What antibiotic clears chlamydia? Your guide to treatment options

October 12, 2025 •

4 min read

Chlamydia is the most commonly reported bacterial sexually transmitted infection in the United States, with a high prevalence among sexually active individuals under 25. An effective antibiotic clears chlamydia by targeting the Chlamydia trachomatis bacterium, though treatment strategies have evolved to address efficacy and adherence concerns.

Quick Summary

Chlamydia is a common sexually transmitted infection treated with antibiotics. Current guidelines prioritize a 7-day course of doxycycline over the single-dose azithromycin due to increased effectiveness, particularly for rectal infections.

Key Points

Doxycycline is the Preferred Treatment: For non-pregnant adults and adolescents, the CDC recommends a 7-day course of doxycycline (100 mg twice daily) as the primary treatment.
Azithromycin is a Secondary Option: A single 1-gram oral dose of azithromycin is a less-effective alternative, especially for rectal infections, and may require a test of cure.
Treatment Differs for Pregnant Individuals: Doxycycline is contraindicated in pregnancy; therefore, azithromycin (single 1g dose) is the recommended treatment.
Preventing Reinfection is Key: Abstinence from sexual activity is required for 7 days after a single-dose treatment or until a 7-day course is completed, and after all partners have been treated.
Partner Treatment is Essential: All sexual partners from the last 60 days must be evaluated, tested, and treated to prevent reinfection.
Retesting is Recommended: Due to high rates of reinfection, retesting at approximately 3 months after treatment is advised for both non-pregnant men and women.
Consideration for Rectal Infections: Because azithromycin has demonstrated lower efficacy for rectal infections, doxycycline is the preferred treatment for these cases.

Understanding Chlamydia and Its Treatment

Chlamydia is a bacterial infection caused by Chlamydia trachomatis that can affect the genitals, rectum, and throat. While many infections are asymptomatic, untreated chlamydia can lead to serious health issues, such as pelvic inflammatory disease, ectopic pregnancy, and infertility in women. For this reason, prompt and effective antibiotic treatment is crucial. The Centers for Disease Control and Prevention (CDC) issues guidelines to help healthcare providers manage and treat this common infection.

The Shifting Landscape of Antibiotics for Chlamydia

For many years, the single-dose regimen of azithromycin was a popular treatment for chlamydia due to its convenience and improved patient adherence. However, recent evidence, including clinical trials, has shown that azithromycin is less effective than doxycycline for certain infections. This has led to updated CDC guidelines that now recommend a different antibiotic as the preferred first-line therapy.

The CDC's Preferred Antibiotic: Doxycycline

The 2021 CDC guidelines recommend a 7-day course of doxycycline as the first-line treatment for uncomplicated chlamydial infections in non-pregnant adolescents and adults.

How Doxycycline Works

Doxycycline is a tetracycline antibiotic that inhibits bacterial protein synthesis, preventing the bacteria from growing and multiplying. It is highly effective against chlamydia at various sites of infection.

Dosing: 100 mg taken orally twice a day for 7 days.
Effectiveness: High cure rates for infections in the urethra, cervix, rectum, and pharynx.
Compliance: Requires completing the full 7-day course for effectiveness.

The Alternative Antibiotic: Azithromycin

Azithromycin is an alternative treatment option for chlamydia, though no longer the first-line choice for non-pregnant patients.

When Azithromycin is Used

Azithromycin is a macrolide antibiotic that also inhibits bacterial protein synthesis. The single-dose regimen can be useful when patient adherence to a longer course is a concern.

Dosing: A single 1-gram oral dose.
Limitations: It is less effective than doxycycline for treating rectal infections, and follow-up testing may be needed if used for this purpose.

