Doxycycline for Chlamydia UK: First-Line Treatment Guide
Key fact: Doxycycline 100 mg twice daily for 7 days is the current first-line treatment for urogenital and rectal chlamydia in the UK, as recommended by BASHH’s updated 2025 guidelines. It is highly effective, well tolerated, and the preferred option for most non-pregnant adults.
98–99%
Cure rate for urogenital chlamydia with a full 7-day doxycycline course
7 days
Duration of treatment — 100 mg twice daily, 14 tablets total
~100%
Cure rate for rectal chlamydia (superior to azithromycin single dose)
What Is Doxycycline?
Doxycycline is a broad-spectrum tetracycline antibiotic available in the UK as 100 mg capsules or tablets (brand names include Vibramycin-D and generic forms). It is a prescription-only medicine (POM) used across a wide range of bacterial infections, including urinary tract infections, skin and soft tissue infections, respiratory infections, Lyme disease, and malaria prophylaxis.
In sexual health, doxycycline holds a central role. Since BASHH’s 2025 guideline update, it is the designated first-line antibiotic for uncomplicated urogenital and rectal chlamydia in the UK — superseding azithromycin, which had held that position for many years. Its superior efficacy at certain anatomical sites, combined with well-established safety data, underpins this change in practice.
Why Doxycycline Is Now First-Line (BASHH 2025)
For many years, azithromycin 1 g as a single dose was the UK’s default first-line treatment for chlamydia — largely on the strength of its convenience and adequate efficacy for uncomplicated urogenital infection. However, accumulating evidence from randomised controlled trials and network meta-analyses began to reveal a clinically important gap: azithromycin performed significantly worse than doxycycline for rectal chlamydia, with cure rates of approximately 83% compared to near 100% for doxycycline.
As the profile of chlamydia patients presenting to sexual health services evolved — with rectal infection increasingly identified through expanded anatomical site testing — the limitations of a single-dose regimen that left one in six rectal infections uncured became untenable. BASHH’s 2025 review, incorporating data from the pivotal REACT trial and subsequent analyses, formalised the switch. Doxycycline is now recommended first-line for all anatomical sites of uncomplicated chlamydial infection in non-pregnant adults.
Clinical significance: The shift to doxycycline as first-line is not merely theoretical. For urogenital infection the difference in cure rates is modest (~1–2%). For rectal chlamydia, the difference is substantial — doxycycline achieves near-complete cure while azithromycin leaves approximately 1 in 6 rectal infections untreated. Knowing your site of infection matters when choosing treatment.
How Does Doxycycline Work?
Doxycycline is a bacteriostatic antibiotic that works by binding reversibly to the 30S ribosomal subunit of bacterial cells, blocking the attachment of aminoacyl-tRNA to the mRNA-ribosome complex. This interrupts the elongation of the peptide chain during protein synthesis — without which bacteria cannot grow or replicate.
Critically for chlamydia treatment, doxycycline achieves excellent penetration into tissues and intracellular compartments. Chlamydia trachomatis is an obligate intracellular pathogen — it replicates only inside host cells. Doxycycline’s ability to penetrate cellular membranes and reach therapeutic concentrations within the intracellular vacuoles where chlamydia replicates is essential to its efficacy. The 7-day course sustains inhibitory concentrations throughout the chlamydial developmental cycle (which takes 48–72 hours per generation), ensuring complete bacterial clearance.
Class: Tetracycline antibiotic
Blocks bacterial protein synthesis at the 30S ribosomal subunit. Bacteriostatic — halts growth, allowing immune clearance. Excellent intracellular and tissue penetration.
Why 7 days?
The chlamydial developmental cycle takes 48–72 hours. A 7-day course covers multiple replication cycles, ensuring elimination of all intracellular organisms at the site of infection.
