How the UK’s first-choice chlamydia treatment works, how to take the 7-day course, and what to avoid while you take it.
Part of our Chlamydia condition guide.
Get urgent help first. Go to A&E or call 999 for sudden, severe pain in a testicle, or severe pain low in your tummy with a fever, fainting or any chance you could be pregnant. Contact NHS 111 (NHS 24 on 111 in Scotland) or your GP the same day for pelvic pain, pain during sex, bleeding between periods or after sex, or a fever with genital symptoms. Online treatment is not suitable in these situations.
Key fact: Doxycycline 100mg twice a day for 7 days is the first-choice treatment for chlamydia in UK guidance from the British Association for Sexual Health and HIV (BASHH). It treats genital, rectal and throat infection, and cures slightly more infections than the alternative, azithromycin.
Get Chlamydia Treatment Online
Access Doctor is a GPhC-registered pharmacy (#9011198). If you’ve tested positive for chlamydia, or a sexual partner has, a pharmacist independent prescriber reviews your online consultation and prescribes treatment if it’s suitable for you. Dispensed from our UK pharmacy. Approved before 3pm, Monday to Friday? Dispatched the same day, by Royal Mail Tracked 48, Tracked 24 or Special Delivery guaranteed by 1pm next working day: you choose.
Start Chlamydia Consultation →Adults only online. Access Doctor’s online chlamydia service is for adults aged 18 and over who are not pregnant or breastfeeding. If you’re under 18, pregnant or breastfeeding, an NHS sexual health clinic or your GP can test and treat you free and in confidence, and under 25s can also get help from Brook.
7 days
Course length: one capsule twice a day
14
Capsules in a full course
18+
Our online service is for adults
What is doxycycline?
Doxycycline is a tetracycline antibiotic. In the UK it is a prescription-only medicine, usually supplied as 100mg capsules or tablets. It is used for many bacterial infections, including some chest and skin infections, acne and malaria prevention, but in sexual health its main job is treating chlamydia.
Chlamydia is caused by the bacterium Chlamydia trachomatis. Most people who have it notice no symptoms, which is why many only find out from a routine test or because a partner has tested positive. Our guide to chlamydia symptoms, causes and treatment covers the infection itself.
Why doxycycline is the first choice
For many years a single dose of azithromycin was the usual chlamydia treatment in the UK. In 2018 BASHH changed its advice and made doxycycline the first choice, and its 2026 national guideline keeps it there. NICE’s clinical knowledge summary for GPs follows the same approach.
There are two main reasons. First, trials show doxycycline cures slightly more genital infections: a meta-analysis of randomised trials found about a 3% advantage over azithromycin. Second, the gap is much larger for chlamydia in the rectum, which is often found when people are tested at more than one site. Using less azithromycin also helps protect it against resistance in Mycoplasma genitalium, another sexually transmitted infection.
In short: doxycycline is preferred because it works slightly better for genital infection and clearly better for rectal infection. Azithromycin is still a good alternative for people who can’t take doxycycline.
How doxycycline works
Doxycycline stops bacteria making the proteins they need to grow and multiply, which gives your immune system the chance to clear the infection. Chlamydia lives inside the body’s cells, and doxycycline reaches good levels inside cells and tissues. The bacteria go through a life cycle lasting two to three days, so a 7-day course covers several cycles and gives the medicine time to clear them.
Dose and how to take it
The usual adult dose is 100mg twice a day for 7 days: 14 capsules in total, one in the morning and one in the evening, roughly 12 hours apart.
| Situation | Usual treatment |
|---|---|
| Genital chlamydia | Doxycycline 100mg twice a day for 7 days |
| Rectal chlamydia without symptoms | Doxycycline 100mg twice a day for 7 days |
| Throat chlamydia | Doxycycline 100mg twice a day for 7 days |
| Pain, discharge or bleeding from the bottom | See a sexual health clinic: some rectal infections need a longer course and extra tests |
| Pregnant or breastfeeding | Doxycycline isn’t usually used; see your GP, midwife or a sexual health clinic |
How to take doxycycline
- Swallow each capsule with a full glass of water, sitting or standing, and stay upright for at least 30 minutes afterwards. Don’t take it just before bed: if a capsule sticks in your food pipe it can cause painful irritation.
- With or without food. Food and milk don’t noticeably affect how much is absorbed, and taking it with a meal can help if it makes you feel sick.
- Keep indigestion remedies and some supplements apart. Don’t take antacids, or iron, zinc, calcium or magnesium supplements, within 2 hours of a dose, because they stop doxycycline being absorbed.