Comparison of Antibiotic Treatments


Feature	Doxycycline	Azithromycin	Special Population (Pregnancy)
CDC Recommendation	First-line regimen for adolescents and adults.	Alternative regimen for non-pregnant adolescents and adults.	Preferred regimen: Azithromycin 1 g orally in a single dose.
Dosing Schedule	100 mg orally twice a day for 7 days.	1 g orally in a single dose.	1 g orally in a single dose.
Effectiveness	High effectiveness for urogenital, rectal, and pharyngeal infections.	High for urogenital, but lower effectiveness for rectal infections.	Safe and effective during pregnancy.
Adherence	Requires patient compliance over 7 days.	High adherence due to single dose.	High adherence due to single dose.
Test of Cure	Not typically required unless reinfection is suspected.	Recommended for rectal infections due to lower efficacy.	Recommended approximately 4 weeks after therapy to confirm eradication.
Contraindications	Contraindicated in the second and third trimesters of pregnancy and in young children due to risk of tooth discoloration.	Limited data for infants <6 weeks due to potential link to infantile hypertrophic pyloric stenosis.	Doxycycline contraindicated.

Treatment Considerations for Specific Populations

Pregnant Patients

Doxycycline is contraindicated during pregnancy due to the risk of tooth discoloration in the fetus. The recommended treatment is a single 1-gram oral dose of azithromycin, with amoxicillin as an alternative. A test of cure is important for pregnant patients.

Infants and Children

Specific regimens like erythromycin are used for chlamydial conjunctivitis or pneumonia in infants. Amoxicillin and erythromycin are alternatives for pregnant women. Erythromycin is used for infants, but a second course might be needed due to lower efficacy.

Beyond the Antibiotic: Addressing Treatment Challenges

Successful treatment depends on several factors. Treatment failure or repeat infections can occur due to:

Reinfection from Untreated Partners: The most common cause of repeat infection is unprotected sex with an untreated partner. Partner therapy can help prevent this.
Poor Adherence: Not completing the full antibiotic course can lead to treatment failure.
Persistent Infection: While rare in clinical settings, C. trachomatis may enter an antibiotic-resistant state under certain conditions.
Incorrect Diagnosis: A positive test after treatment might be due to non-viable bacterial DNA rather than active infection, especially if tested too soon.

Prevention and Follow-Up Are Key

To ensure a successful cure and prevent complications, it is essential to follow post-treatment guidelines. Treating all sexual partners simultaneously prevents reinfection.

Abstain from Sex: Avoid sexual intercourse for 7 days after single-dose treatment or until completing a 7-day regimen and symptoms resolve.
Retesting is Recommended: Retesting for chlamydia is recommended about 3 months after treatment for both men and women to check for reinfection.

Conclusion

Chlamydia is curable with appropriate antibiotics. The CDC now recommends a 7-day course of doxycycline as the first-line treatment for most cases, particularly for its effectiveness against rectal infections. Azithromycin remains an alternative, especially for pregnant patients or when adherence is a concern. Successful treatment requires taking medication as prescribed, ensuring partners are treated, and preventing reinfection. Consult a healthcare provider for diagnosis and treatment based on current guidelines.

Learn more about chlamydia and other STIs from the official CDC website.

Frequently Asked Questions

According to the latest Centers for Disease Control and Prevention (CDC) guidelines, doxycycline (100 mg twice daily for 7 days) is the first-line and preferred antibiotic for treating uncomplicated chlamydia in non-pregnant patients.

Recent studies have shown that azithromycin is significantly less effective than doxycycline for clearing rectal chlamydia infections. Since rectal infections often go undetected, doxycycline provides more consistent effectiveness across all potential sites of infection.

Yes, a single 1-gram oral dose of azithromycin is still an alternative option, particularly in cases where adherence to a longer regimen of doxycycline is a concern. However, it is less effective for rectal infections and may require a follow-up test.

For pregnant women, the recommended treatment is a single 1-gram oral dose of azithromycin. Doxycycline is contraindicated because it can cause permanent tooth discoloration in the fetus.

Symptoms typically begin to resolve within a few days to a week after starting antibiotics. However, it is crucial to complete the entire course of medication, even if you start feeling better, to ensure the infection is completely cleared.

The most effective way to avoid reinfection is to ensure that all recent sexual partners are also tested and treated. Abstain from sexual contact until 7 days after both you and your partner have completed treatment.

Yes, the CDC recommends that all non-pregnant patients retest for chlamydia approximately 3 months after treatment to check for reinfection. A test of cure is specifically recommended for pregnant patients and those treated with azithromycin for rectal infections.