Azithromycin for Chlamydia UK: Dosing, Safety & Getting It Online
Key fact: Following updated BASHH 2025 guidance, doxycycline 100 mg twice daily for 7 days is now the first-line treatment for urogenital chlamydia in the UK. Azithromycin 1 g as a single dose remains a clinically effective second-line option — particularly when doxycycline is contraindicated or tolerance is a concern.
1 g
Standard single-dose azithromycin for uncomplicated urogenital chlamydia
~97%
Cure rate for genital chlamydia with a single 1 g azithromycin dose
7 days
Time to abstain from sex after azithromycin treatment
What Is Azithromycin?
Azithromycin is a macrolide antibiotic available in the UK under the brand name Zithromax and in generic form as 250 mg and 500 mg tablets or capsules. It is a prescription-only medicine (POM) used to treat a range of bacterial infections, with particular effectiveness against intracellular organisms — bacteria that live and replicate inside human cells, such as Chlamydia trachomatis.
Within the chlamydia cluster, azithromycin occupies a clear and important role: it is the preferred second-line treatment and the recommended option when doxycycline is contraindicated — for example, in pregnancy (where it may be used under specialist guidance), or in patients with a documented tetracycline allergy. Its single-dose format also makes it valuable in clinical situations where adherence to a multi-day course cannot be assured.
How Does Azithromycin Work?
Azithromycin is a macrolide antibiotic that inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit, blocking bacterial growth and replication. Its long tissue half-life allows the single 1g dose to maintain therapeutic concentrations for several days.
For a full pharmacology breakdown including tissue penetration, resistance mechanisms and drug interactions: Azithromycin antibiotic: complete UK patient guide →
Current BASHH 2025 Position
The British Association for Sexual Health and HIV (BASHH) updated its chlamydia management guidelines in 2025 following a review of comparative clinical trial data. The headline change is that doxycycline 100 mg twice daily for 7 days is now the recommended first-line treatment for urogenital chlamydia in adults who are not pregnant. Evidence from network meta-analyses, including data from the pivotal REACT trial, found doxycycline demonstrated marginally superior microbiological cure rates and better efficacy for rectal chlamydia compared with single-dose azithromycin.
Important update: If you have previously read that azithromycin is the first-line treatment for chlamydia, this information is now out of date. BASHH 2025 guidelines recommend doxycycline as first-line. Azithromycin remains a clinically important second-line option. Always follow current prescriber guidance.
Azithromycin retains a well-defined role in BASHH 2025 guidance. It is recommended:
- As a second-line option for uncomplicated urogenital chlamydia when doxycycline is contraindicated or not tolerated
- In pregnancy: azithromycin 1 g stat may be used when other options are not appropriate — though specialist or obstetric input should be sought, and a test of cure is required at 5–6 weeks post-treatment
- For non-specific urethritis (NSU) without confirmed chlamydia, as a single 1 g dose
- Where adherence to a 7-day course is unlikely to be achievable
Dosing for Chlamydia
For uncomplicated urogenital chlamydia in non-pregnant adults, the azithromycin regimen is a single oral dose of 1 g (two 500 mg tablets taken together), taken on an empty stomach or with a light meal. The single-dose format is one of azithromycin’s most clinically practical features: adherence is guaranteed in supervised settings, there is no risk of course incompletion, and the prolonged tissue half-life ensures sustained therapeutic activity.
| Indication | Regimen | Guideline source |
|---|---|---|
| Uncomplicated urogenital chlamydia (second-line) | Azithromycin 1 g orally as a single dose | BASHH 2025 |
| Chlamydia in pregnancy (specialist guidance required) | Azithromycin 1 g orally as a single dose; test of cure at 5–6 weeks | BASHH 2025 / RCOG |
| Non-specific urethritis (NSU) | Azithromycin 1 g stat or 500 mg on day 1 then 250 mg days 2–5 | BASHH 2015 (NSU guideline) |
| Rectal chlamydia | Doxycycline preferred (superior cure rate); azithromycin not recommended for rectal infection per BASHH 2025 | BASHH 2025 |
Rectal chlamydia: Azithromycin single-dose treatment has been shown to have lower microbiological cure rates for rectal chlamydia compared with urogenital chlamydia. BASHH 2025 guidance recommends doxycycline for rectal infection. Inform your prescriber of your sexual practices so the correct treatment can be selected.
Need Azithromycin for Chlamydia? Start a Private Consultation
Access Doctor is a GPhC-registered online pharmacy (#9011198). Our pharmacist independent prescribers can assess your suitability for azithromycin or doxycycline and issue a prescription the same day. Discreet packaging, next-day delivery across the UK.
Start Chlamydia Consultation →Azithromycin vs Doxycycline for Chlamydia
Following the BASHH 2025 update, doxycycline 100mg twice daily for 7 days is first-line for urogenital chlamydia. Azithromycin 1g single dose is second-line — appropriate where doxycycline is contraindicated (pregnancy, allergy) or where adherence to a 7-day course is a clinical concern. Both agents achieve high cure rates for uncomplicated infection.
