Which Antibiotics Treat Which STDs? A No-Judgment Guide

Published: October 2025 | Last updated: May 2026

When something feels off after sex, the first instinct for many people is to find a fix without a phone call, a waiting room, or an ID at a clinic. The search history fills up: "antibiotics for chlamydia at home", "what antibiotic treats gonorrhea", "is doxycycline for STDs". The questions feel urgent, and the answers are rarely what people are hoping for.

Here is the short version, before the rest of this article gets into the detail. Antibiotics work on bacterial sexually transmitted infections, which means chlamydia, gonorrhea, syphilis, trichomoniasis, and Mycoplasma genitalium. They do nothing against viral infections like herpes, HPV, hepatitis B, or HIV. Even within the bacterial group, the right drug, dose, and route depend on the specific infection, where it lives in the body, and whether anyone has been treating it incorrectly already. There is no single antibiotic that covers everything, and there is no safe shortcut around getting a real test result before swallowing pills.

This guide walks through which antibiotics the CDC currently recommends for which infections, how long the pills typically take to work, why some treatments fail, where antibiotic-resistant gonorrhea fits in, and what to do if symptoms keep coming back after a course of medication. No shame, no scare tactics, just current public-health guidance translated into plain English.

What Symptoms Send People Searching for STD Antibiotics?

The search for STD antibiotics rarely starts with a confirmed diagnosis. It usually starts with a symptom that feels too embarrassing to bring up casually: a sting when peeing, a bump that does not look like an ingrown hair, discharge that has changed color or smell, or a sore that is taking too long to disappear.

The problem is that none of those symptoms map cleanly onto a single infection. Burning during urination can come from gonorrhea, but it can also come from a urinary tract infection, trichomoniasis, prostatitis, or simple irritation from a new soap or condom material. Discharge is associated with chlamydia and gonorrhea but also with bacterial vaginosis, yeast overgrowth, and trichomoniasis. A sore throat that lingers for weeks could be pharyngeal gonorrhea, but it is far more likely to be a viral pharyngitis that resolves on its own.

This overlap is why guessing at the answer and reaching for a leftover pill bottle is one of the most common ways treatment goes sideways. Pick the wrong antibiotic and the underlying infection keeps growing while symptoms quiet down enough to feel reassuring. Pick the right one but at the wrong dose and the bacteria gets a partial knock instead of a full one, which is precisely how resistant strains get a foothold. For chlamydia in particular, a half-treated infection can climb the upper reproductive tract and cause pelvic inflammatory disease, with longer-term consequences for fertility and chronic pelvic pain.

A real diagnosis, whether through an at-home rapid test panel, a clinic swab, or a lab-processed urine NAAT (nucleic acid amplification test), is the only way to match an antibiotic to the actual organism.

Which Antibiotics Treat Which STDs? Current CDC Guidance

The CDC's STI Treatment Guidelines, last fully updated in 2021 and refreshed periodically since, lay out a specific drug, dose, and duration for each bacterial STI. These are the regimens clinicians are working from when they prescribe.

Chlamydia. The first-line treatment is doxycycline 100mg taken twice daily for seven days. Until 2021, single-dose azithromycin (1g) was the more common prescription, but the updated CDC guidance moved doxycycline to first-line because of better cure rates, particularly for rectal infections. Azithromycin remains an alternative when doxycycline is not tolerated, and amoxicillin is the preferred option in pregnancy.

Gonorrhea. The first-line regimen is a single 500mg intramuscular injection of ceftriaxone (1g if the patient weighs more than 150kg). Oral cephalosporins are no longer recommended as first-line because of declining effectiveness, and the routine addition of azithromycin was dropped unless chlamydia coinfection has not been ruled out. The shift to a single, larger ceftriaxone dose is itself a response to creeping resistance.

Syphilis. For primary, secondary, and early latent syphilis, a single intramuscular dose of benzathine penicillin G (2.4 million units, per the CDC's per-stage syphilis guidance) is the standard. Late latent syphilis requires three weekly doses; neurosyphilis requires intravenous penicillin in a hospital setting. There is no oral substitute that the CDC considers equivalent. Doxycycline is reserved for non-pregnant patients with documented penicillin allergies.

