Codeine works by stopping pain signals from travelling along the nerves to the brain.
The most common side effects of codeine are constipation, feeling sick (nausea) and feeling sleepy.
It’s possible to become addicted to codeine, but this is rare if you’re taking it to relieve pain and your doctor is reviewing your treatment regularly.
It may be best not to drink alcohol while taking codeine as you’re more likely to get side effects like feeling sleepy.
Do not give codeine to children under 12 years old. Only give codeine to children aged 12 to 18 years if everyday painkillers like paracetamol and ibuprofen haven’t worked.