Dosing and How to Take It
The standard doxycycline regimen for uncomplicated urogenital or rectal chlamydia in non-pregnant adults is 100 mg twice daily for 7 days. This is 14 tablets or capsules in total, taken approximately 12 hours apart — for example, one in the morning and one in the evening.
| Indication | Regimen | Guideline |
|---|---|---|
| Uncomplicated urogenital chlamydia | 100 mg twice daily for 7 days | BASHH 2025 — first-line |
| Rectal chlamydia | 100 mg twice daily for 7 days | BASHH 2025 — first-line (superior to azithromycin) |
| Pharyngeal chlamydia | 100 mg twice daily for 7 days | BASHH 2025 — preferred option; test of cure recommended |
| Chlamydia in pregnancy | Contraindicated. Use azithromycin, erythromycin, or amoxicillin under specialist guidance | BASHH 2025 / RCOG |
How to take doxycycline correctly
- Take with food or a full glass of water to reduce gastric irritation, the most common reason for stopping early.
- Remain upright for at least 30 minutes after each dose. Doxycycline can cause oesophageal irritation or even oesophageal ulceration if it dissolves in the oesophagus rather than the stomach — particularly if taken lying down or with insufficient water.
- Space doses 12 hours apart — consistency helps maintain therapeutic blood levels throughout the 7 days.
- Avoid dairy products, antacids, iron supplements, and calcium-containing preparations within 2–3 hours of a dose. Divalent cations (calcium, magnesium, iron, aluminium) bind doxycycline in the gut and significantly reduce absorption.
- Use effective sun protection throughout the course. Doxycycline causes photosensitivity — the skin becomes more susceptible to sunburn, even on cloudy days.
- Complete the full 7-day course even if you feel better or your symptoms resolve. Stopping early risks leaving the infection partially treated and may contribute to resistance.
Do not lie down after taking doxycycline. Taking doxycycline with insufficient water or immediately before lying down is the most preventable cause of oesophageal ulceration — a painful complication. Always take your dose with a full glass of water and stay upright for at least 30 minutes.
Get Doxycycline for Chlamydia Online — Same-Day Consultation
Access Doctor is a GPhC-registered pharmacy (#9011198). Complete a short online assessment and receive a prescription for doxycycline or azithromycin from our pharmacist independent prescribers. Discreet packaging, next-day delivery across the UK.
Start Chlamydia Consultation →Doxycycline vs Azithromycin for Chlamydia
Both antibiotics are effective against Chlamydia trachomatis and both remain on the BASHH 2025 treatment list. The choice between them is guided by site of infection, individual patient factors, and tolerability.
| Factor | Doxycycline | Azithromycin |
|---|---|---|
| BASHH 2025 status | First-line | Second-line / when doxycycline contraindicated |
| Dose schedule | 100 mg twice daily × 7 days (14 tablets) | 1 g single dose (2 tablets) |
| Urogenital cure rate | ~98–99% | ~97–98% |
| Rectal cure rate | ~100% — clearly superior | ~83% — not recommended for rectal infection |
| Safe in pregnancy? | No — contraindicated | May be used under specialist guidance |
| Adherence requirement | Requires completing 7-day course | Single dose — adherence guaranteed |
| Main side effects | GI upset, photosensitivity, oesophageal irritation | Nausea, diarrhoea, abdominal discomfort |
For most non-pregnant adults, doxycycline is the right first choice. Azithromycin remains the clinically appropriate option when doxycycline is contraindicated — for example in pregnancy, confirmed tetracycline allergy, or where single-dose compliance is a clear clinical priority. See our full azithromycin guide for detail on the second-line option.
Side Effects of Doxycycline
Doxycycline is generally well tolerated when taken correctly. The most clinically relevant side effects for a 7-day chlamydia course are gastrointestinal and photosensitivity-related.
Common (affecting more than 1 in 10)
- Nausea, vomiting, or diarrhoea — the most frequently reported side effects. Taking with food substantially reduces gastrointestinal discomfort without meaningfully affecting absorption.
- Photosensitivity — increased sensitivity of the skin to sunlight. Apply SPF 30+ sunscreen during the course and for several days after completing it, particularly in summer or bright conditions.
- Oesophageal irritation — a burning sensation in the chest or difficulty swallowing, caused by the tablet dissolving in the oesophagus. Prevented by taking with a full glass of water and remaining upright for 30 minutes after each dose.
Less common
- Headache and dizziness
- Skin rash or mild itching
- Vaginal thrush (candidal vaginitis) — antibiotics can disrupt normal vaginal flora. Treat with an over-the-counter antifungal (clotrimazole) if this occurs.