Trichomoniasis. The CDC's 2021 update changed first-line treatment for women from a single 2g dose of metronidazole to a multi-day course (500mg twice daily for seven days), based on better clearance rates in clinical trials. For men, a single 2g dose of metronidazole or tinidazole remains acceptable. The UK's NHS gives the same metronidazole guidance and stresses that recent partners need treating at the same time to stop the infection bouncing back and forth (NHS, trichomoniasis).

Mycoplasma genitalium. This is the trickier bacterial STI. It carries widespread resistance to the macrolide and tetracycline drugs that work on most other organisms, which is why the CDC recommends a two-step protocol: doxycycline 100mg twice daily for seven days to lower the bacterial load, followed by azithromycin (a multi-day course) if resistance testing shows a macrolide-sensitive strain, or moxifloxacin (seven-day course) if the strain is macrolide-resistant. Where resistance testing is not available, providers often default to the moxifloxacin sequence.

When the Pills Do Not Work: Why Treatment Fails

Treatment failure is more common than people expect, and it is usually not a sign that someone did anything wrong. The most frequent reasons a course of antibiotics does not clear an infection are: the wrong drug was prescribed for what turned out to be a different organism, the dose or duration was too short, treatment started so early after exposure that the infection had not fully established, the partner was not treated and reinfection happened the moment unprotected sex resumed, or the strain itself has reduced susceptibility to the prescribed drug.

That last one is becoming a louder concern, particularly for gonorrhea. The CDC has flagged drug-resistant Neisseria gonorrhoeae as one of the urgent antimicrobial-resistance threats in the United States, with treatment options narrowing over the past two decades. Gonorrhea's resistance story is not new: fluoroquinolones such as ciprofloxacin were dropped from gonorrhea treatment back in 2007 after the organism outpaced them, and the World Health Organization now reports high global resistance to quinolones, azithromycin, and even the extended-spectrum cephalosporins that represent the last-line option (WHO STIs fact sheet). The reason ceftriaxone is now given at 500mg instead of the older 250mg dose is exactly this: the previous dose was no longer producing reliable cure rates against newer strains.

Absorption matters too. Tetracycline-class antibiotics like doxycycline bind to calcium, magnesium, iron, and aluminum, which is why providers tell patients to take it without dairy, antacids, or iron supplements within two hours of the dose. A pill swallowed with a coffee splash of milk performs worse than one swallowed with plain water.

Clinicians sometimes describe a familiar pattern: a patient prescribed empirically for chlamydia whose symptoms ease briefly, then return because there was an undetected gonorrhea coinfection that azithromycin alone did not fully cover. The fix is not more of the same drug; it is retesting, identifying the actual organism, and switching to a regimen that covers it.

Gonorrhea has progressively developed resistance to the antibiotic drugs prescribed to treat it. The emergence of cephalosporin resistance would significantly complicate the ability of providers to treat gonorrhea successfully.

How Long Should Antibiotics Take to Work?

Antibiotics clear the bacteria faster than the body resolves the resulting inflammation, which is why patients often feel meaningfully better within days while the laboratory test that confirms cure still takes weeks. "I feel better, so I must be cured" is one of the more dangerous assumptions in STI treatment, because the inflammation cools well before the lab work catches up.

The general pattern: gonorrhea symptoms (urethral discharge, burning on urination) usually start easing within one to three days after the ceftriaxone injection. Chlamydia symptoms typically improve within two to five days of starting doxycycline, though the full seven-day course is required to clear the infection. Syphilis lesions begin healing within three to seven days of the penicillin injection, but blood-test confirmation of treatment success takes months, with follow-up titers at six and twelve months. Trichomoniasis usually clears symptomatically within a few days of starting metronidazole. Mycoplasma genitalium can take a week or more, partly because the two-step protocol stretches the active treatment period across two consecutive antibiotic courses.

If symptoms are dramatically worse rather than better at 48 to 72 hours, or if new symptoms appear (severe abdominal pain, fever, swollen testicles, heavy vaginal bleeding), that is a reason to be seen urgently. It can indicate a worsening or complicated infection that needs a different intervention.

Wait, Was It Even an STD in the First Place?