- Protect your skin from the sun. Doxycycline can make your skin burn more easily. Avoid strong sun and sunbeds and use a high-factor sunscreen during the course.
- Finish the course, even if you feel fine or any symptoms settle early.
If you miss a dose, take it as soon as you remember, unless it’s nearly time for your next one. Don’t take two doses together to make up for a missed one. If you miss several doses, tell your prescriber, because you may need a test after treatment.
Tested Positive for Chlamydia? Get Treated Online
Access Doctor is a GPhC-registered pharmacy (#9011198). If you’ve tested positive for chlamydia, or a sexual partner has, a pharmacist independent prescriber reviews your online consultation and prescribes treatment if it’s suitable for you. Dispensed from our UK pharmacy. Approved before 3pm, Monday to Friday? Dispatched the same day, by Royal Mail Tracked 48, Tracked 24 or Special Delivery guaranteed by 1pm next working day: you choose.
Start Chlamydia Consultation →Doxycycline vs azithromycin for chlamydia
| Doxycycline | Azithromycin | |
|---|---|---|
| Place in UK guidance | First choice | Alternative if doxycycline can’t be taken |
| Course | 100mg twice a day for 7 days | Usually 1g on day 1, then 500mg on days 2 and 3 |
| Genital infection | Cures slightly more | Cures most |
| Rectal infection | Preferred | Less effective; a test after treatment may be advised |
| Pregnancy | Not usually used | Used under the care of a midwife, GP or clinic |
| Main side effects | Feeling sick, sun sensitivity, food pipe irritation | Diarrhoea, feeling sick, tummy pain |
For most adults who aren’t pregnant, doxycycline is the right first choice. Azithromycin is used if you’re allergic to doxycycline or other tetracyclines, or can’t take them for another reason. Our azithromycin for chlamydia guide explains the alternative in detail.
Side effects of doxycycline
Most people take a 7-day course without problems. The product information lists these as common (affecting up to 1 in 10 people):
- feeling or being sick, or an upset stomach;
- headache;
- sensitivity to sunlight, or a rash.
Vaginal infections such as thrush are less common. Thrush can be treated with an antifungal from a pharmacy.
Stop taking doxycycline and get help if you have signs of a serious allergic reaction, such as swelling of the face, lips or throat, difficulty breathing or a widespread rash: call 999. Contact a doctor or NHS 111 if you have severe pain or difficulty swallowing, pain behind the breastbone, severe or bloody diarrhoea, or a severe headache with blurred vision.
Who should not take doxycycline
- Anyone allergic to doxycycline or another tetracycline, such as lymecycline or minocycline. Azithromycin is the usual alternative.
- Pregnant women. Doxycycline can affect a baby’s developing bones and teeth, and its product information says it shouldn’t be used in pregnancy. See our chlamydia in pregnancy guide.
- Breastfeeding mothers. Doxycycline passes into breast milk, and its product information advises against it while breastfeeding.
- Children under 12, because it can stain developing teeth.
Tell the prescriber if you have liver problems, myasthenia gravis or lupus, or if you take isotretinoin or another retinoid (these should not be combined with doxycycline), warfarin, medicines for epilepsy, indigestion remedies, or iron, zinc, calcium or magnesium supplements.
Contraception: doxycycline isn’t expected to make hormonal contraception less effective. If you vomit soon after taking a contraceptive pill, follow the missed-pill advice in your pill leaflet.
After treatment
1
Avoid sex until treatment is finished
Don’t have sex, including oral sex and sex with a condom, until you and your partner have both finished treatment and any symptoms have gone. If a partner takes azithromycin, they should wait until 7 days after their last tablet.
2
Tell recent partners
Anyone you’ve had sex with in the last 6 months should be tested and treated, even if they feel well. A sexual health clinic can tell partners for you without giving your name. See our partner notification guide.
3
Retest if you’re under 25
You don’t usually need a test to prove the treatment worked. A test after treatment is advised if you’re pregnant, missed doses or still have symptoms, and should be at least 3 weeks after finishing. If you’re under 25, have another test 2 to 6 months later, because catching it again is common.
4
Get a full STI check
Chlamydia often comes with other infections. Sexual health clinics advise testing for gonorrhoea, syphilis and HIV too. If symptoms haven’t cleared two weeks after finishing treatment, see a sexual health clinic or GP.
