Is there more risk of contracting HIV during anal sex?

Mike Bohl, MD, MPH, ALM - Contributor Avatar

Written by Gerrie Lim, MPH 

Mike Bohl, MD, MPH, ALM - Contributor Avatar

Written by Gerrie Lim, MPH 

last updated: Jul 30, 2020

5 min read

The Centers for Disease Control and Prevention (CDC) recommends everyone ages 13 to 64 gets tested for HIV at least once in their lives. While certain demographics, like men who have sex with men (MSM), have an increased risk of infection, anyone can have HIV. Most cases of HIV are transmitted sexually, and most notably, through the act of anal sex.

The human immunodeficiency virus, or HIV, is a virus that attacks a specific type of white blood cell in your immune system. By targeting CD4 cells or helper T cells, HIV can make it difficult for your immune system to coordinate a response. Through this mechanism, the virus renders your body more prone to disease and infection (AIDS info, n.d.

HIV can be transmitted through bodily fluids of someone with HIV, including blood, breast milk, pre-seminal fluid, semen, rectal fluid, or vaginal fluid. Though HIV testing can be conducted through an oral swab, HIV is not transmittable by saliva. The virus is most commonly spread through unprotected (condomless) sex as a sexually transmitted infection (STI) or by sharing needles (, 2020). 


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What makes HIV transmission risk higher with anal sex?

While the risk of HIV transmission varies according to sexual activity, unprotected anal intercourse, or the insertion of the penis into the anus, carries the highest risk, especially without the use of condoms. During anal sex, the person with the penis is called the insertive partner, and the person receiving the penis is called the receptive partner.

A study by the CDC found that out of 10,000 cases of HIV, 138 of them contracted the virus through being the receptive partner in penile-anal sex, as opposed to the eight people who contracted the virus through being the receptive partner in penile-vaginal intercourse (CDC-b, 2019; CDC-a, 2019). The high risk has to do with the thinness of the rectum lining. Thus, it’s important to note this is the anatomy of anyone with a rectum lining, not just MSM. The rectum is lined with a single layer of columnar mucosal epithelium, which is prone to tearing from repeated movement. Wounds allow the virus to enter directly into the bloodstream. As part of the gastrointestinal tract, the rectum houses a majority of lymphocytes that HIV targets, such as CD4 immune cells (Kelley, 2017).

However, the insertive partner can still be at risk for contracting HIV. The virus can enter the insertive partner’s body through the opening of the penis (urethra) or through cuts, scratches, or sores on the penis. Studies have found that circumcision can decrease the chance of HIV infection by 50–60%, but, like the rectum, the inner foreskin and urethra are lined with vulnerable cells called mucosal “wet” epithelial cells. These cells have a thinner protective keratin layer than most epithelial cells, making them particularly susceptible to HIV infection (Anderson, 2011).

Semen and pre-seminal fluid both have high concentrations of the virus. Studies show that even with antiretroviral therapy (ART), people living with HIV still had detectable levels of the virus in their semen. However, it’s important to note that one study conducted found that this was the case because participants had poor adherence to their HIV regimen (Politch, 2012). It’s important to follow your healthcare provider’s directions and use protection during sexual intercourse. 

What are some tips for practicing safe anal sex?

Use protection

Condoms are highly effective at preventing the spread of HIV and other sexually transmitted infections (STIs) like gonorrhea or chlamydia. Condoms are more than 90% effective in protecting sexual partners from transmission (Marfatia, 2015). Condoms do their best work when they are worn correctly and consistently. 

While using condoms is one of the best forms of protection, they could still tear or may have holes. If you think you have been exposed to HIV despite wearing a condom, get tested and find out your HIV status. Use condoms in combination with other forms of protection like pre-exposure prophylaxis (PrEP) and ART.

Avoid having sex during times that you may be at increased risk

HIV transmission risk is typically very low in sexual activities like oral sex. However, oral sex can still pose a risk. Because HIV can be transmitted through bodily fluids like blood, avoid unprotected oral sex when oral ulcers, bleeding gums, genital sores, and the presence of other STIs. Using protective barriers, such as dental dams and condoms, can significantly reduce the risk of transmission (CDC-c, 2019).

