The original site for PrEP consumers, frontline providers and clinicians


PEP, or post-exposure prophylaxis, is a course of daily medications that a person without HIV takes for 28 days AFTER a possible exposure to HIV if they weren’t taking PrEP or missed taking PrEP as prescribed. PEP must be started within 72 hours of the exposure and is more effective the sooner it’s started.

How do I know if I need PEP?

You may benefit from PEP if, within the past 72 hours, you were exposed to the pre-semen (pre-cum), semen (cum), vaginal fluid, rectal fluid, or blood from someone with an unknown HIV status or someone who has HIV and you don’t know if they are “undetectable”.

How can I get PEP?

A clinical provider must prescribe PEP. During regular office hours, ask your provider or go to a sexual health clinic. During off hours, go to an urgent care or emergency room. Many pharmacies can fill the prescription, but consider a backup pharmacy just in case.

I asked, and my provider has no idea about PEP.

If your provider doesn’t know about PEP, refer them to the federal PEP Guidelines or the national PEPline. The PEPline is only available to clinicians who need guidance on how to prescribe PEP. 

Is it expensive?

Most insurance covers the cost and patient assistance programs are available to those who are uninsured or under-insured.

The following chart may help you decide risk level and the need to take PEP.

Average Risk of HIV Transmission per Exposure to Infected Source:

Non-Sexual Modes* PercentageOdds
Blood Transfusion90%9 in 10
Needle sharing (injection drug use).67%1 in 149
Needlestick (percutaneous, thorugh the skin).30%1 in 133
Biting, spitting, throwing body fluids
(including semen, saliva), sharing sex toys
Oral Sex*PercentageOdds
Receptive partner (example: giving a blow job)0-0.04%0-1 in 2,500
Oral Sex*PercentageOdds
Receptive partner (example: giving a blow job)0-0.04%0-1 in 2,500
Insertive partner (example: getting a blow job)~0%About 0
Vaginal Sex** | Risk to female with HIV-positive male partnerPercentageOdds
High-income countries0.08%1 in 1,250
Low-income countries.30%1 in 333
Vaginal Sex** | Risk to male with HIV-positive female partnerPercentageOdds
High-income countries0.04%1 in 2,500
Low-income countries.38%1 in 263
Anal Sex***PercentageOdds
Insertive partner’s risk (circumcised)0.11%1 in 909
Insertive partner’s risk (uncircumcised)0.62%1 in 161
Receptive partner’s risk (without ejaculation)0.68%1 in 154
Receptive partner’s risk (with ejaculation)1.43%1 in 70

* J Fox, et at, Quantifying Sexual Exposure to HIV within an HIV-Serodiscordant Relationship: Development of an Algorithm. AIDS, 2011.

** Summarized from Boile MC, et al, Heterosexual Risk of HIV-1 Infection Per Sexual Act: Systematic review and meta-analysis of Observational Studies. Lancet Infect Dis 9: 118-29, 2009.

*** Jin F, et al, Per-Contact Probability of HIV Transmission in Homosexual Men in Sydney in the Era of HAART. AIDS, 2010.