A meaningful share of people who get treated for an STI turn out to have something else. Bacterial vaginosis, yeast overgrowth, urinary tract infections, prostatitis, contact dermatitis from new products, and irritation from latex or spermicide can all mimic the symptoms that drive someone to ask for antibiotics in the first place. Non-specific urethritis, where there is genuine inflammation but no identifiable STI organism, is another common diagnosis when the swab comes back negative but symptoms persist.

This is more than a clinical curiosity. Treating a yeast infection with antibiotics will usually make it worse by killing off the protective bacteria the body relies on to keep yeast in check. Treating bacterial vaginosis as if it were chlamydia means the actual cause keeps recurring while the patient assumes they have an antibiotic-resistant STI. Treating chronic bacterial prostatitis with a single dose of azithromycin is unlikely to clear it; it often needs four to six weeks of a fluoroquinolone (such as ciprofloxacin) or trimethoprim-sulfamethoxazole.

If a course of antibiotics did not resolve the symptom, asking what was actually being treated is more useful than asking for a stronger version of the same drug. The table below sketches the categories so the conversation with a clinician (or the order on a home test panel) can be more specific.

Re-Infection: When You Got Better and Your Partner Did Not

A common pattern is treatment that worked the first time, followed by symptoms that come back a few weeks later. The bacteria did not develop resistance overnight; the patient was reinfected by an untreated partner. STI treatment does not build lasting immunity, which is why the same organism can return as soon as the protective barrier of antibiotics fades.

Expedited partner therapy, where a clinician prescribes treatment for a partner without an in-person visit, is allowed in most U.S. states for chlamydia and gonorrhea. It is not allowed in every state, and not every clinic offers it where it is permitted. In practice, the burden of telling a partner often falls to the patient, and the partner has to navigate getting tested and treated independently.

Until both partners have completed treatment and waited the full abstinence window (typically seven days after the last dose, or seven days after both partners have finished, whichever is longer), unprotected sex risks ping-ponging the infection back and forth. This is one of the more common ways "resistant" infections get a head start. The bacteria did not mutate dramatically overnight; partial treatment plus repeated exposure gave the strain multiple opportunities to adapt.

Breaking the cycle requires three things in combination: confirm your own treatment is complete, confirm every recent partner has been treated, and use protection for the recommended window even after both sides have finished medication.

Disclosure: this site sells rapid at-home STI test kits; the panels referenced below are our products.

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Why Antibiotics Do Not Work on Viral STIs

Antibiotics are designed to kill or stop the growth of bacteria, so they do nothing against viruses. That is why a course of doxycycline has no effect on herpes, HPV, hepatitis B, or HIV. The mechanism mismatch is total: bacteria have cell walls and metabolic machinery the drugs target, and viruses do not. Public-health resources put the rule plainly, that antibiotics treat bacterial and parasitic STIs while viral ones are managed with antiviral medicines.

Herpes simplex (HSV-1 and HSV-2) is managed with antivirals such as acyclovir, valacyclovir, or famciclovir. These shorten outbreaks and, when taken as daily suppressive therapy, reduce the chance of transmitting the virus to a partner. They do not eliminate it; HSV stays in nerve cells for life and can reactivate. That sounds bleak written out, but most people with HSV-2 have outbreaks that become less frequent and less severe over time, and many people with HSV-1 (the strain most often associated with cold sores but increasingly responsible for genital herpes too) never develop noticeable symptoms. In practical terms, managing HSV-2 might mean a daily 500mg valacyclovir tablet and the awareness that suppressive therapy substantially lowers transmission risk to a partner.

HPV usually clears on its own within one to two years thanks to immune response, though some high-risk strains can persist and cause cervical or other cancers if not detected early. There is no antiviral that treats HPV directly; treatment is aimed at the consequences (genital warts, abnormal cervical cells), not the virus. The HPV vaccine prevents most cancer-causing strains and is recommended routinely through age 26, with shared clinical decision-making for adults aged 27 to 45.

HIV is now a chronic, manageable condition for most people who can access daily antiretroviral therapy. Modern regimens can suppress the virus to undetectable levels in the bloodstream, which means it cannot be transmitted sexually, the basis for the U=U (Undetectable equals Untransmittable) public-health message endorsed by the CDC.

