The antibiotics used to treat STDs depend entirely on which infection you have. Chlamydia, gonorrhea, syphilis, and trichomoniasis each require different drugs, different formats (pills versus injections), and different treatment lengths. Some clear up with a single dose, while others need a week or more of daily medication. Here’s what’s currently recommended for each major bacterial and parasitic STD.
Chlamydia
Chlamydia is treated with doxycycline, taken twice a day for seven days. This is the current first-line recommendation from the CDC, replacing the old single-dose azithromycin approach that was standard for years. Azithromycin (a one-time oral dose) is still an option if doxycycline isn’t suitable, but doxycycline has proven more effective.
The seven-day course means you need to finish all your pills even if symptoms disappear early. Pregnant women treated for chlamydia are typically retested four weeks after treatment to confirm the infection has cleared, and again within three months. Retesting is recommended for anyone treated for chlamydia, since reinfection is common.
Gonorrhea
Gonorrhea requires an injection. The standard treatment is a single shot of ceftriaxone, a powerful antibiotic delivered into the muscle. You can’t treat gonorrhea with pills alone in most cases. If you have a cephalosporin allergy that rules out ceftriaxone, a combination of two other drugs (gentamicin injection plus oral azithromycin) is an alternative for genital or rectal infections.
An oral option, cefixime, exists when an injection simply isn’t available, but it’s considered a backup rather than the preferred choice. For gonorrhea in the throat, there is no reliable alternative to the ceftriaxone injection.
Antibiotic resistance is a growing concern with gonorrhea. Between 2022 and 2024, resistance to ceftriaxone jumped from 0.8% to 5% globally, and resistance to cefixime rose from 1.7% to 11%, according to WHO surveillance data. Resistance to ciprofloxacin, an older antibiotic once commonly used for gonorrhea, has reached 95%, which is why it’s no longer recommended. This shifting resistance landscape is why gonorrhea treatment guidelines change more frequently than those for other STDs.
Syphilis
Syphilis is one of the few STDs still best treated with penicillin, specifically a long-acting injectable form called benzathine penicillin G. For primary and secondary syphilis (the earlier stages), a single injection is all that’s needed. If syphilis has progressed to a later stage or if the timing of infection is unclear, the treatment extends to three weekly injections.
Penicillin is so effective against syphilis that no other antibiotic fully replaces it, particularly for pregnant patients or people with neurosyphilis (infection that has reached the nervous system). If you have a documented penicillin allergy, your provider will likely explore whether desensitization is possible, especially in pregnancy, since alternatives are limited and less well studied for this infection.
Trichomoniasis
Trichomoniasis isn’t caused by bacteria but by a parasite, so it requires a different class of drug. Metronidazole is the standard treatment, but the recommended regimen differs by sex. Women are treated with metronidazole twice daily for seven days, while men receive a single larger dose all at once. The reason for this difference is that the longer course has been shown to be more effective at clearing the infection in women.
Tinidazole, a related drug, is an alternative for both men and women and is given as a single oral dose. Both metronidazole and tinidazole interact badly with alcohol. Drinking while taking either one (or within a couple of days after finishing) can cause severe nausea and vomiting.
Mycoplasma Genitalium
Mycoplasma genitalium is a lesser-known STD that causes symptoms similar to chlamydia, including burning during urination and unusual discharge. It’s harder to treat than most other STDs because it’s developed significant resistance to common antibiotics.
Treatment uses a two-stage approach. The first stage is a week of doxycycline to reduce the bacterial load. The second stage depends on resistance testing: if the infection is sensitive to macrolide antibiotics, a multi-day course of azithromycin follows. If it’s resistant, moxifloxacin is used instead. When resistance testing isn’t available, the default second stage is moxifloxacin, since it covers resistant strains. This resistance-guided approach achieves cure rates above 90%.
Pelvic Inflammatory Disease
When STDs like chlamydia or gonorrhea spread deeper into the reproductive tract, they can cause pelvic inflammatory disease (PID). Because PID often involves multiple types of bacteria at once, it requires combination antibiotic therapy rather than a single drug.
Outpatient treatment for PID involves a ceftriaxone injection plus two weeks of oral doxycycline and metronidazole. That’s notably longer and more complex than treating the underlying STD alone, which is one reason early detection matters. Severe cases may need IV antibiotics in a hospital setting.
Why Your Partner Needs Treatment Too
Antibiotics only work if both you and your sexual partner are treated. Otherwise, reinfection happens almost immediately. For chlamydia and gonorrhea, a practice called Expedited Partner Therapy allows your provider to write a prescription for your partner without examining them directly. You pick up the medication and deliver it yourself. This approach is especially useful when a partner can’t easily get to a clinic.
EPT is legal in most U.S. states for chlamydia and gonorrhea. It isn’t used for syphilis or other STDs that require injections or more complex follow-up.
What Antibiotics Cannot Treat
Not all STDs respond to antibiotics. Herpes, HIV, and hepatitis B are caused by viruses, not bacteria, so antibiotics have no effect on them. These infections are managed with antiviral medications that suppress the virus but don’t eliminate it. HPV (human papillomavirus) has no direct treatment at all; the immune system clears most HPV infections on its own, though the virus can cause lasting problems like genital warts or cervical cell changes that need separate management.
If you’re unsure which STD you have, testing is the essential first step. The right antibiotic depends entirely on the right diagnosis, and many STDs share overlapping symptoms or cause no symptoms at all.