Full comparison: Doxycycline vs azithromycin for chlamydia — complete comparison →
Side Effects of Azithromycin
Azithromycin is generally well tolerated, particularly at the 1 g single dose used for chlamydia. The most commonly reported side effects are gastrointestinal and are usually mild and transient.
Common side effects (affecting more than 1 in 10 patients)
- Nausea — the most frequently reported effect; taking the dose with a small amount of food can help
- Diarrhoea or loose stools — typically resolves within 24–48 hours
- Abdominal discomfort or cramping
Less common side effects (affecting 1 in 10 to 1 in 100 patients)
- Headache
- Dizziness
- Altered or metallic taste
- Skin rash or mild itching
Rare but serious — QT prolongation: Azithromycin can affect cardiac electrical conduction in rare cases, potentially causing QT interval prolongation. This risk is most relevant in people with pre-existing heart conditions, electrolyte abnormalities (low potassium or magnesium), or those taking other QT-prolonging medicines. Report any new palpitations, dizziness, or irregular heartbeat to a prescriber immediately.
Allergic reaction: Stop azithromycin immediately and seek medical attention if you develop hives, facial swelling, difficulty breathing, or a widespread rash. Severe allergic reactions to macrolides, though uncommon, require prompt treatment.
Who Should Not Take Azithromycin?
Azithromycin is contraindicated in the following circumstances. A clinical consultation is essential before prescribing to identify any relevant risk factors.
- Known allergy to azithromycin or any macrolide antibiotic (erythromycin, clarithromycin). Macrolide hypersensitivity is a hard contraindication; doxycycline is the alternative if no tetracycline allergy exists.
- Significant hepatic impairment. Azithromycin is hepatically metabolised; severe liver disease can impair clearance and increase toxicity risk.
- Myasthenia gravis. Azithromycin may exacerbate neuromuscular blockade in patients with this condition. Alternative antibiotics should be used.
- Concurrent use of QT-prolonging medicines (e.g., amiodarone, certain antipsychotics, some antifungals). Combination with azithromycin increases the risk of dangerous arrhythmia.
- Pre-existing QT prolongation or cardiac arrhythmia (including bradycardia, hypokalaemia, hypomagnesaemia).
- Pregnancy (relative — requires specialist input). Azithromycin is not a routine choice in pregnancy but may be used under obstetric guidance when other options are unsuitable. See our chlamydia in pregnancy guide.
Drug interactions to declare to your prescriber
Always inform your prescriber of all current medications, including over-the-counter products. Key interactions include antacids containing aluminium or magnesium (reduce absorption — take azithromycin 1 hour before or 2 hours after), warfarin (azithromycin may increase INR; monitoring advised), digoxin, ergot alkaloids, and ciclosporin.
After Treatment: What to Do
Taking your azithromycin dose is only the first step. Following these post-treatment steps is essential to confirm the infection has cleared and to prevent reinfection or onward transmission.
1
Abstain from sex for 7 days
Do not have any sexual contact — including oral sex — for at least 7 days after taking your dose. This applies even if your symptoms have resolved. The infection may still be present during this window and you could pass it on to a partner.
2
Notify sexual partners
All recent sexual partners should be informed and offered testing and treatment. The standard lookback period is the past 6 months, or to your last known contact if sooner. Partners who are not treated may reinfect you. See our partner notification guide.
3
Retest at 3 months
BASHH guidelines recommend retesting for chlamydia 3 months after treatment, regardless of symptoms. This is to detect reinfection (which is common) rather than treatment failure. Routine test of cure is not needed for non-pregnant patients on azithromycin or doxycycline, except in pregnancy or rectal infection.
4
Return if symptoms persist
If symptoms (discharge, pain, burning) persist beyond 7–14 days after treatment, contact your prescriber. This may indicate treatment failure (rare), reinfection, or a co-existing STI such as gonorrhoea or NSU, which requires separate management.
Second-line treatment
Azithromycin 1 g
Single-dose treatment for uncomplicated urogenital chlamydia. Prescription following clinical assessment. Discreet delivery.
View azithromycin →First-line treatment (BASHH 2025)
Doxycycline 100 mg
100 mg twice daily for 7 days. Current first-line treatment per BASHH 2025 guidelines. Prescription following clinical assessment.
View doxycycline →Getting Azithromycin Online in the UK
Azithromycin is a prescription-only medicine in the UK. It cannot legally be sold without a valid prescription issued by a registered prescriber following an appropriate clinical assessment. Online pharmacies and telemedicine services registered with the General Pharmaceutical Council (GPhC) can legally conduct consultations and issue prescriptions remotely.