Hepatitis B has both a preventive vaccine and treatments to suppress chronic infection (typically tenofovir or entecavir). Hepatitis C, despite being viral, is now considered curable in most patients with eight to twelve weeks of direct-acting antivirals like sofosbuvir/velpatasvir. None of these treatments are antibiotics.

Cure, Control, or Confusion: What "Treatment" Really Means

Clinicians use the word "cure" carefully. With STIs, that word applies to most bacterial infections caught and treated correctly. Chlamydia and gonorrhea, treated with the right regimen and confirmed by retest, are gone. Syphilis, treated early enough, is gone. Trichomoniasis, treated with the multi-day metronidazole regimen, clears at significantly higher rates than the older single-dose approach; the 2021 CDC update was driven by trial data showing roughly half as many positive retests at one month. Mycoplasma genitalium can be cured but is the most likely of the bacterial STIs to relapse, which is why a test of cure a few weeks out matters.

For viral infections, the word "cure" mostly does not apply. Hepatitis C is the standout exception: direct-acting antivirals genuinely eliminate the virus from the body for most patients. For HIV, herpes, and HPV, the relevant words are "control" or "manage." That distinction matters because it changes what success looks like. A herpes diagnosis is not a one-time event with a finite endpoint; it is a condition that is present in the background, sometimes flares up, and is managed with medication and partner conversations.

What to Do If Antibiotics Did Not Clear Your Symptoms

If a course of antibiotics did not fully clear your symptoms, the least useful next move is another round of the same pills on a hunch. A short, structured check tells you more: it sorts a missed coinfection from a reinfection from something that was never an STI in the first place.

A multi-infection home panel is useful for that first "is this still the same thing" check before you decide whether a follow-up clinic visit makes sense; it tells you more than retesting a single organism. Home rapid panels are no replacement for clinical care, and a positive result warrants a provider conversation rather than another round of self-treatment. Work through the questions below first.

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1. U.S. Centers for Disease Control and Prevention. Sexually Transmitted Infections Treatment Guidelines, main page. Source for general STI treatment recommendations, retest intervals, and partner-treatment guidance across all infections discussed in this article.
2. U.S. Centers for Disease Control and Prevention. Chlamydial Infections, STI Treatment Guidelines. Source for the doxycycline 100mg twice daily for seven days first-line regimen.
3. U.S. Centers for Disease Control and Prevention. Gonococcal Infections Among Adolescents and Adults, STI Treatment Guidelines. Source for the 500mg intramuscular ceftriaxone single-dose regimen and the discontinuation of routine dual therapy.
4. U.S. Centers for Disease Control and Prevention. Syphilis, STI Treatment Guidelines. Source for benzathine penicillin G as the preferred drug across early and late stages of disease; the per-stage 2.4 million unit dosing appears on the linked per-stage sub-guidelines.
5. U.S. Centers for Disease Control and Prevention. Trichomoniasis, STI Treatment Guidelines. Source for the 2021 update changing first-line treatment for women to multi-day metronidazole (500mg twice daily for seven days) and the roughly halved 1-month positive-retest rate.
6. U.S. Centers for Disease Control and Prevention. Mycoplasma genitalium, STI Treatment Guidelines. Source for the two-step doxycycline-then-moxifloxacin (or azithromycin) protocol and resistance-testing recommendation.
7. U.S. Centers for Disease Control and Prevention. Antimicrobial Resistance Threats. Lists Drug-Resistant Neisseria gonorrhoeae as an Urgent Threat in the United States.
8. World Health Organization. Sexually transmitted infections (STIs) fact sheet. Source for the four curable bacterial STIs and the global rise of antibiotic resistance in gonorrhea, including resistance to quinolones, azithromycin, and extended-spectrum cephalosporins.
9. UK National Health Service. Trichomoniasis. Source confirming metronidazole treatment (twice daily for seven days, or a single dose) and the need to treat recent partners at the same time.
10. MedlinePlus (U.S. National Library of Medicine). Sexually Transmitted Infections. Source for the core principle that antibiotics treat bacterial and parasitic STIs while viral STIs are managed with antiviral medicines rather than cured.

Sam Harper

Sam covers at-home sexual-health testing, public-health guidance, and clinical-testing basics for general audiences. Has been writing about consumer health since 2019, with a focus on translating CDC and WHO guidance into plain-English action items. Not a clinician; articles are summaries, not advice.