Azithromycin for Chlamydia

Azithromycin is a macrolide antibiotic that stops chlamydia bacteria making the proteins they need to survive and multiply. Chlamydia lives inside the body’s cells, and azithromycin builds up inside cells at much higher levels than in the blood. It stays there for several days after the last dose, which is why a short course works.

UK guidance from the British Association for Sexual Health and HIV (BASHH) recommends doxycycline first. Trials show it cures chlamydia slightly more reliably, and it works noticeably better for rectal infection. Azithromycin can also encourage resistance in Mycoplasma genitalium, another sexually transmitted infection, which the product information itself warns about. Azithromycin remains a good alternative for people who can’t take doxycycline.

Mainly when someone is allergic to doxycycline or other tetracycline antibiotics, or can’t take them for another medical reason. The prescriber decides after reviewing your consultation. Azithromycin is also used in pregnancy, but our online service doesn’t treat pregnant or breastfeeding women; your GP, midwife or a sexual health clinic will arrange that.

A 3-day course: 1g (two 500mg tablets) on day 1, then 500mg (one tablet) once a day on days 2 and 3, with or without food. This is the course in NICE and NHS guidance. The product licence gives a single 1g dose instead, so the 3-day course is prescribed off-label. That’s common practice in sexual health.

Avoid all sex, including oral sex and sex with a condom, until 7 days after your last tablet. The medicine keeps working for several days, and the infection isn’t cleared straight away. Your partner should also have finished their treatment, and if they took azithromycin, waited until 7 days after their last tablet, before you have sex again.

Diarrhoea is the most common, affecting more than 1 in 10 people. Headache, feeling sick and tummy pain are also common. Rarely, azithromycin can affect heart rhythm, especially in people with existing heart rhythm problems, low potassium or magnesium, or who take certain other medicines, so tell the prescriber about these. Severe or bloody diarrhoea, even weeks later, needs prompt medical advice.

Yes. Most people with chlamydia have no symptoms, so partners may have it without knowing. Anyone you’ve had sex with in the last 6 months should be tested and treated. If your last partner was longer ago than that, tell them too. If you’d rather not tell a partner yourself, or it doesn’t feel safe, a sexual health clinic can contact them for you without giving your name.

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 if you had a rectal infection. It should be at least 3 weeks after treatment, or it can pick up leftover traces of the bacteria. If you’re under 25, have another test 2 to 6 months later, because catching it again is common.

Not through our online service. Azithromycin is one of the antibiotics used for chlamydia in pregnancy, but treatment in pregnancy needs a follow-up test and specialist care. If you’re breastfeeding, the prescriber needs to weigh up the effects on your baby. Please contact your GP, midwife or a sexual health clinic. Read more in our chlamydia in pregnancy guide.

See a sexual health clinic or GP if symptoms haven’t cleared two weeks after treatment, or if they come back. The most common reason is catching it again from an untreated partner. Another infection, such as Mycoplasma genitalium, gonorrhoea or trichomoniasis, may also have been missed. Get help sooner if you develop pelvic pain, testicular pain or a fever.