.

The information is regularly analysed so that any potential safety concerns can be investigated in detail. If the TGA identifies a new safety concern such as a new side effect, it can take action to address it and make sure that health professionals and the public are aware of it.