1. About doxycycline
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.
 
2. Key facts
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.
 
3. Who can and can't take doxycycline
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
 
4. How and when to take it
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. 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.
 
5. Side effects
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
 
6. 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
 
7. Pregnancy and breastfeeding
Doxycycline is not normally recommended in pregnancy or when breastfeeding.
 
8. Cautions with other medicines
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.