Azithromycin for Chlamydia: Dose, Safety and When It’s Used
When azithromycin is used instead of doxycycline, how to take the 3-day course, and what to expect afterwards.
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 is the first-choice chlamydia treatment in the UK. Azithromycin is the alternative for people who can’t take doxycycline, and is usually given as a 3-day course: 1g on day 1, then 500mg on days 2 and 3.
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.
3 days
Course used in NICE and NHS guidance
4
500mg tablets in a full course
7 days
After your last tablet before you have sex
What is azithromycin?
Azithromycin is a macrolide antibiotic, the same family as clarithromycin and erythromycin. In the UK it is a prescription-only medicine, usually supplied as 250mg or 500mg tablets. It stops bacteria making the proteins they need to survive. Chlamydia lives inside the body’s cells, and azithromycin builds up inside cells at much higher levels than in the blood, then stays there for several days after the last dose.
For azithromycin’s other uses, interactions and how it works in more detail, see our azithromycin: complete UK patient guide.
When azithromycin is used for chlamydia
Since 2018, UK guidance from the British Association for Sexual Health and HIV (BASHH) has recommended doxycycline as the first-choice treatment for chlamydia, and BASHH’s 2026 guideline keeps it there. Azithromycin is the alternative. It’s used:
- if you’re allergic to doxycycline or another tetracycline antibiotic, or can’t take it for another medical reason;
- in pregnancy and breastfeeding, where doxycycline isn’t usually used. This is arranged by your GP, midwife or a sexual health clinic, not our online service.
If you’ve read that azithromycin is the first choice, that advice is out of date. A single dose of azithromycin was the usual treatment until 2018. Doxycycline is now preferred because it works slightly better for genital infection and clearly better for rectal infection.
Dose and how to take it
The course used in NICE’s clinical knowledge summary and in current NHS pharmacy guidance is:
1
Day 1: 1g
Swallow two 500mg tablets together with water.
2
Day 2: 500mg
Take one 500mg tablet, at about the same time as the day before.
3
Day 3: 500mg
Take your last 500mg tablet. That completes the course.
You can take the tablets with or without food. Taking them just before a meal may help if you have a sensitive stomach. If you forget a dose, take it as soon as you remember, then carry on; don’t take two doses on the same day to catch up. If you’re sick soon after a dose, contact the pharmacy or your prescriber for advice.
Why a 3-day course? The product licence for azithromycin gives a single 1g dose for chlamydia, so the 3-day course is prescribed “off-label”, which is common, accepted practice in sexual health. BASHH’s newer 2026 guideline also allows a single 1g dose, and keeps the 3-day course as an option, particularly where another infection called Mycoplasma genitalium is a concern. Your prescriber will tell you exactly how to take your tablets.
Rectal chlamydia: azithromycin is less effective than doxycycline for infection in the rectum. If you’ve had anal sex, tell the prescriber, and see a sexual health clinic if you have pain, discharge or bleeding from your bottom, because some rectal infections need a longer course and extra tests.
Need Chlamydia Treatment? Start a Consultation
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 →Azithromycin vs doxycycline
Both antibiotics cure most chlamydia infections. Doxycycline is preferred because it cures slightly more genital infections and clearly more rectal ones; azithromycin is the alternative when doxycycline can’t be used. Our doxycycline for chlamydia guide compares the two side by side.
Side effects of azithromycin
Most people take azithromycin without serious problems. According to its product information:
- Very common (more than 1 in 10 people): diarrhoea.
- Common (up to 1 in 10 people): feeling or being sick, tummy pain and headache.
Get help: call 999 for signs of a serious allergic reaction, such as swelling of the face, lips or throat, difficulty breathing or a widespread rash. Contact a doctor or NHS 111 if you have a fast, pounding or irregular heartbeat or you faint, yellowing of your skin or eyes, or severe or bloody diarrhoea, even weeks after finishing the tablets.
Who should not take azithromycin
- Anyone allergic to azithromycin, erythromycin, clarithromycin or another macrolide. Doxycycline is the usual alternative.
