Like all medicines, morphine can cause side effects in some people, but many people have no side effects or only minor ones.
The higher the dose of morphine you take, the more chance that you will get side effects.
Common side effects
These common side effects of morphine 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 and vegetables and cereals. Try to drink several glasses of water each day. If you can, it may also help to do some gentle exercise.
It's likely you will need to take a laxative to help prevent or treat constipation caused by morphine. Ask your doctor if you are not taking a laxative or if your constipation symptoms do not go away.
Feeling or being sick (nausea or vomiting)
Take morphine with or just after a meal or snack to help feelings of sickness. This side effect should normally wear off after a few days. Talk to your doctor about taking anti-sickness medicine if it carries on for longer.
If you're being sick, take small, frequent sips of water or other fluids to avoid dehydration. Signs of dehydration include peeing less than usual or having dark, strong smelling pee.
If you take contraceptive pills and you're being sick (vomit), your contraception may not protect you from pregnancy. Check the pill packet for advice.
Feeling sleepy or tired
These side effects should wear off within a week or two as your body gets used to morphine. Talk to your doctor if they carry on for longer.
Feeling dizzy or a sensation of spinning (vertigo)
Stop what you're doing and sit or lie down until you feel better. Do not drink alcohol as it will make these side effects worse. If the feeling does not go away, do not take any more medicine and speak to a pharmacist or your doctor.
Do not drive, ride a bike or use tools or machinery. GOV.UK has more information on the law on drugs and driving.
Confusion
Talk to your doctor if you feel confused, as your dose may need to be adjusted.
Headaches
Make sure you rest and drink plenty of fluids. It may be best not to drink alcohol while taking morphine as this can make headaches worse. Ask your pharmacist to recommend a painkiller.
Headaches should usually go away after the first week of taking morphine. Talk to your doctor if they last longer than a week or are severe.
Itchy skin or a rash
It may help to take an antihistamine which you can buy from a pharmacy. Check with the pharmacist to see what type is suitable for you.
If symptoms do not go away or get worse talk to your doctor as you may need to try a different painkiller.
Talk to your doctor or pharmacist if the advice on how to cope does not help and these side effects bother you or do not go away.
Do not take any other medicines to treat the side effects of morphine without speaking to your pharmacist or doctor.
Serious side effects
Serious side effects happen in less than 1 in 100 people.
Call your doctor or call 111 now if you:
- have muscle stiffness
- feel dizzy, tired and have low energy – this could be a sign of low blood pressure
Immediate action required: Call 999 or go to A&E if you or your child:
- have a seizure or fit
- have difficulty breathing or short shallow breathing
Serious allergic reaction
In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to morphine.
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 morphine 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 morphine. 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 morphine.
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 morphine. For a full list see the leaflet inside your medicines packet.
You can report any suspected side effect using the Yellow Card safety scheme.