Doxycycline is an antibiotic.

It's used to treat infections such as chest infections, skin infections, rosacea, dental infections and sexually transmitted infections (STIs), as well as a lot of other rare infections.

It can also be used to prevent malaria if you're travelling abroad.

Doxycycline is available on prescription. It comes as capsules.

• For most infections, you'll start to feel better in a few days but it is important to finish the course of medicine.
• The most common side effects of doxycycline are headaches, feeling or being sick. It can also make your skin sensitive to the sun.
• Doxycycline can affect growing teeth so it's not prescribed for children under 12 years old or given to pregnant and breastfeeding women.
• Do not drink alcohol while taking doxycycline. There are also some common medicines you should not mix with it.
• Doxycycline can also be called by the brand name Vibramycin-D.

Doxycycline can be taken by adults and children over 12 years old. Doxycycline is not usually recommended in pregnancy or when breastfeeding.

It isn't suitable for some people. To make sure this medicine is safe for you, tell your doctor if you have:

• ever had an allergic reaction to doxycycline or any other medicine in the past
• kidney problems
• liver problems
• an inflamed food pipe (oesophagitis)
• lupus, an autoimmune disease
• myasthenia gravis, an illness that causes severe muscle wasting

Your dose of doxycycline depends on why you are taking it.

The usual dose is 100mg to 200mg once or twice a day. If you're taking doxycycline more than once a day, try to space your doses evenly throughout the day. If you take it twice a day, this could be first thing in the morning, and in the evening.

For preventing malaria, you'll take 100mg once a day, usually in the morning. You should start taking doxycycline 1 or 2 days before going to an area where there is malaria. Carry on for 4 weeks after leaving the area. Check with your doctor or pharmacist that doxycycline is the best medicine to prevent malaria in the country you are travelling to.

How to take it

Always swallow your doxycycline capsule whole and have it with a full glass of water (a medium sized glass - 200ml).

You can take this medicine with or without food. However you're less likely to feel sick if you have it with food.

It's important to take doxycycline while you're in an upright position. You can be sitting, standing or walking. This will stop the medicine irritating your food pipe or stomach.

What if I forget to take it?

If you forget to take a dose, take it as soon as you remember, unless it's nearly time for your next dose. In this case, just leave out the missed dose and take your next dose as normal.

Never take 2 doses at the same time. Never take an extra dose to make up for a forgotten one.

If you often forget doses, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to remember your medicines.

What if I take too much?

Accidentally taking an extra dose of doxycycline is unlikely to harm you.

Speak to your pharmacist or doctor if you're worried or you take more than 1 extra dose.

Like all medicines, doxycycline can cause side effects, although not everyone gets them.

Common side effects

These common side effects happen in around 1 in 10 people. Keep taking the medicine, but talk to your doctor or pharmacist if these side effects bother you or don't go away:

• headaches
• feeling or being sick (nausea or vomiting)
• being sensitive to sunlight

Serious side effects

Serious side effects are rare and happen in less than 1 in 1,000 people.

Call a doctor straight away if you get:

• bruising or bleeding you can't explain (including nosebleeds), a sore throat, a high temperature (38C or above) and you feel 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 you should also speak to a doctor
• ringing or buzzing in your ears
• pale poo with dark pee, yellow skin or the whites of your eyes go yellow - this could be a sign of liver problems
• joint or muscle pain that has started since you began taking doxycycline
• severe headaches, vomiting and problems with your vision - these could be signs of pressure around your brain (intracranial hypertension)
• a fingernail 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

Allergic reactions to doxycycline are common and occur in more than 1 in 100 people.

In rare cases, doxycycline can cause a serious allergic reaction anaphylaxis.

These are not all the side effects of doxycycline. For a full list see the leaflet inside your medicines packet.

What to do about:

• headaches - make sure you rest and drink plenty of fluids. Everyday painkillers, such as paracetamol and ibuprofen, are safe to take with doxycycline.
• feeling or being sick (nausea or vomitting) - stick to simple meals and do not eat rich or spicy food. It might help to take your doxycycline after a meal or snack but avoid dairy products like milk, cheese and yoghurt. Dairy products can stop your body absorbing your medicine properly. If you are being sick, drink plenty of fluids, such as water or squash, to avoid dehydration. Signs of dehydration include peeing less than usual or having strong-smelling pee. Do not take any medicines to treat vomiting without speaking to a pharmacist or doctor.
• sensitivity to sunlight - when you go outside, wear sunglasses and clothes that cover you up. Put sunscreen or sunblock on your skin - with a sun protection factor (SPF) of at least 15 (if you have fair skin, you may need a much higher number than this). Also use a sunscreen product for your lips. Do not use sunlamps or tanning beds. If you get sunburn, there are things you can do to treat your symptoms.

Doxycycline is not normally recommended in pregnancy or when breastfeeding.

For more information about how doxycycline can affect you and your baby during pregnancy visit the Best Use of Medicines in Pregnancy (BUMPS) website.

There are some medicines that don't mix well with doxycycline.

Tell your doctor if you're taking these medicines before you start taking doxycycline:

• indigestion remedies (antacids)
• supplements which contain aluminium, bismuth, calcium, magnesium or zinc
• stomach ulcer medicines that contain bismuth
• iron supplements
• other antibiotics
• acne medicines which contain vitamin A, such as isotretinoin
• a blood thinner called warfarin
• medicines for epilepsy, such as phenytoin or carbamazepine
• ciclosporin, a medicine to damp down your immune system

Typhoid vaccine given by mouth may not work properly if you're taking doxycycline. If you need a typhoid vaccine while taking doxycycline, your doctor or nurse will give it by injection.

Mixing doxycycline with herbal remedies and supplements

There are no known problems with taking herbal remedies and supplements with doxycycline.