Pre-exposure prophylaxis (PrEP)

PrEP is an HIV prevention method in which someone who does not have HIV takes medication daily to reduce their chances of getting infected if exposed to the virus. PrEP can stop HIV from permanently establishing itself in a person’s body. In the United States, there are currently only two FDA-approved medications for PrEP. They are emtricitabine and tenofovir disoproxil fumarate (sold as Truvada) and emtricitabine and tenofovir alafenamide (sold as Descovy) (, 2019). 

The FDA-approved option of taking PrEP every day can reduce the risk of contracting HIV during sex by 99% and the risk of contracting HIV through an infected needle by 74%. PrEP is significantly less effective if it is not taken every day. It’s important to note PrEP only protects against HIV, not other STIs (, 2019). However, some clinicians may recommend a “2-1-1” dosing approach to PrEP if you engage in anal sex, which means taking two pills before condomless sex, one pill 24 hours later, and one more pill 24 hours after that. Talk to your healthcare provider before attempting this. 

Post-exposure prophylaxis (PEP)

Post-exposure prophylaxis, or PEP, is an emergency measure for people who do not have HIV but think they have been exposed in a single, high-risk incident. It is a short course of HIV medicines taken as soon as possible after the exposure. It is most effective when started within 72 hours and is not meant for regular, constant use (, 2019). 

If you think you have been exposed to HIV, contact your healthcare provider as soon as possible or go to an emergency room. Time is of the essence when it comes to PEP. In the average PEP regimen, you will need to take the medications every day for 28 days straight. At the end, you will need to follow up with your healthcare provider with an HIV test to check your status. PEP is effective when taken correctly, but it is not 100% (, 2019).

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Antiretroviral treatment (ART)

Antiretroviral treatment, or ART, helps people manage HIV through a combination of different HIV medications every day.

Some HIV medications prevent the virus from replicating itself, while others prevent entry into the cell. The amount of HIV in the body is called the viral load, which is one of the best ways to measure HIV progression. The more HIV a person’s body has, the weaker their immune system will be. Besides the benefit of managing HIV, ART can lower the level to an undetectable viral load, meaning an HIV-positive person has effectively no risk of transmitting HIV to their HIV-negative partners through sex (AIDS Info, 2020).

If you test positive for HIV, you should start taking HIV medications as soon as possible. HIV can progress to autoimmune deficiency syndrome (AIDS), a condition that greatly lowers life expectancy. Starting ART early and adhering to the medication regimen can help people with HIV live longer and healthier (AIDS Info, 2020).

Get tested regularly

The only way to be sure of your HIV status is to get tested. In the United States, it’s estimated that one in seven people who have HIV do not know their status. If your behavior puts you at risk, you should get tested often.

If you’re trying to decide if you should get tested, ask yourself:

  • Have you injected drugs or shared needles with others?

  • Have you been diagnosed with or sought treatment for an STI?

  • Have you been diagnosed with or sought treatment for pneumonia or tuberculosis?

  • Have you been sexually assaulted?

  • Have you had more than one sexual partner?

  • Are you curious what your HIV status is? 

If you answered “yes” to any of these questions, you should get tested. 

  • Do you use protection when you engage in sexual intercourse?

  • Do you know the HIV status of all your sexual partners?

  • Do you know how your sexual partners would have answered the previous questions?

If you answered “no” to any of these questions, you should get tested. 

You can get tested by asking your healthcare provider, finding a local health clinic, or buying an at-home kit. It’s important to know your status and communicate it to your sexual partners. By starting the conversation, you can create a safe space for someone to disclose their status.


If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

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Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

July 30, 2020

Written by

Gerrie Lim, MPH

Fact checked by

Mike Bohl, MD, MPH, ALM

About the medical reviewer

Dr. Mike is a licensed physician and a former Director, Medical Content & Education at Ro.