Is unprotected anal sex dangerous?

It carries a higher risk than most other types of sex. The lining of the anus and rectum is thin and easily damaged, which makes it easier for STIs to pass on.

For HIV, receptive anal sex (being the bottom) carries the highest risk of any type of sex. If your partner has HIV and isn’t on effective treatment, the estimated risk is about 1.4% each time you have receptive anal sex without a condom, and about 0.1% for the partner who penetrates.

The real risk depends on your partner and how you protect yourself. It’s much lower with a condom, and there’s no risk of HIV from a partner who has an undetectable viral load.

A few things make anal sex riskier than vaginal or oral sex:

• The anus doesn’t make its own lubrication, so the skin tears easily, and small tears can let infections in.
• The lining of the rectum is thin and absorbs fluids, including pre-cum and semen.
• The rectal lining is rich in cells that HIV can infect directly, even when there’s no damage.

The partner who penetrates is at risk too. HIV can enter through the opening at the tip of the penis and the skin under the foreskin, from rectal fluids or blood.

Anal sex without a condom can pass on:

• Gonorrhoea and Chlamydia, including LGV, a type of Chlamydia seen mainly in gay and bisexual men
• Syphilis
• Herpes
• HPV, which can cause anal warts
• Hepatitis B and, less often, Hepatitis C, which is more likely to pass on during sex that causes bleeding
• Hepatitis A, Shigella and other gut infections, which pass on through rimming or unwashed hands

Chlamydia, Gonorrhoea and Syphilis are treated with antibiotics, and Hepatitis C can usually be cured with tablets. HIV, Herpes and long-term Hepatitis B can’t be cured, but treatment keeps them under control, and most people with HIV who have treatment live a long and healthy life.

Most infections in the bottom cause no symptoms. In one large study of gay and bisexual men, about 85% of rectal Chlamydia and Gonorrhoea infections had no symptoms, so you can’t rely on symptoms to tell you you’re clear.

When there are symptoms, they can include:

• pain or discomfort in your bottom
• discharge or bleeding from your bottom
• itching around your anus
• sores, blisters or lumps around your anus

A Syphilis sore is usually painless, so it’s easy to miss. Read more in “I have an itchy anus. Could it be an STI?”

These steps make anal sex safer:

• Use a condom with plenty of water-based or silicone-based lube. Don’t use oil-based products like Vaseline with latex condoms, as they can make them split.
• You don’t need a special thicker condom. A UK trial found standard condoms were just as reliable for anal sex.
• Use a new condom, and wash your hands, if you move from anal to vaginal sex.
• Don’t share sex toys. If you do, wash them and put a new condom on them before anyone else uses them.
• Use a dam (a thin latex square) over the anus for rimming.
• If you’re at higher risk of HIV, ask about PrEP, tablets that greatly lower your chance of getting HIV.
• If you’re a gay or bisexual man, you can get vaccines against Hepatitis A, Hepatitis B and HPV (up to the age of 45), and a vaccine that gives some protection against Gonorrhoea if you’re at higher risk.

Read more in “Can condoms fail without breaking?”

If you’ve had anal sex without a condom:

• You may need PEP, emergency HIV medicine, if your partner has HIV and doesn’t have an undetectable viral load, or you don’t know their status and they’re from a group with higher HIV rates. It must be started within 72 hours, and ideally within 24 hours, so get urgent medical care straight away.
• Test for Chlamydia and Gonorrhoea from 2 weeks after sex. After receptive anal sex, you need a swab from your bottom, which you can usually take yourself, because a urine test only checks your genitals.
• The HIV tests in the screens below can be taken from 28 days after sex. UK guidance says a lab test is reliable from 45 days, so if you test earlier and your result is negative, test again.
• A Syphilis test in the first 3 months after sex can miss the infection, so you may need a repeat test.

Read more in “What is PEP and how does it work?”

Better2Know offers:

• Full Screen: tests for 7 infections, including Chlamydia, Gonorrhoea, HIV, Syphilis and Hepatitis B, from 28 days after sex, with results in 3 days (5 days for the home test). If you test before 45 days, a negative HIV result needs a repeat test. You can book it at one of our clinics or order a Full Screen home test.
• Chlamydia and Gonorrhoea (Rectal Swab): a swab from your bottom for anyone who has had receptive anal sex, from 14 days after sex, with results in 2 days. You can book it at one of our clinics or order it as a home test kit.
• Confidence Screen: the Full Screen plus throat and anal swabs for Chlamydia and Gonorrhoea, from 28 days after sex, with results in 5 days. If you test before 45 days, a negative HIV result needs a repeat test. It is designed for gay and bisexual men, and you can also order a Confidence Screen home test.
• Platinum Screen: our most comprehensive STI screen. It tests for 12 infections, adding Hepatitis C, Herpes 1, Herpes 2, Trichomonas and Gardnerella to the Full Screen, from 28 days after sex, with results in 3 days. If you test before 45 days, a negative HIV result needs a repeat test.

The Full Screen and Platinum Screen test your urine for Chlamydia and Gonorrhoea, which only checks your genitals, so if you were the bottom, add a rectal swab. Not sure which test you need? Our Patient Care Team is available 24/7 on 020 7099 0955.

Is anal sex safe with a condom?

It’s much safer. Used correctly with plenty of lube, condoms greatly lower the risk of HIV and most other STIs. But infections that spread through skin contact, like Herpes, HPV and Syphilis, can still pass on if the condom doesn’t cover the affected skin. Read more in “3 STIs you can catch even if you use a condom”

Can you get HIV from anal sex if your partner is undetectable?

No. A person with HIV who takes effective treatment and has an undetectable viral load can’t pass HIV on through sex, including anal sex without a condom. This is known as U=U, or undetectable equals untransmittable. Condoms still protect you against other STIs.

Can you get an STI from rimming?

Yes. Rimming (oral sex on the anus) can pass on gut infections like Hepatitis A and Shigella, as well as Herpes. Using a dam lowers the risk. Read more in “Can you get an STI from rimming?”

Unprotected anal sex carries a higher risk of HIV and other STIs than most types of sex, and most infections in the bottom cause no symptoms. Condoms, lube, PrEP and a partner’s undetectable viral load all make it much safer.

If you’ve had anal sex without a condom, get tested. Book a Full Screen at a clinic near you or order a home test kit. If you were the bottom, add a Chlamydia and Gonorrhoea rectal swab, or choose a Confidence Screen if you’re a gay or bisexual man. Our Patient Care Team is available 24/7 on 020 7099 0955.

Not in the UK? Choose your country from the selector at the top of the page for local tests and prices.

This article originally appeared on 13 October 2023 and was last updated on 30 September 2026.

Medical review. This article was medically reviewed by Dr Steve Chapman, Doctor with a wealth of clinical experience in the field of STIs, on 2 October 2025. It is general information and not a substitute for personal medical advice.

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