Understanding side effects

When you are trying to decide if a medicine is right for you, you might want to know its potential side effects. Here are some pointers to understanding the side effects of your medicine.

What are the medicine's side effects?

Side effects, also called adverse reactions, are the unintended effects of a medicine.

Side effects are one kind of ‘risk’ or unwanted effect. Others are:

  • interactions with other medicines or food
  • the medicine not having the desired effect.

Sometimes medicines have good side effects. For example, the diabetes medicine metformin (e.g. Glucophage) has the good side effect of weight loss.

If you have concerns about side effects, talk to your health professional.

Video transcript

On their website, it would’ve been great for them to list ‘Yes, there are these serious side effects — however, this is the incidence of them occurring’.

Okay, so, a doctor suggested that my daughter who was suffering from asthma — or we thought it was asthma — look at some. He suggested a drug for her to take, so I went and got the prescription for the drug and then looked at the consumer information. One of the first things it mentioned was all medications have risks when you take them, so I thought yes, I will read the side effects and when I read them it was things like — and my daughter is 6 years old — severe anxiety, aggression, sleepwalking, nightmares, depression, anxiety, suicidal thoughts, and for something that was essentially a cough, I thought that it was a little bit extreme.

So that was just looking up online on their websites, so then I tried to find some more information and, basically, it was just different companies or organisations rehashing the same sorts of information, there wasn’t really any breakdown.

So then I rang my friend who has a lot of experience with medical research, and she found some reports on particular tests on that drug and, yes, there were side effects, but they weren’t in children, and they had been a very large sample of people that had been tested, and it was a very, very small incidence of those things occurring — and, as I said, not in children. So then it put it in perspective. So without the information about how prevalent those side effects might be, it would have completely stopped me from using that medication for my daughter.


Questions to ask about side effects

All medicines have possible side effects, but not everybody will experience them.

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?

You then need to weigh up the risk of side effects against the benefits of the medicine — see What will the medicine do for me? and Is this medicine right for me?

Sometimes it is helpful to take notes when you are talking to your health professional. You’ll get more out of a visit to your doctor, pharmacist or other health professional if you ask the right questions about your medicines or medical tests.

If you are trying to decide between treatments, filling in the Personal decision guide for medicines may help you compare your different options.

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, 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 experience of 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.

How common are the medicine’s side effects?

It can be daunting to see all the potential side effects listed for a medicine. But 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).

How often do common side effects occur?

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

Click on a rate of risk button below (e.g. 'Very common', 'Rare' etc) to get an idea of how likely each one is.

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 get a certain side effect.

Are there any serious side effects?

For most medicines, the serious side effects are less common. However, even side effects that might not be considered ‘serious’ (such as nausea) might affect your ability to tolerate the medicine.

For a small number of medicines, the serious side effects are also the most common. These are prescribed only in certain situations when the benefits are likely to outweigh the potential harms.

Some chemotherapy medicines for cancer treatment have a common side effect of reducing your number of white blood cells. This would increase your risk of infection, but the benefit to you in terms of treating the cancer might far outweigh the harm of this side effect. If you were treating a less serious illness, like hayfever, the benefit wouldn’t be worth the risk of reducing your number of white blood cells.

If your medicine has a serious side effect that worries you, ask your health professional how often it happens and whether you can do anything to avoid it.

Can I do anything to avoid or reduce the 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.

Can I do anything to avoid interactions?

Some unwanted effects can occur because of interactions with foods, alcohol or other medicines, including vitamins, herbal or complementary medicines. Asking your health professional about the possibility of interactions with your medicine will help you avoid these. See Understanding interactions

Keeping a Medicines list will make it easier for your health professional to spot potential interactions.

Will the side effect get better with time?

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 should I do if I am worried about a side effect?

Always discuss any side effects with your health professional. If there are any 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. See What will the medicine do for me?

Adverse Medicine Events line

The Adverse Medicine Events (AME) Line lets you report and discuss side effects that might be related to your medicine. The side effects of your medicine — but not your personal details — are reported to the Australian medicines regulatory agency — the Therapeutic Goods Administration (TGA). This information helps to improve the safe use of medicines. You can call the AME Line on 1300 134 237 (Mon–Fri, 9am–5pm EST).

The AME line is not for emergencies. 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.

Video transcript

It’s important to know what your medications are doing. First of all, if you understand and you get some side effects and they are the side effects that go with the medication; for instance, an example would be constipation — which is very common in the elderly — then you probably would be able to deal with it yourself, by either going to the chemist or what you would normally do for your bowels.

That’s just one example, but if you’re feeling nauseated, it’s not a very nice feeling. If it persists, then you need to go to your doctor to find out if you continue with it, or if you need to go onto something else which may do the same thing but not have that side effect.