A sexually transmitted infection (STI) is an infection a person may acquire through sexual contact. Treatments are available, particularly in the early stages. For some STIs, antibiotics such as azithromycin are an effective option for clearing the infection.

STIs are infections that typically pass from one person to another through sexual contact. Anyone, regardless of their sexual orientation or hygiene standards, can contract these infections. Many types of bacteria can cause STIs. To treat these infections, a doctor will typically prescribe antibiotics.

Azithromycin is an antibiotic a doctor may recommend for some STIs. For example, it is a common treatment option for chlamydia and for potential complications from chlamydia, such as nongonococcal urethritis, cervicitis, or lymphogranuloma venereum.

In this article, we will discuss azithromycin, including whether it treats STIs and how to use it.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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According to the Centers for Disease Control and Prevention (CDC), azithromycin is the recommended treatment for chlamydia, nongonococcal urethritis, and cervicitis. Additionally, health experts may recommend azithromycin as part of dual therapy alongside gentamicin to treat gonorrhea if a person is allergic to ceftriaxone.

The results of a 2015 study comparing different antibiotics for treating chlamydia suggest that azithromycin can treat 97% of cases. However, the study indicates that another antibiotic, doxycycline, may be more effective for treating chlamydia.

Other studies also suggest that doxycycline may be more effective for treating chlamydia in both males and females.

Still, the British Association for Sexual Health and HIV states that azithromycin should remain an option for individuals who are allergic or intolerant to tetracyclines, such as doxycycline, and for people who are pregnant.

Additionally, the CDC Sexually Transmitted Infections Treatment Guidelines suggest that azithromycin may be effective for other STIs, such as:

Azithromycin is available in both tablet and powder formulations. The dosage will vary depending on the infection a person is treating. A doctor will advise on the dosage and duration of medication.

For treatment of chlamydia, a doctor will likely recommend that a person take 1 gram (g) of azithromycin orally in a single dose. If a person is using azithromycin for the dual treatment of gonorrhea, a single dose of 2 g orally is advisable. A person should also then receive 240 milligrams (mg) of gentamicin in a single intramuscular injection.

For the treatment of nongonococcal urethritis, a doctor will suggest a single dose of 1 g of oral azithromycin. Alternatively, they may advise taking 500 mg orally in a single dose followed by 250 mg orally per day for 4 days. If a person is treating cervicitis with azithromycin, the dosage recommendation is 1 g orally in a single dose.

Like any other medication, azithromycin can cause side effects. It is advisable to consult a doctor if any of the following adverse reactions are severe or do not go away:

  • diarrhea
  • nausea
  • vomiting
  • stomach pain
  • headache

Occasionally, a person may experience more serious side effects, which can include:

  • fast, pounding, or irregular heartbeat
  • dizziness
  • fainting
  • rash with or without a fever
  • blisters or peeling
  • fever and pus-filled, blister-like sores, redness, and swelling of the skin
  • hives
  • itching
  • wheezing or difficulty breathing or swallowing
  • swelling of the face, throat, tongue, lips, eyes, hands, feet, ankles, or lower legs
  • hoarseness

If a person is sexually active, it is highly advisable that they regularly test for STIs to protect their health. A person can talk with their usual healthcare professional about STI testing, or they may feel more comfortable going to a confidential testing clinic.

STI testing recommendations include:

  • Adults and adolescents aged 13–64: It is advisable for a person to test at least once for HIV.
  • Sexually active females: It is advisable that females younger than age 25 test for gonorrhea and chlamydia every year. Females who are over age 25 and have risk factors — such as new or multiple sexual partners or a sexual partner who already has an STI — should test for gonorrhea and chlamydia every year.
  • A person who is pregnant: A pregnant individual may want to consider testing for syphilis, HIV, hepatitis B, hepatitis C, chlamydia, and gonorrhea starting in early pregnancy.
  • Sexually active males who have sex with males: It is advisable for a person to:
    • test at least once a year for syphilis, chlamydia, and gonorrhea
    • test at least once a year for HIV
    • test at least once a year for hepatitis C if living with HIV
    • consider testing more frequently (e.g., every 3–6 months) if they have multiple or anonymous partners
  • Sexually active males who have sex with females: There is not enough evidence for screening among males who have sex with females and are at low risk. However, a person may wish to test once they become sexually active.
  • Transgender and gender diverse persons: It is advisable that a person follow screening recommendations based on their anatomy. A person may want to consider annual testing, depending on their risk factors.
  • An individual who has had oral or anal sex: A person may want consult a healthcare professional about throat and rectal testing options.

Learn more about STI testing.

Below we answer some frequently asked questions about the use of azithromycin and STIs.

How quickly does azithromycin work?

Azithromycin can take approximately 1 week to treat an STI. It may take up to 2 weeks to effectively clear the infection. A person may start to feel better within 2–3 days.

To prevent passing the infection to others, it is advisable for a person to avoid sexual contact until the infection completely clears.

What happens if a person does not treat STIs?

If a person has an STI and does not receive treatment, their symptoms may worsen and become more severe.

For example, untreated chlamydia may result in pelvic inflammatory disease in females, which may lead to infertility and long-term abdominal pain. In males, it can cause testicular pain and infertility.

Untreated STIs can also lead to problems during pregnancy, and it is possible for a pregnant person’s baby to contract the infections during delivery.

How to prevent STIs

There are several ways a person can prevent or decrease the risk of contracting an STI, including:

  • Pre-exposure vaccination: Vaccinations can prevent transmission of some STIs. For example, healthcare professionals routinely recommend the HPV vaccine for males and females aged 11 or 12.
  • Condoms: When people use them correctly, both internal and external condoms can reduce the risk of acquiring or transmitting STIs.
  • Abstinence and reduction in number of sexual partners: A person can prevent STI transmission either by abstaining from sexual activities or by engaging in sexual contact only with a monogamous partner who does not have any STIs.

Azithromycin is an antibiotic a doctor may prescribe to treat STIs that result from bacteria. It is a common and effective treatment option for chlamydia.

Untreated STIs can lead to further health complications. As such, it is advisable for sexually active individuals to take measures to reduce the likelihood of contracting an STI, such as safer sex practices and regular screenings.