Like all medicines, doxycycline can cause side effects, although not everyone gets them.
Common side effects
These common side effects of doxycycline happen in around 1 in 10 people. There are things you can do to help cope with them:
Headaches
Make sure you rest and drink plenty of fluids. Painkillers, such as paracetamol and ibuprofen, are safe to take with doxycycline.
Feeling sick (nausea)
Stick to simple meals without rich or spicy food. It might help to take doxycycline after a meal or snack or with a drink of milk instead of water.
Being sick (vomiting)
If you are being sick, take small sips of water or squash, to avoid dehydration. Signs of dehydration include peeing less than usual or having dark, strong-smelling pee.
Do not take any medicines to treat vomiting without speaking to a pharmacist or doctor first.
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 being sensitive to sunlight
When you go outside, wear clothes that cover you up, a hat and sunglasses. Use sunscreen or sunblock on your skin, with a high sun protection factor (SPF) of at least 30 to prevent sunburn. If you have fair skin, you may need a higher number of up to SPF 50.
Use a sunscreen product for your lips. Do not use sunlamps or tanning beds.
Speak to a doctor or pharmacist if the advice on how to cope does not help and the side effect is still bothering you or does not go away.
Serious side effects
Serious side effects are rare and happen in less than 1 in 1,000 people.
Call 111 or call a doctor now if you have:
- bruising or bleeding you cannot explain (including nosebleeds), a sore throat, high temperature and feeling tired or generally unwell – these can be signs of blood problems
- diarrhoea (possibly with stomach cramps) that contains blood or mucus – if you have severe diarrhoea that lasts longer than 4 days, also speak to a doctor
- ringing or buzzing in your ears
- pale poo and dark pee, and the whites of your eyes turn yellow or your skin turns yellow (although this may be less obvious on brown or black skin) – these can be signs of liver problems
- joint or muscle pain since starting doxycycline
- severe headaches, vomiting and problems with your vision – these could be signs of pressure around your brain (intracranial hypertension)
- a fingernail that starts coming away from its base – this could be a reaction to sunlight called photo-onycholysis
- a sore or swollen mouth, lips or tongue
- severe pain in your stomach, with or without bloody diarrhoea, nausea and vomiting – these can be signs of pancreatitis
- difficulty or pain when you swallow, a sore throat, acid reflux, a smaller appetite or chest pain which gets worse when you eat – these could be signs of an inflamed food pipe (oesophagitis) or oesophageal ulcer
Serious allergic reaction
In rare cases, doxycycline can 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.
Other side effects
These are not all the side effects of doxycycline. For a full list see the leaflet inside your medicines packet.
You can report any suspected side effect using the Yellow Card safety scheme.