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 they mean 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 increasing that dose gradually over time, 
  • taking the medicine with meals (e.g. anti-inflammatory medicines), 
  • taking the medicine on an empty stomach (eg, some antibiotics) 
  • taking the medicine at a particular time of the day, or even 
  • staying out of the sun (eg, 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 side effects are common and others 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 a consumer medicine information (CMI) leaflet 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 are having trouble managing, 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 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.

Be aware that if you are considering a newly approved medicine, it is possible that side effects that are less common or only show up with ling term use may not have been reported yet.

Beware of unreliable information

Although you might be interested to hear about other people’s experiences with a medicine, remember that not everyone who takes the same medicine will have side effects, or have the same side effects. This is particularly important if you are searching online for experiences with medicines. Remember that many online discussions about medicines and side effects are unreliable. The best person to talk to is your health professional.

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 are having trouble managing, 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

If you experience side effects that require a change of medicine or a reduction in dose, it is important for your health professional to update your health record with this information.

A health professional may report to the TGA any new or unusual medicine-related side effects they observe or that are reported to them by their patients . Reports to the TGA are confidential. 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.

What are 'adverse events'?

Adverse events are unintended and sometimes harmful occurrences associated with the use of a medicine, vaccine or medical device.

They include side effects to medicines and vaccines, and problems or incidents involving medical devices.

Importantly, an adverse event is not always caused by the therapeutic good itself. An adverse event could be a result of incorrect user interaction or other circumstances such as two properly functioning devices that do not operate as intended when used in combination. The occurrence of an adverse event does not necessarily mean that there is something wrong with the therapeutic good.

Therapeutic Goods Administration. Reporting adverse events. Australian Government Department of Health, 2021 (accessed 21 April 2021).

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). 

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.