Do STIs cause bleeding from the genitals?

Some can, usually by inflaming the cervix or the lining of the bottom. These are the main ones:

• Chlamydia: bleeding after sex or between periods, and pain, bleeding and discharge from the bottom.
• Gonorrhoea: bleeding between periods, although this is rare.
• Mycoplasma genitalium: bleeding after sex in women.
• LGV (lymphogranuloma venereum), a type of Chlamydia: bleeding from the bottom.
• Genital warts: these may sometimes bleed.

Many people with these infections have no symptoms at all, so bleeding is only one possible sign. Read more in “Is blood in urine a symptom of an STI?”

Chlamydia can inflame the cervix, which can cause bleeding after sex or between periods. Gonorrhoea rarely does this, and Mycoplasma genitalium has been linked with bleeding after sex.

Bleeding after sex or between periods has many other causes, including:

• hormonal contraception, like the pill
• changes to the surface of the cervix (cervical ectropion)
• small growths, like polyps or fibroids
• vaginal dryness

Unusual vaginal bleeding, including bleeding during or after sex, between periods or after the menopause, can also be a symptom of cervical cancer. These symptoms are very common and usually caused by something else, but always get them checked by a doctor.

STIs rarely cause visible bleeding from the penis. The NHS doesn’t list bleeding from the penis as a symptom of Chlamydia or Gonorrhoea, although both can cause discharge and pain when you pee.

Blood in your semen isn’t usually caused by something serious. STIs and urine infections are possible causes, along with recent procedures, like a vasectomy, and prostate problems. See a doctor to find out why.

Blood in your pee needs checking more urgently, as it can be a sign of cancer. Get urgent medical care if you have, or think you have, blood in your pee.

Rectal Chlamydia and Gonorrhoea often cause no symptoms. When they do, Chlamydia can cause pain, bleeding and discharge from the bottom, and Gonorrhoea can cause discharge and pain.

LGV, a type of Chlamydia, is most often seen in gay, bisexual and other men who have sex with men in England, where it usually infects the bottom. It can cause pain, bleeding and discharge from the bottom. There were 1,252 diagnoses in men in England in 2024.

Bleeding from the bottom has many other causes too, including piles, small tears (anal fissures), damage from anal sex, genital warts, inflammatory bowel disease and, less often, bowel cancer. Read more in “Is unprotected anal sex dangerous?”

A few other infections are often mentioned alongside bleeding:

• Herpes causes small blisters that burst to leave red, open sores around the genitals or bottom.
• Syphilis usually starts with a painless sore, which may be on the penis, in or around the vagina, or around the bottom.
• Trichomonas can cause discharge, soreness and pain when you pee or have sex, but the NHS doesn’t list bleeding as a symptom.
• Ureaplasma is often found in people with no symptoms, and UK guidance doesn’t link it with bleeding.
• HPV doesn’t usually cause symptoms, apart from genital warts, but some types can lead to cervical cancer, which can cause bleeding.

Cervical screening checks for high-risk HPV to help prevent cervical cancer. It isn’t a test for cancer, so don’t wait for your next screening if you have unusual bleeding.

Get urgent medical care if:

• you have missed a period and have unusual vaginal bleeding and pain in your tummy, as this can be a sign of an ectopic pregnancy
• you’re pregnant and have any bleeding, even light spotting
• you have blood in your pee
• your poo is black or dark red, or you have bloody diarrhoea

In an emergency, call 999, including if:

• you’re pregnant and bleeding heavily, or bleeding with severe tummy pain, shoulder pain or feeling faint
• bleeding from your bottom won’t stop or is heavy

See a doctor if you have any bleeding after the menopause, even a small amount.

If you think an STI could be causing your bleeding, Better2Know offers:

• Comfort Screen: tests a urine sample for 8 infections that can cause genital symptoms: Chlamydia, Gardnerella, Gonorrhoea, Herpes 1, Herpes 2, Mycoplasma, Trichomonas and Ureaplasma. You can test from 14 days after sex, with results in 2 days at a clinic, or order a Comfort Screen home test.
• Full Screen: tests for 7 infections, including Chlamydia, Gonorrhoea, HIV, Syphilis and Mycoplasma, from 28 days after sex, with results in 3 days. If you test before 45 days, a negative HIV result needs a repeat test. A Syphilis test in the first 3 months after sex can miss the infection, so you may need a repeat test.
• Chlamydia and Gonorrhoea (Rectal Swab): if you’re bleeding from the bottom after anal sex. You can test straight away if you have symptoms, or from 14 days after sex if you don’t, with results in 2 days.
• Blemish Screen: if you have a sore, blister or wart, a swab tests it for Herpes 1, Herpes 2, HPV and Syphilis, with results in 5 days.

An STI test can’t rule out other causes of bleeding, so always get unusual bleeding checked by a doctor too. Not sure which test you need? Our Patient Care Team is available 24/7 on 020 7099 0955.

Can Chlamydia cause bleeding after sex?

Yes. In women, Chlamydia can inflame the cervix and cause bleeding after sex or between periods. Many people with Chlamydia have no symptoms, though.

Is it normal to bleed a little after sex?

Light bleeding after sex can have harmless causes, like vaginal dryness or cervical ectropion. It’s not usually serious, but it’s always worth getting it checked by a doctor.

Can an STI cause blood in semen?

It can. STIs are one possible cause of blood in semen, along with urine infections, prostate problems and recent procedures. See a doctor to find out why.

Some STIs, especially Chlamydia, can cause bleeding after sex, between periods or from the bottom. But bleeding has many other causes, most of them not serious, so don’t assume it’s an STI, or that it isn’t. Call 999 for heavy bleeding in pregnancy or from the bottom, get urgent medical care for any other bleeding in pregnancy, and see a doctor about any unusual bleeding.

Book a Comfort Screen at a clinic near you or order a home test kit from 14 days after sex. 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 20 September 2024 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 29 October 2024. It is general information and not a substitute for personal medical advice.

Sources

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