What Is Azithromycin? Uses, Dose and Side Effects

What Is Azithromycin? Uses, Dose and Side Effects

What azithromycin treats, the usual doses, side effects and interactions, and when UK prescribers choose it.

This is our general guide to the antibiotic azithromycin. For chlamydia specifically, see azithromycin for chlamydia or our chlamydia guide.

What azithromycin is and how it works

Azithromycin belongs to the macrolide family of antibiotics, alongside clarithromycin and erythromycin. It works by binding to the part of the bacterial cell that makes proteins (the ribosome), which stops the bacteria growing and multiplying.

Unlike many antibiotics, azithromycin is taken up into the body’s cells and tissues, where it stays at useful levels for several days after the last dose. That’s why its courses are so short, and why it works against bacteria that live inside cells, such as chlamydia. It’s a prescription-only medicine in the UK.

What azithromycin treats

Azithromycin is licensed in the UK for these bacterial infections in adults (product information):

• tonsillitis and throat infections caused by streptococcal bacteria;
• sinusitis and middle-ear infections caused by bacteria;
• pneumonia caught in the community, and flare-ups of chronic bronchitis;
• skin and soft-tissue infections;
• urethritis and cervicitis caused by chlamydia.

Specialists also use it in other ways, for example as a long-term low dose to reduce flare-ups in some people with COPD or bronchiectasis, and for some other sexually transmitted infections. Our guide to azithromycin for STIs explains its role in those.

Sore throats, sinusitis and chest infections

Although azithromycin is licensed for these infections, it isn’t usually the antibiotic UK doctors and pharmacists choose for them. Most are viral and get better without antibiotics. When an antibiotic is needed, NICE recommends other options first:

• Sore throat and tonsillitis: phenoxymethylpenicillin (penicillin V) for 5 to 10 days. If you’re allergic to penicillin, NICE recommends clarithromycin, or erythromycin in pregnancy (NG84). See our sore throat treatment page.
• Sinusitis: most cases clear on their own. If an antibiotic is needed, NICE recommends phenoxymethylpenicillin, with clarithromycin or doxycycline for people allergic to penicillin. See our sinusitis treatment page.
• Chest infections: pneumonia and flare-ups of COPD are usually treated with amoxicillin, doxycycline or clarithromycin, depending on the situation, after an assessment by a GP.

So if you’ve searched “azithromycin for tonsillitis”, the honest answer is that it can work, but a UK prescriber is more likely to offer penicillin, or clarithromycin if you’re allergic, and only if your throat infection is likely to be bacterial.

Doses and courses

The dose depends on the infection. These are the usual adult courses; your prescriber will tell you exactly what to take.

Azithromycin tablets can be taken with or without food; taking them just before a meal may make an upset stomach less likely. If you miss a dose, take it as soon as you remember, unless it’s nearly time for the next one, and never take two doses together to make up. Finish the whole course, even if you feel better.

Azithromycin for chlamydia

Azithromycin used to be the usual treatment for chlamydia. Since 2018, UK guidance has recommended doxycycline 100mg twice a day for 7 days instead, because it works slightly better for genital infection and clearly better for infection in the rectum. Azithromycin is now used for people who can’t take doxycycline, such as those allergic to tetracyclines, and in pregnancy, where doxycycline isn’t used.

After treatment, don’t have sex until you and your partner have both finished treatment, and until 7 days after your last azithromycin tablet. Partners from the last 6 months should be tested and treated, and under 25s should test again 2 to 6 months later. Our guide to azithromycin for chlamydia covers this in detail.

Side effects

Most people take azithromycin without problems. According to the product information:

• Very common (more than 1 in 10 people): diarrhoea.
• Common (up to 1 in 10): feeling sick, being sick, tummy pain and headache.
• Uncommon (up to 1 in 100) include dizziness, rash and itching, and thrush. If you feel dizzy, don’t drive or use machinery until it passes.

Who should take care with azithromycin

Tell your prescriber before taking azithromycin if you:

• have ever had an allergic reaction to azithromycin or another macrolide (such as clarithromycin or erythromycin);
• have a heart rhythm problem, including long QT syndrome, a slow heart rate or heart failure, or a family history of sudden death;
• have low potassium or magnesium levels;
• have liver or severe kidney problems;
• have myasthenia gravis, as azithromycin can make muscle weakness worse;
• are pregnant or breastfeeding: azithromycin can be used, but your doctor will weigh up the options.

Interactions, alcohol and contraception

Tell your prescriber about every medicine you take, including ones you’ve bought. Important interactions include (product information):

• medicines that affect heart rhythm, such as some medicines for abnormal heart rhythm, some antipsychotics and antidepressants, and hydroxychloroquine;
• warfarin: your INR may need checking more often;
• digoxin, colchicine and ciclosporin: their levels can rise, so you may need monitoring;
• ergotamine (used for migraine): shouldn’t be taken with azithromycin.

Alcohol doesn’t stop azithromycin working, but it can make sickness, diarrhoea and dizziness worse. Hormonal contraception such as the pill isn’t affected by azithromycin (FSRH), but severe vomiting or diarrhoea can stop the pill being absorbed: follow the missed-pill advice in your pill’s leaflet if this happens.

Finishing the course and antibiotic resistance

Bacteria resistant to azithromycin are now common in some infections: most gonorrhoea is no longer treated with it, and about two-thirds of Mycoplasma genitalium samples tested in England in 2025 showed resistance (UKHSA). Taking antibiotics only when a prescriber confirms you need them, taking the full course as directed, and never sharing tablets or keeping leftovers all help keep azithromycin working.

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.

Chlamydia treatment from Access Doctor

If you’ve tested positive for chlamydia, or a sexual partner has, and you’re 18 or over and not pregnant or breastfeeding, our pharmacist independent prescribers can assess you online. Doxycycline is the usual choice; azithromycin is for people who can’t take it.