When using an online prescribing service, a legitimate provider will:
- Ask about your symptoms and sexual history
- Screen for contraindications (allergies, cardiac history, current medicines, pregnancy status)
- Confirm your diagnosis is consistent with chlamydia or another relevant indication
- Issue a prescription through a GPhC-registered pharmacist independent prescriber
- Provide post-treatment advice on abstinence, partner notification, and retesting
Start Your Online Chlamydia Consultation
Access Doctor is a GPhC-registered pharmacy (#9011198). Complete a short online assessment — our pharmacist independent prescribers will review your case, select the most appropriate antibiotic for your circumstances, and arrange same-day dispatch with discreet, next-day delivery.
Start Consultation →Frequently Asked Questions about Azithromycin for Chlamydia
Is azithromycin still used to treat chlamydia in the UK?
Yes. Azithromycin remains a recommended treatment for uncomplicated urogenital chlamydia in the UK. However, following BASHH’s 2025 guidance update, it is now classified as the second-line option. Doxycycline 100 mg twice daily for 7 days is the current first-line treatment. Azithromycin is used when doxycycline is contraindicated, not tolerated, or when single-dose compliance is a priority.
How long does azithromycin take to clear chlamydia?
After a single 1 g dose, azithromycin maintains therapeutic tissue concentrations for approximately 7–10 days. Most patients will have microbiologically clear infection within 7 days. You should abstain from sex for at least 7 days after taking your dose regardless of symptom resolution to avoid transmitting the infection.
Can I drink alcohol after taking azithromycin?
Unlike metronidazole, azithromycin does not cause a dangerous interaction with alcohol. However, alcohol can worsen nausea — the most common azithromycin side effect — and may impair recovery from infection. Moderate intake is unlikely to affect the antibiotic’s efficacy, but abstaining while unwell is advisable.
Do I need a test of cure after azithromycin treatment?
For non-pregnant patients with urogenital chlamydia treated with azithromycin or doxycycline, a routine test of cure is not recommended by BASHH guidelines. You should retest at 3 months to detect any reinfection. Test of cure is recommended in pregnancy (at 5–6 weeks post-treatment) and for rectal chlamydia treated with azithromycin (where cure rates are lower).
Can azithromycin treat chlamydia in the throat?
Pharyngeal (throat) chlamydia is uncommon but documented. Data on azithromycin cure rates for pharyngeal chlamydia are limited. BASHH guidance recommends informing your prescriber of the site of infection, as this affects treatment selection and the need for test of cure. Doxycycline is generally preferred for extra-genital infection.
What happens if azithromycin does not clear the chlamydia?
True azithromycin treatment failure is uncommon for urogenital chlamydia. If symptoms persist after 7–14 days, the most likely explanation is reinfection from an untreated partner rather than antibiotic resistance. Return to your prescriber for a repeat NAAT test, ensure all recent partners have been tested and treated, and discuss switching to doxycycline if azithromycin was the initial treatment.
Is azithromycin safe in pregnancy?
Azithromycin is not routinely recommended in pregnancy as first-choice therapy, but it may be used under specialist or obstetric guidance when other options are unsuitable. Doxycycline is contraindicated in pregnancy. If you are pregnant and diagnosed with chlamydia, your prescriber will discuss the most appropriate option — typically azithromycin 1 g stat or erythromycin — and arrange a test of cure.
Can I take azithromycin with food?
Yes. Taking azithromycin with a small meal or snack can reduce the likelihood of nausea, which is the most common side effect. Avoid taking it immediately after a large high-fat meal as this may slightly reduce absorption. Antacids containing aluminium or magnesium should be taken at least 1 hour before or 2 hours after your azithromycin dose.
Should my partner also take azithromycin?
Your recent sexual partners should be tested and, if indicated, treated. Your prescriber can advise on partner notification. Partners may be offered azithromycin or doxycycline based on their individual circumstances after their own clinical assessment. Expedited partner therapy (EPT) — providing medication for untested partners — is not standard practice in the UK, but partners can be referred to sexual health clinics or online services for rapid assessment.
References
- British Association for Sexual Health and HIV (BASHH). United Kingdom National Guideline for the Management of Infection with Chlamydia trachomatis. Updated 2025. Available at: www.bashh.org/guidelines
- NICE. Chlamydia — uncomplicated genital. Clinical Knowledge Summary. 2025. Available at: 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.
- Manhart LE, Broad JM, Golden MR. Mycoplasma genitalium: should we treat and how? Clin Infect Dis. 2011;53(Suppl 3):S129–S142.
- Electronic Medicines Compendium (eMC). Azithromycin 500 mg film-coated tablets — Summary of Product Characteristics. Available at: www.medicines.org.uk/emc
- BNF. Azithromycin. British National Formulary. 2025. Available at: bnf.nice.org.uk
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Azithromycin is a prescription-only medicine (POM) in the UK; it must not be taken without a valid prescription issued following a clinical assessment. Always consult a qualified healthcare professional before starting any antibiotic treatment. In a medical emergency, call 999.