UK safety, support and free NHS options
Doxycycline and azithromycin are prescription-only medicines in the UK. Before anything is prescribed, a GPhC-registered pharmacist independent prescriber reviews your consultation, including your allergies and the other medicines you take. Always read the patient information leaflet in the pack. Never share antibiotics with anyone else, even a partner with the same infection, and don’t keep leftovers for another time: return unused tablets to a pharmacy.
If you think you’ve had a side effect from a medicine, tell your pharmacist or doctor. You can also report it to the MHRA through the Yellow Card scheme, which helps keep medicines safe for everyone.
NHS sexual health clinics test and treat chlamydia free of charge across the UK, and you don’t need a GP referral: use the NHS website in England, NHS inform in Scotland, Sexual Health Wales in Wales and nidirect in Northern Ireland to find one. Our private chlamydia treatment online service is an alternative for adults aged 18 and over.
If anything about how you got this infection doesn’t feel right, for example if sex wasn’t your choice or a partner pressures or controls you, you can talk to someone in confidence. See support, if you need it for free, confidential helplines. If you’re in immediate danger, call 999.
Frequently Asked Questions
Why is doxycycline used instead of azithromycin?
UK guidance from the British Association for Sexual Health and HIV (BASHH) has recommended doxycycline first since 2018, and its 2026 guideline keeps it as the first choice. Doxycycline cures slightly more genital infections and clearly more rectal infections than azithromycin. Azithromycin is still used for people who are allergic to doxycycline or can’t take it.
Can I take doxycycline with the contraceptive pill?
Yes. Doxycycline isn’t expected to make hormonal contraception less effective, so you don’t need extra contraception just because you’re taking it. If you vomit soon after taking your pill, follow the missed-pill advice in your pill leaflet.
What happens if I miss a dose of doxycycline?
Take it as soon as you remember, unless it’s nearly time for your next dose, then carry on as normal. Don’t take two doses together. If you miss several doses, tell your prescriber, because a course with gaps may not clear the infection and you may need a test afterwards.
Can I drink alcohol while taking doxycycline?
Moderate drinking is unlikely to stop doxycycline working, but it can make nausea worse. Heavy drinking can lower the level of doxycycline in your body, so it’s best to keep alcohol to a minimum until you’ve finished the course.
Do I need a test after taking doxycycline?
Not usually to check the treatment worked. A test is advised if you’re pregnant, if you missed doses or if your symptoms haven’t gone, and it should be at least 3 weeks after you finish. Separately, if you’re under 25, have another test 2 to 6 months later, because catching chlamydia again is common.
How quickly does doxycycline work for chlamydia?
It starts working from the first dose, and any symptoms usually begin to settle within a few days. The infection isn’t cleared until you’ve finished the full 7-day course, so keep taking it and avoid sex until you and your partner have both finished treatment.
Can I take doxycycline while breastfeeding?
Doxycycline passes into breast milk and its product information advises against it while breastfeeding. Our online service doesn’t treat chlamydia while you’re breastfeeding. Your GP or a sexual health clinic can prescribe a suitable alternative.
Chlamydia treatment from Access Doctor
If you’ve tested positive for chlamydia, or a sexual partner has, our pharmacist independent prescribers can assess you online. Doxycycline is the usual first choice; azithromycin is used if doxycycline isn’t suitable for you.
Antibiotic · Rx · usual first choice
Doxycycline 100mg capsules
7-day course: one capsule twice a day. Prescribed after an online consultation.
View product →Antibiotic · Rx · if you can’t take doxycycline
Azithromycin 500mg tablets
3-day course for people allergic to, or unable to take, doxycycline. Prescribed after an online consultation.
View product →References
- British Association for Sexual Health and HIV (BASHH). UK national guideline for the management of infection with Chlamydia trachomatis, 2026 (Saunders J, et al.). doi.org
- BASHH Clinical Effectiveness Group. Update on the treatment of Chlamydia trachomatis infection. September 2018. bashh.org
- NICE Clinical Knowledge Summaries. Chlamydia – uncomplicated genital. cks.nice.org.uk
- Kong FYS, Tabrizi SN, Law M, et al. Azithromycin versus doxycycline for the treatment of genital chlamydia infection: a meta-analysis of randomized controlled trials. Clin Infect Dis. 2014;59(2):193–205.
- Electronic Medicines Compendium. Doxycycline 100mg capsules: Summary of Product Characteristics. medicines.org.uk
- Faculty of Sexual and Reproductive Healthcare (FSRH). Drug interactions with hormonal contraception. fsrh.org
- NHS. Chlamydia: treatment. nhs.uk
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for diagnosis and treatment. In a medical emergency, call 999.