Like all medicines, diclofenac can cause side effects in some people, but many people have no side effects or only minor ones.
Side effects usually improve as your body gets used to the medicine.
Common side effects of diclofenac
These common side effects of diclofenac tablets, capsules and suppositories happen in more than 1 in 100 people. There are things you can do to help cope with them:
Feeling sick or being sick
Stick to simple meals and do not eat rich or spicy food. It might help to take or use your diclofenac after you've eaten.
If you're being sick, try small frequent sips of water to avoid dehydration. Signs of dehydration include peeing less than usual or having dark, strong-smelling pee.
If you take the combined contraceptive pill or the progestogen-only pill and you're being sick, your contraception may not protect you from pregnancy. Check the pill packet for advice.
Diarrhoea
Drink lots of fluids, such as water or squash, to avoid dehydration. Speak to a pharmacist if you have signs of dehydration such as peeing less than usual or having dark, strong-smelling pee. Do not take any other medicines to treat diarrhoea without speaking to a pharmacist or doctor.
If you take the combined contraceptive pill or the progestogen-only pill and you have severe diarrhoea for more than 24 hours, your contraception may not protect you from pregnancy. Check the pill packet for advice.
Feeling dizzy or vertigo
If you feel dizzy or unsteady, stop what you're doing and sit or lie down until you feel better. Do not drive or cycle, or use tools or machinery if you're feeling dizzy or lightheaded.
As your body gets used to diclofenac, these side effects should wear off.
Headaches
Make sure you rest and drink plenty of fluids. Do not drink too much alcohol. Ask your pharmacist to recommend an alternative painkiller.
Talk to your doctor if headaches do not go away or are severe.
Stomach ache
Try to rest and relax. It can help to eat and drink slowly and have smaller and more frequent meals. Putting a heat pad or covered hot water bottle on your stomach may also help.
If you are in a lot of pain, speak to your pharmacist or doctor.
Wind (farting)
Try not to eat foods that cause wind (like lentils, peas, beans and onions). Eat smaller meals, eat and drink slowly, and exercise regularly.
There are pharmacy medicines that can also help, such as charcoal tablets or simeticone.
Loss of appetite
Eat when you would usually expect to be hungry. If it helps, eat smaller meals more often than usual. Snack when you're hungry. Have nutritious snacks that are high in calories and protein, such as dried fruit and nuts.
Mild rash
Use an emollient cream or ointment to moisturise, soothe and hydrate the affected area. If it does not get better within a week or you're worried, speak to a pharmacist or doctor.
You're less likely to have side effects with diclofenac gel or plasters. This is because less medicine gets into your body. But you may still get side effects, especially if you use a lot on a large area of skin.
There are things you can do to help cope with them:
More sensitive to sunlight than normal
Stay out of bright sun and use a high factor sun cream (SPF 30 or above), even on cloudy days. Do not use a sunlamp or sunbeds.
Itching or mild rash where you applied the gel or plaster
It may help to take an antihistamine – you can buy this from a pharmacy. Check with the pharmacist to see what type is suitable for you.
Dry or irritated skin
Apply a moisturiser. Often the best type of moisturiser is an oil-free moisturiser for sensitive skin.
Try to keep your showers shorter than 2 minutes, using lukewarm water rather than hot.
If your skin is irritated, try using the gel less often (maybe once a day instead of twice, or every other day), or you could stop using the gel for a few days until the irritation goes away and then try using it again.
If the irritation does not go away, stop using the gel and speak to your doctor.
Speak to a doctor or pharmacist if the advice on how to cope does not help and a side effect is still bothering you or does not go away.
Serious side effects
These serious side effects are rare and happen in less than 1 in 1,000 people.
Call your doctor or call 111 straight away if:
- you have black poo – this could be a sign of bleeding in your stomach or gut
- you have severe indigestion, heartburn or stomach pain, vomiting or diarrhoea – these can be signs of an ulcer or inflammation in your stomach or gut
- the whites of your eyes or your skin turn yellow, although this may be less obvious on brown or black skin – this can be a sign of liver problems
- you have a raised, itchy rash, or swollen or puffy skin – these can be signs of hives (urticaria) or oedema (swelling)
- you have breathlessness, tiredness and swollen legs or ankles – these can be signs of heart failure
Immediate action required: Call 999 or go to A&E if:
- you have blood in your vomit – this could be a sign of bleeding in your stomach or gut
Immediate action required: Call 999 if:
- you have chest pain, shortness of breath, feel weak or lightheaded, or have an overwhelming feeling of anxiety – these can be signs of a heart attack
- you have weakness on one side of your body, trouble speaking or thinking, loss of balance or blurred eyesight – these can be signs of a stroke
Do not drive yourself to A&E.
The person you speak to at 999 will give you advice about what to do.
Serious allergic reaction
It's possible to have a serious allergic reaction (anaphylaxis) to diclofenac.
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.
Do not drive yourself to A&E.
The person you speak to at 999 will give you advice about what to do.
Long-term side effects
Diclofenac tablets and capsules can cause an ulcer in your stomach if you take them for a long time or in large doses, or if you're older or in poor general health.
If you have a stomach ulcer or have ever had one, you may not be able to take diclofenac tablets or capsules. Your doctor will prescribe another medicine.
There's also a small risk of heart failure or kidney failure if you take the maximum dose (150mg a day) for a long time.
It's best to take the lowest dose that works for the shortest possible time.
Other side effects
These are not all the side effects of diclofenac. For a full list, see the leaflet inside your medicine packet.
Reporting side effects
You can report any suspected side effect using the Yellow Card safety scheme.