Side effects of medicines Ngā pānga kē atu o ngā rongoā

Medicines are used to treat health problems. As well as the effects we want, medicines can cause unwanted effects, known as side effects. All medicines can cause side effects but not everyone gets them. Most are mild and can go away as your body gets used to the medicine. Some side effects can be more serious, such as allergic reactions.

On this page

When to seek immediate medical advice

Call 111 and ask for an ambulance if you or someone you know has:  

  • tongue swelling
  • swelling or tightness in the throat
  • difficulty breathing.  

This could be a severe allergic reaction (anaphylaxis).

Anaphylaxis (severe allergy)

Causes of side effects

 All medicines can cause side effects but not everyone gets them — people respond differently to medicines. Side effects can sometimes be caused or made worse by:

  • taking the medicine with other medicines or supplements
  • taking the medicine with certain foods or alcohol.

If you think a medicine is making you unwell, it is important to talk to your healthcare provider about what to do.

How often side effects happen

The chance of getting side effects is different for each medicine and each person. Some side effects can happen often and others are rare. You might not get any side effects at all.

There are different ways to describe how likely a side effect is with a medicine.

  • Very common — affects more than 1 in 10 people
  • Common — affects between 1 in 10 and 1 in 100 people
  • Uncommon — affects between 1 in 100 and 1 in 1000 people
  • Rare — affects between 1 in 1,000 and 1 in 10,000 people
  • Very rare — affects fewer than 1 in 10,000 people
  • Not known — we do not know how many people are affected.

Lowering your risk of side effects

Before starting a new medicine, talk to your healthcare provider about:

  • anything else you are taking — over-the-counter medicines and supplements can also cause side effects and may react with prescribed medicines
  • if you should avoid any supplements, foods or alcohol while taking your medicine
  • any other medicines that do not suit you — keep a list or apply for a medical alert bracelet or pendant (search online for 'medical bracelets NZ' to find medical bracelet suppliers)
  • any signs to watch out for or precautions to take.

Make sure you are using the medicine exactly as described on the label and on any information you have been given.

How to take medicines

Be aware of an increased risk of falls

Some medicines increase the risk of falls which can be a problem, particularly for older people. Be careful with any medicines that can affect your sense of balance, coordination or awareness. Tell your healthcare provider or pharmacist if you:

  • have any dizziness
  • have any drowsiness
  • feel unsteady on your feet
  • feel sick
  • have any vision problems.

Reporting side effects

Reporting suspected side effects of medicines helps keep medicines safe for everyone. Tell your healthcare provider about any side effects you have. You can also report side effects to the Centre for Adverse Reactions Monitoring. Anyone can do this

Adverse reactions reporting form — Centre for Adverse Reactions Monitoringexternal link