Rare but serious — oesophageal ulceration: Doxycycline can cause oesophageal ulceration if it lodges in the oesophagus rather than reaching the stomach. This is almost entirely preventable by taking each dose with a full glass (200 ml minimum) of water and staying upright for at least 30 minutes. If you experience severe chest pain, difficulty swallowing, or feel as though a tablet is stuck, seek medical attention.
Who Should Not Take Doxycycline?
- Pregnancy. Doxycycline is classified as pregnancy category D. It crosses the placenta and can cause discolouration of foetal teeth and impaired bone growth. It is absolutely contraindicated in pregnancy. See our chlamydia in pregnancy guide for safe treatment alternatives.
- Children under 12 years (or under 8 in some guidelines). Tetracyclines cause permanent discolouration of developing teeth and may impair bone growth.
- Known allergy to doxycycline or any tetracycline antibiotic (tetracycline, minocycline, lymecycline). This is a hard contraindication; azithromycin or erythromycin are alternatives.
- Severe hepatic impairment. Doxycycline is primarily eliminated by the liver; significant hepatic disease increases drug accumulation and toxicity risk.
- Myasthenia gravis — like other antibiotics, doxycycline can potentially exacerbate neuromuscular blockade.
Important drug interactions
Declare all current medications to your prescriber. Key interactions include antacids, iron preparations, dairy products and calcium (reduce absorption — take 2–3 hours apart), oral retinoids such as isotretinoin (increased risk of intracranial hypertension — combination contraindicated), warfarin (doxycycline may increase anticoagulant effect; INR monitoring required), oral contraceptive pill (doxycycline does not significantly affect combined OCP efficacy, but patients should follow standard missed-pill guidance if vomiting occurs), and ciclosporin.
Making It Through the Full 7-Day Course
The most important predictor of treatment success with doxycycline is completing the full 7-day course. Clinical data consistently show that premature cessation — stopping after 3–5 days when symptoms resolve — risks treatment failure and may contribute to antibiotic resistance.
1
Set twice-daily alarms
Take one 100 mg tablet in the morning and one in the evening, approximately 12 hours apart. Setting alarms on your phone for the same time each day removes the risk of forgetting a dose mid-course.
2
Always take with food and water
Taking each tablet with a meal and a full glass of water substantially reduces nausea — the most common reason for early discontinuation. Doxycycline absorption is only minimally affected by food, unlike some other antibiotics.
3
Stay upright for 30 minutes
After each dose, remain sitting or standing for at least 30 minutes to ensure the tablet reaches the stomach before dissolving, protecting the oesophagus from irritation.
4
Use sun protection throughout
Apply SPF 30 or higher to exposed skin each morning while taking doxycycline and for 2–3 days after finishing the course. Photosensitivity can cause a painful sunburn-like reaction even from brief outdoor exposure.
5
Complete all 14 tablets
Even if symptoms have resolved by day 3 or 4, continue until the course is complete. Chlamydia’s intracellular life cycle means the bacteria may still be present even when symptoms abate.
After Treatment: What to Do
The same post-treatment steps apply whether you have taken doxycycline or azithromycin.
- Abstain from sex for 7 days after completing the full 7-day doxycycline course — i.e. 14 days from the start of treatment. Do not have any sexual contact, including oral sex, until 7 days have passed since your last tablet.
- Notify all recent sexual partners — all partners from the past 6 months should be informed, tested, and treated. See our partner notification guide.
- Retest at 3 months — BASHH recommends retesting 3 months post-treatment to detect reinfection. A routine test of cure is not required for non-pregnant patients on doxycycline, unless infection was rectal or pharyngeal.
- Return if symptoms persist — if symptoms do not resolve within 7 days of completing treatment, contact your prescriber. Consider whether a partner has been tested and treated.
First-line treatment (BASHH 2025)
Doxycycline 100 mg
100 mg twice daily for 7 days. Current BASHH first-line for urogenital and rectal chlamydia. Prescription following clinical assessment.
View doxycycline →Second-line / pregnancy alternative
Azithromycin 1 g
Single-dose alternative when doxycycline is contraindicated. Prescription following clinical assessment.
View azithromycin →Getting Doxycycline for Chlamydia Online in the UK
Doxycycline is a prescription-only medicine in the UK. A valid prescription from a registered prescriber is required — it cannot be purchased legally without one. GPhC-registered online pharmacies can conduct remote clinical assessments and issue prescriptions through pharmacist independent prescribers, allowing you to receive treatment without visiting a GP or sexual health clinic in person.
