Truvada as PrEP (pre-exposure prophylaxis) is a pill taken each day to prevent HIV. Among men, daily PrEP use reduces the risk of HIV by 99 percent or more; among women, that figure is estimated to be more than 90 percent (indeed, it may be greater but more research is needed). For individuals engaging in anal sex, PrEP must be taken for a week prior to sex for maximum protection; for those engaging in vaginal sex, PrEP must be taken for 30 days before sex.

So that—in a nutshell—is PrEP and how to take it. But what if you’ve been on the medication and want to stop? Maybe you’re in a monogamous relationship with someone who is HIV negative or are no longer having sex or there’s some other reason.

While you should always consult with your PrEP provider first, you should continue to take PrEP for a month after the last time you had sex and get tested for HIV four weeks after. This gives the medication time to eradicate the virus in the event that you have been exposed; the HIV test will simply confirm your HIV status.

Should your circumstances change, don’t worry: As long as you’re HIV negative, you can safely restart taking PrEP. Remember to take the med for a week before having anal sex and for a month before vaginal intercourse.