Like all medicines, hydroxychloroquine can cause side effects, although not everyone gets them.
Side effects are more likely when you first start taking it or when your dose is increased. You'll usually feel better after a week or two.
Common side effects
These common side effects of hydroxychloroquine happen in more than 1 in 100 people. There are things you can do to help cope with them:
Stomach pain
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.
Feeling or being sick (nausea or vomiting)
Stick to simple meals and do not eat rich or spicy food. Take your hydroxychloroquine with food. 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.
Skin rashes and itchy skin
Try not to scratch your skin as this will make it worse. Hold something cool on your skin, like a damp towel. Have cool or warm baths or showers, but do not spend a long time in the bath or shower. Use an unperfumed moisturiser regularly.
You can ask your pharmacist to recommend products to help with itchy skin, such as creams, lotions or antihistamines.
Loss of appetite
Eat when you would usually expect to be hungry. If it helps, eat smaller meals more often than usual. Have nutritious snacks that are high in calories and protein, such as dried fruit and nuts.
Headache
Make sure you rest and drink plenty of fluids. Do not drink too much alcohol. Ask your pharmacist to recommend a painkiller.
Talk to your doctor if headaches last longer than a week or are severe.
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
Some people have a serious side effect from hydroxychloroquine.
Tell your doctor or call 111 straight away if you get:
- any eye problems, including changes in the colour of your eye or problems with your eyesight such as blurred vision, sensitivity to light or changes to the way you see colour
- muscle weakness, cramps, stiffness or spasms, or changes in how your skin feels such as tingling
- frequent infections with a high temperature, sore throat or mouth ulcers
- bruising that happens more easily than usual
- signs of low blood sugar (hypoglycaemia), such as sweating or feeling dizzy, shaky or anxious
- skin reactions such as a large area of scaly skin, pus-filled spots together with a high temperature, or your skin becoming more red than usual and being more sensitive to the sun (this may be less obvious on brown or black skin)
- irrational thoughts, feeling anxious, seeing things that are not real (hallucinations), feeling confused or feeling depressed, including thoughts of self harm even if you have never had similar problems before
Serious allergic reaction
In rare cases, hydroxychloroquine may cause a serious allergic reaction (anaphylaxis).
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
If you take hydroxychloroquine for a long time, your doctor will monitor you to check for any long-term side effects.
For example you may have regular full blood counts (tests to check the types and numbers of cells in your blood) and eye examinations.
Your doctor will occasionally check your muscles and tendons to make sure they are working properly.
Other side effects
These are not all the side effects of hydroxychloroquine. 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.
Visit the Yellow Card website for more information about reporting side effects.