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Jillian Stenzel

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About Author — A Nevada-bred traveler & food nerd who dances & eats spinach, sometimes simultaneously. She writes from wherever her curiosity demands, and is passionate about spreading the wisdom of better health.

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How long does PrEP take to work?

If you’re eager to get started on PrEP, you may be wondering how long PrEP takes to become effective, and how effective it is.

For anal sex, PrEP reaches maximum protection in rectal tissues after approximately 7 days of daily use.

If you are taking PrEP to prevent HIV through vaginal tissue, oral tissue or injection drug use, it will take up to 20 days.

To be safe, consume PrEP consistently for 7 days before anal sex or wear a condom your first week of taking PrEP. After your first week, continue to take PrEP daily as long as you think you are at risk for contracting HIV.

How Effective is PrEP?

In the newest studies, PrEP was found to be 99% effective, and in some studies including a Kaiser study in San Francisco, PrEP for HIV prevention was 100% effective when properly administered.

This level of effectiveness only occurs if the pill is taken every day as directed.

Missing a day drops your level of protection, though it can still be effective.

  • 7 days a week = 99% protection
  • 4 days a week = 96% protection
  • 2 days a week = 76% protection

While the level of protection is impressive for non-daily use, risking lower levels of protection and potentially contracting HIV is not worth skipping a day. Additionally, it is unclear how quickly an individual pill starts working.

Taking the pill on days you think you will have sex is not an effective method.

Should you happen to miss a dose, just be sure to take the next one. There is no need to double up.

While you don’t need to take PrEP at the same time everyday for it to be effective, doing so may prevent you from missing a day without realizing it.

PrEP can be taken with food or on an empty stomach, so consider taking it as soon as you wake up every morning or just after you brush your teeth. Incorporating PrEP into your routine will make you less likely to forget taking it.

How does PrEP work?

Many people assume that PrEP is a type of vaccine, but this actually isn’t true. Vaccines use weakened microbes to teach the body to fight off full-powered microbes.

PrEP, on the other hand, works by disrupting HIV’s ability to duplicate itself in the body, thus preventing the virus from replicating and spreading.

How can I get PrEP?

You need a prescription from a professional health care provider to take PrEP. You can meet with a doctor online from your phone or computer to start PrEP.

The online doctor will assess if you are an HIV high-risk patient and develop a treatment plan with you. If starting a PrEP program makes sense for you they will order the necessary lab tests and direct you to the nearest lab.

You will need to test HIV negative before receiving a Truvada prescription.

If you have insurance, your prescription will be covered. PrEP is also available for those who aren’t insured. There are many payment assistance programs that make the program more affordable.

Read: Insurance and Copay Assistance for PrEP

If you think you are at risk for HIV, contact your doctor or book an appointment with a PlushCare physician to learn about how you can get PrEP online.

Read More About PrEP

Sources Emtricitabine-Tenofovir Concentrations and Pre-Exposure Prophylaxis Efficacy in Men Who Have Sex with Men. Accessed October 10, 2019, at 3 Questions About PrEP. Accessed October 10, 2019, at


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