A legitimate online prescribing service will ask about your symptoms, sexual history, current medications, allergies, pregnancy status, and relevant medical history before issuing a prescription. Avoid any service that dispenses prescription antibiotics without conducting a clinical assessment.
Start Your Private Chlamydia Consultation
Access Doctor is a GPhC-registered pharmacy (#9011198). Our pharmacist independent prescribers will review your case, select the right antibiotic for your circumstances, and arrange same-day dispatch with discreet next-day delivery anywhere in the UK.
Start Consultation →Frequently Asked Questions about Doxycycline for Chlamydia
Why is doxycycline now recommended instead of azithromycin?
BASHH updated its chlamydia guidelines in 2025 following review of clinical trial data, including the REACT trial. The key driver was doxycycline’s superior cure rate for rectal chlamydia (near 100% vs approximately 83% for single-dose azithromycin). As rectal infection is increasingly identified through anatomical site testing, a first-line treatment effective at all sites became the clinical priority. For urogenital infection, cure rates with both drugs are similar, with doxycycline marginally higher.
Can I take doxycycline with the contraceptive pill?
Current evidence does not support a clinically significant interaction between doxycycline and combined hormonal contraceptives. You do not need to use additional contraception during a 7-day doxycycline course solely because of antibiotic use. However, if doxycycline causes vomiting within 2–3 hours of taking your pill, treat this as a missed pill and follow the instructions in your pill leaflet.
What happens if I miss a dose of doxycycline?
If you remember within a few hours of a missed dose, take it as soon as you remember. If it is close to the time of your next scheduled dose, skip the missed dose and continue as normal — do not double up. Complete the full 7-day course regardless. Contact your prescriber if you have missed multiple doses, as a 7-day course cut short may not reliably clear the infection.
Can I drink alcohol while taking doxycycline?
Alcohol does not directly interact with doxycycline in a dangerous way. However, heavy alcohol consumption can speed up doxycycline’s metabolism in the liver, potentially reducing drug levels below therapeutic concentrations. Alcohol also worsens nausea, the most common side effect. Moderate alcohol intake is unlikely to be harmful, but minimising it during the 7-day course is advisable.
Do I need a test of cure after doxycycline?
For non-pregnant patients with urogenital chlamydia who complete the full 7-day course, a routine test of cure is not recommended by BASHH. You should retest at 3 months to detect reinfection. Test of cure is recommended for rectal and pharyngeal infection, for chlamydia treated in pregnancy, and if symptoms persist after completing treatment.
How soon does doxycycline start working for chlamydia?
Doxycycline begins inhibiting chlamydial protein synthesis from the first dose. Symptom improvement is typically noticeable within 3–5 days. However, microbiological clearance requires completing the full 7-day course. Do not stop early because symptoms have improved — the infection may not be fully cleared. Abstain from sex for 7 days after the last tablet.
Is doxycycline safe in breastfeeding?
Doxycycline is excreted in breast milk. Short-term use (up to 3 weeks) for a nursing mother is generally considered low risk for the infant under specialist guidance, as the amount absorbed from breast milk is small. However, the standard advice is to discuss with your prescriber or pharmacist, who will weigh the clinical need against any potential risk and may suggest alternative antibiotics if available and appropriate.
References
- BASHH. UK National Guideline for the Management of Infection with Chlamydia trachomatis. Updated 2025. Available at: www.bashh.org/guidelines
- Manhart LE, et al. Randomised controlled trial comparing doxycycline and azithromycin for Chlamydia trachomatis treatment, including rectal infection (the REACT trial). Clin Infect Dis. 2021.
- 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.
- BNF. Doxycycline. British National Formulary. 2025. Available at: bnf.nice.org.uk
- Electronic Medicines Compendium (eMC). Doxycycline 100 mg capsules — Summary of Product Characteristics. Available at: www.medicines.org.uk/emc
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Doxycycline is a prescription-only medicine (POM). It must not be taken without a valid prescription issued following a clinical assessment. Always consult a qualified healthcare professional. Doxycycline is contraindicated in pregnancy. In a medical emergency, call 999.