- People with certain heart rhythm problems. Azithromycin can affect the heart’s rhythm (QT prolongation). Tell the prescriber if you have a heart rhythm problem, a slow heart rate or heart failure, low potassium or magnesium, or take other medicines that affect heart rhythm.
- People with significant liver disease, severe kidney problems or myasthenia gravis, who need extra care.
Tell the prescriber about all your medicines, especially warfarin, digoxin, colchicine, ciclosporin, statins and ergot medicines for migraine (which must not be taken with azithromycin).
After treatment
1
Avoid sex for 7 days after your last tablet
Don’t have sex, including oral sex and sex with a condom, until 7 days after your last tablet, and until your partner has also finished their treatment. The medicine keeps working for several days after the last dose.
2
Tell recent partners
Anyone you’ve had sex with in the last 6 months should be tested and treated. 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 is advised if your symptoms don’t clear, if you missed doses or if you’re pregnant, and may be advised after a rectal infection; it should be at least 3 weeks after treatment. If you’re under 25, have another test 2 to 6 months later.
4
See a clinic if symptoms persist
If symptoms haven’t cleared two weeks after treatment, see a sexual health clinic or GP. The usual reason is catching it again from an untreated partner, but another infection, such as gonorrhoea or Mycoplasma genitalium, may also need checking.
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
Is azithromycin still used to treat chlamydia in the UK?
Yes, but as the alternative rather than the first choice. UK guidance recommends doxycycline 100mg twice a day for 7 days first. Azithromycin is used when doxycycline can’t be taken, for example because of an allergy to tetracycline antibiotics, and in pregnancy under the care of a midwife, GP or sexual health clinic.
How do I take azithromycin for chlamydia?
The usual course in NICE and NHS guidance is 1g (two 500mg tablets) on day 1, then 500mg (one tablet) on days 2 and 3, with or without food. The product licence gives a single 1g dose instead, so the 3-day course is prescribed off-label, which is common practice in sexual health. Follow the instructions from your prescriber.
How long should I avoid sex after azithromycin?
Avoid all sex, including oral sex and sex with a condom, until 7 days after your last tablet, and until your partner has finished their treatment too. Azithromycin keeps working for several days after the last dose, and the infection isn’t cleared straight away.
Can I drink alcohol with azithromycin?
Azithromycin doesn’t react with alcohol in the way metronidazole does. Drinking can make nausea and diarrhoea worse, though, so it’s sensible to keep alcohol to a minimum while you’re taking it.
Do I need a test after azithromycin?
Not usually to check the treatment worked. A test is advised if your symptoms don’t clear, if you missed doses or if you’re pregnant, and may be advised after a rectal infection. It should be at least 3 weeks after treatment. If you’re under 25, have another test 2 to 6 months later, because catching chlamydia again is common.
Does azithromycin treat chlamydia in the throat or rectum?
Doxycycline is preferred for both, because it works better at these sites, especially the rectum. If you’ve had oral or anal sex, tell the prescriber, and see a sexual health clinic if you have pain, discharge or bleeding from your bottom.
Is azithromycin safe in pregnancy?
Azithromycin is one of the antibiotics UK guidance uses for chlamydia in pregnancy, but treatment in pregnancy needs a test afterwards and is arranged by your midwife, GP or a sexual health clinic. Our online service doesn’t treat chlamydia in pregnancy or while breastfeeding. See our chlamydia in pregnancy guide.
Should my partner take azithromycin too?
Your partner needs their own assessment, so don’t share your tablets. Most partners are offered doxycycline unless they can’t take it. A partner of someone with confirmed chlamydia can be treated straight away, at a sexual health clinic or, if they’re 18 or over and not pregnant, through an online service such as ours.
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
- Azithromycin for chlamydia: national patient group direction template, version 3.1, April 2026. communitypharmacy.org.uk
- Electronic Medicines Compendium. Azithromycin 500mg tablets: Summary of Product Characteristics. medicines.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.
- 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.