References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
Anal sex carries a higher risk of HIV transmission than vaginal or oral sex. The lining of the rectum is thin and has a rich blood supply, which makes it easier for HIV to enter the body. Understanding the risk — and the many things you can do to reduce it — helps you make informed choices.
Here’s what the evidence says about risk levels, and the most effective ways to protect yourself and your partners.
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Why Is Anal Sex Higher Risk?
- The rectal lining is just one cell thick in places
- Small tears are common during anal sex, even without any pain
- The rectal mucosa has many immune cells that HIV can infect directly
- There is no natural lubrication in the rectum
Relative Risk by Role
| Activity | Risk Level |
|---|---|
| Receptive anal sex (bottom) | Highest per-act risk |
| Insertive anal sex (top) | Lower than receptive, but still higher than vaginal |
| Oral sex | Very low |
| Mutual masturbation | Essentially no risk |
Per-act risks are population averages and depend heavily on viral load, condom use, PrEP use, the presence of other STIs, and whether there is bleeding or trauma.
Things That Increase Risk
- Detectable HIV viral load in the positive partner
- No condom use
- Not using PrEP
- Other STIs (especially ulcerative infections like syphilis or herpes)
- Bleeding or visible trauma
- Recent acute HIV infection (very high viral load)
How to Reduce Risk
U=U (Undetectable = Untransmittable)
If the HIV-positive partner is on effective treatment with a sustained undetectable viral load, HIV cannot be passed on. This is one of the most effective protections available.
PrEP
Pre-exposure prophylaxis taken as prescribed reduces the risk of HIV acquisition by over 99%. It’s free on the NHS through sexual health clinics.
Condoms
Condoms used correctly every time provide very high protection. Always use plenty of water or silicone-based lube to reduce the risk of breakage and small tears.
Post-exposure prophylaxis (PEP)
If you think you’ve had a high-risk exposure and aren’t on PrEP, PEP is emergency HIV medication that can stop infection if started within 72 hours. It’s available free from sexual health clinics and A&E.
Regular STI testing
Treating other STIs promptly lowers HIV risk. If you’re having anal sex with new or multiple partners, testing every 3 months is a good routine.
Lubricant Matters
Use a generous amount of water-based or silicone-based lubricant. Never use oil-based lube with latex condoms — it breaks them down quickly. Lube reduces friction, tiny tears, and pain, all of which lower risk.
Read more: What is HIV? | Do condoms protect against HIV? | PrEP benefits and risks
Frequently Asked Questions
Is receptive anal sex always high risk?
It’s the highest per-act risk on average, but actual risk depends on PrEP, viral load and condom use. If your partner is undetectable, there is no sexual transmission risk, even without condoms.
How long do I have to take PEP after a risky exposure?
PEP must be started within 72 hours of exposure. The sooner the better. Contact a sexual health clinic or A&E as soon as possible.
Can I get HIV from topping?
Yes, but the per-act risk is lower than for the receptive partner. Condoms, PrEP and U=U all protect both partners.
Related reading
- Can You Catch an STI From a Toilet Seat?
- Can You Get Chlamydia From Kissing?
- Can You Get Herpes From a Toilet Seat?
- Can You Get Herpes From Kissing?
- Can You Get an STI if You're Both Virgins?
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
