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Side effects of codeine

Like all medicines, codeine can cause side effects in some people. But many people have no side effects or only minor ones.

The higher the dose of codeine the more chance that you will get side effects.

Common side effects

These common side effects of codeine happen in more than 1 in 100 people. There are things you can do to help cope with them:

Constipation

Try to get more fibre into your diet, such as fresh fruit, vegetables and cereals. Try to drink several glasses of water or other non-alcoholic liquid each day. If you can, it may also help to do some gentle exercise.

It's safe to use a laxative if your constipation does not go away. Usually, lactulose is best but check with a pharmacist or doctor first.

Feeling or being sick (nausea or vomiting)

Take codeine with or just after a meal or snack to ease feelings of sickness. If you're being sick, try small frequent sips of water. This side effect should normally wear off after a few days. Talk to your doctor about taking an anti-sickness medicine if it carries on for longer.

If you take the combined contraceptive pill or progestogen-only pill and you're being sick, your contraception may not protect you from pregnancy. Check the pill packet to find out what to do.

Feeling sleepy

This side effect should go away within a few days as your body gets used to codeine. Talk to your doctor if it carries on for longer. Do not drive, cycle or use tools or machinery if you're feeling sleepy.

Confusion (unable to concentrate or think clearly, muddled thoughts)

This side effect should wear off within a few days as your body gets used to codeine. Talk to your doctor if it carries on for longer.

Do not drive, cycle or use tools or machinery. GOV.UK has more information on the law on drugs and driving.

Feeling dizzy and vertigo

If codeine makes you feel dizzy when you stand up, try getting up very slowly or stay sitting down until you feel better. If you begin to feel dizzy, lie down so that you do not faint, then sit until you feel better.

Do not drive, cycle or use tools or machinery if you're feeling dizzy. GOV.UK has more information on the law on drugs and driving.

Dry mouth

Try chewing sugar-free gum or sucking sugar-free sweets. Your doctor can also prescribe an artificial saliva substitute to keep your mouth moist. This comes as a spray, gel or lozenge.

Headaches

It's safe to take an everyday painkiller such as paracetamol or ibuprofen. Talk to your doctor if the headaches get worse or last longer than a week.

If this advice does not help and any of these side effects continue to bother you, speak to your doctor or pharmacist.

Serious side effects

Serious side effects happen in less than 1 in 100 people.

Call a doctor or call 111 now if you:

  • have muscle stiffness
  • get symptoms of low blood pressure, which include feeling dizzy and tired

Immediate action required: Call 999 or go to A&E now if:

  • you have breathing difficulty or short, shallow breathing
  • you have a fit or seizure

Find your nearest A&E

Serious allergic reaction

In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to codeine.

Immediate action required: Call 999 now if:

  • your lips, mouth, throat or tongue suddenly become swollen
  • you're breathing very fast or struggling to breathe (you may become very wheezy or feel like you're choking or gasping for air)
  • your throat feels tight or you're struggling to swallow
  • your skin, tongue or lips turn blue, grey or pale (if you have black or brown skin, this may be easier to see on the palms of your hands or soles of your feet)
  • you suddenly become very confused, drowsy or dizzy
  • someone faints and cannot be woken up
  • a child is limp, floppy or not responding like they normally do (their head may fall to the side, backwards or forwards, or they may find it difficult to lift their head or focus on your face)

You or the person who's unwell may also have a rash that's swollen, raised, itchy, blistered or peeling.

These can be signs of a serious allergic reaction and may need immediate treatment in hospital.

Long-term side effects

Some people with conditions that need long-term pain relief may need to take codeine for a long time.

If you need to take it for a long time your body can become used to it (known as tolerance). That means you need higher doses to control your pain over time.

Some people can become more sensitive to pain (hyperalgesia). If this happens, your doctor will reduce your dose gradually to help these symptoms.

It's possible to become addicted to codeine. For this reason, your dose will be reviewed to make sure you're only having the amount you need to control your pain.

Your treatment plan may include details of how and when you'll stop codeine.

If you're having treatment for cancer pain or other severe pain, your pain control will be carefully monitored. Speak to your doctor if you're worried about tolerance, hyperalgesia or becoming addicted.

Other side effects

These are not all the side effects of codeine. For a full list, see the leaflet inside your medicine packet.

Information:

You can report any suspected side effect using the Yellow Card safety scheme.

Visit Yellow Card for further information.

Page last reviewed: 31 January 2022
Next review due: 31 January 2025