Doxy-PEP: what it is, who it's for and how to get it

Doxy-PEP means taking a dose of doxycycline, a common antibiotic, within 72 hours after sex to lower the chance of getting syphilis, chlamydia and gonorrhea. CDC recommends that clinicians offer it to gay, bisexual and other men who have sex with men and to transgender women who had one of those infections in the past 12 months. It doesn't prevent HIV, so it doesn't replace PrEP. People who use it should get STI tests every 3 to 6 months. The cheapest common 4 panel we track, which tests for chlamydia, gonorrhea, syphilis and HIV, costs $119 (verified Nov 2, 2026) at Everlywell.

Key points

• In three large trials, CDC says, doxy-PEP cut syphilis and chlamydia infections by more than 70% and gonorrhea by about 50%.
• CDC's recommendation covers gay, bisexual and other men who have sex with men and transgender women with a bacterial STI in the past 12 months. For other groups, CDC says the evidence is too limited to recommend it.
• It doesn't prevent HIV or herpes.
• CDC recommends STI tests at each body site you use for sex before you start and every 3 to 6 months after.
• You need a prescription from a clinician, a sexual health clinic or a telehealth service.

What is doxy-PEP?

Doxycycline, "doxy" for short, is an antibiotic doctors use for infections such as chlamydia. PEP means post-exposure prophylaxis, medicine taken after a possible exposure to prevent an infection. Doxy-PEP is the same drug used a different way, as a single dose after sex instead of a course of treatment.

CDC's 2024 guidelines rest on three large randomized trials among men who have sex with men and transgender women. In them, CDC says, 200 mg of doxycycline taken within 72 hours after sex reduced syphilis and chlamydia infections by more than 70% and gonorrhea by about 50%. The one trial among cisgender women, in Kenya, found no significant reduction. Doxycycline turned up in the hair of only 29% of the women assigned to take it, so CDC's guideline says missed doses may explain the result, though biological differences still need study.

What doxy-PEP doesn't do

• It doesn't prevent HIV or herpes, CDC says. For HIV, the options are PrEP before an exposure and PEP after one.
• The doxy-PEP dose isn't strong enough to treat an STI you already have, CDC says. If a test is positive, your clinician prescribes treatment.

Who CDC recommends doxy-PEP for

CDC recommends that clinicians talk with gay, bisexual and other men who have sex with men and transgender women who had syphilis, chlamydia or gonorrhea in the past 12 months about the benefits and harms of doxy-PEP, and offer a prescription if they decide on it together. Clinicians could also discuss it with people in those groups who haven't had an STI in the past year but will be having sex that makes exposure more likely, CDC says.

For cisgender women, cisgender heterosexual men, transgender men and other queer and nonbinary people assigned female at birth, CDC says there isn't enough evidence to recommend it either way. Clinicians can use their judgment with people outside the recommendation.

Doxy-PEP vs PrEP and PEP

They prevent different infections, and many people use more than one. CDC's guidelines say doxy-PEP should come with HIV prevention, including PrEP for people who could benefit.

Our PrEP guide covers how to get PrEP and the HIV tests it needs.

How to take doxy-PEP

A clinician decides whether doxy-PEP suits you and how many pills make up one dose. CDC's guideline asks clinicians to prescribe "200 mg of doxycycline (any formulation) to be taken as soon as possible within 72 hours after having oral, vaginal, or anal sex with a maximum dose of 200 mg every 24 hours." The prescription should cover enough doses until your next visit, and CDC says not to share it.

CDC's tips to lower the chance of side effects:

• Take it with food and at least 8 ounces of water, and don't lie down for an hour afterward.
• Keep 2 hours between a dose and dairy products, antacids, or supplements with iron, calcium or magnesium.
• Wear sunscreen or cover up, because doxycycline can make your skin more sensitive to the sun.

CDC also suggests telling your clinician about every other medicine you take, including over-the-counter ones, so they can check for interactions.

Side effects and antibiotic resistance

CDC says most people can take doxycycline without significant side effects. Those it lists are nausea, upset stomach, diarrhea, sensitivity to the sun and irritation of the esophagus. In the IPERGAY trial, 53% of people taking doxy-PEP reported stomach or bowel side effects, compared with 41% of those who weren't, CDC's guideline reports.

Resistance is the larger open question. CDC says researchers are still learning whether doxy-PEP harms the helpful bacteria in the gut and on the skin, and whether it makes doxycycline work less well against common germs. In the DoxyPEP trial, CDC's guideline says, the share of people in the doxy-PEP group carrying tetracycline-resistant Staphylococcus aureus rose from 5% to 13% over a year, while the share carrying S. aureus at all fell from 44% to 31%. To limit resistance, CDC focuses its recommendation on the groups in which doxy-PEP has been shown to work.

STI testing while you use doxy-PEP

CDC says people prescribed doxy-PEP should be tested for bacterial STIs at the body sites they use for sex before starting and every 3 to 6 months after. At those visits the clinician also asks about side effects and whether you still need doxy-PEP. The tests in CDC's guidelines:

• a NAAT for gonorrhea and chlamydia at each site of exposure, which can mean urine, a throat swab and a rectal swab
• a blood test for syphilis
• an HIV test, on the PrEP schedule if you take PrEP, or every 3 to 6 months if you don't

Your prescriber or clinic usually runs these tests. If you pay for testing yourself, here's the cheapest current price on each route for a common 4 panel:

After oral or anal sex, Wisp says, a standard urine screen might miss the throat and rectum. Its 3-site home kit tests a throat swab, a rectal swab and urine for chlamydia and gonorrhea and costs $149 (verified Nov 2, 2026) at Wisp. Wisp says results come 3 to 5 business days after the lab receives the samples, and that it doesn't treat gonorrhea in the throat. Our chlamydia and gonorrhea testing guide explains the samples.

The lowest and highest price for each test, with the date we checked:

Our male STD check-up guide covers CDC's screening schedule for gay, bisexual and other men who have sex with men. If a result is positive, our positive result guide covers the next steps.

How to get a doxy-PEP prescription

• Your regular clinician. CDC suggests talking openly about the kinds of sex you have, so you can decide together and get a prescription before you need it.
• A sexual health clinic. If you'd rather not talk about STIs with your regular provider, CDC says many clinics offer confidential, free or low-cost testing and can prescribe doxycycline. CDC's Find Doxy PEP locator lists places by ZIP code.
• Telehealth, usually with PrEP. Q Care Plus says it prescribes doxy-PEP only with a first PrEP prescription or a quarterly refill. MISTR says it offers doxy-PEP free to people who get PrEP or HIV care through it, and not on its own.

Some state PrEP assistance programs also help with doxy-PEP, NASTAD says.