STIs and blood in semen

Educational information only, not a diagnosis. Know when to get help.

Sexually transmitted infections are among the known, treatable causes of blood in semen [NHS] [Cleveland Clinic]. In men under 40, infection of the urinary or genital tract is the most common identifiable cause [review].

Which infections?

Cleveland Clinic lists gonorrhea, chlamydia and other viral or bacterial infections [CC]. Many STIs, including chlamydia, often cause no symptoms at all [NHS], so testing is the only way to know.

Getting tested

• Sexual health clinic or your doctor. Testing is usually a urine sample and sometimes a swab or blood test [NHS].
• At-home kits. Mail-in kits let you collect a sample at home and get results online. Positive results should be followed up with a clinician for treatment.

If you test positive

Most bacterial STIs are treated with antibiotics. Recent partners may also need testing and treatment [NHS] [NHS]. Avoid sex until you and your partner have finished treatment, as advised by your clinician.

NICE notes most causes of blood in semen don't affect fertility, except STIs such as chlamydia or gonorrhea, which is one more reason to test and treat promptly [NICE].