Blood in semen: causes, red flags and when to get it checked

Semen passes through the prostate and seminal vesicles, which are rich in small blood vessels. Inflammation, minor injury or a recent procedure can cause small amounts of bleeding that discolours the semen pink, red or brown. Most of the time it is a one-off.

• Idiopathic: no cause found, common in men under 40, resolving within weeks.

• Prostate or seminal vesicle inflammation or infection, including STIs such as chlamydia.

• Recent prostate biopsy, vasectomy or urological procedure, or a long period without ejaculation.

• Injury or vigorous sexual activity or exercise.

• Urinary tract infection, epididymitis or urethritis.

• High blood pressure, clotting disorders or anticoagulant medicines.

• Prostate enlargement and cysts or stones in the seminal vesicles.

• Prostate or testicular cancer, which is uncommon but a consideration in older men or with other symptoms.

Age over 40, persistent episodes beyond a few weeks, recurrent episodes, blood in urine, pain, a weak stream, testicular lump or swelling, unexplained weight loss, bone pain, fever, a family history of prostate cancer and bleeding problems elsewhere warrant further assessment.

• Same-day GP or urgent care: blood in semen with fever, severe pain or inability to pass urine.

• GP within days to weeks: blood in semen with blood in urine, testicular lump, or in a man over 40.

• GP: recurrent episodes or persistence beyond a few weeks.

• Routine: a single episode in a young man, with no other symptoms.

The doctor asks how many episodes, duration, recent procedures or sexual activity, urinary symptoms, pain, fever, STI risk, bleeding tendency, medicines and family history. They check blood pressure, examine the abdomen, genitals and prostate, and may take urine and swabs.

• Blood pressure and urine dipstick and culture.

• STI screen: swabs and urine tests.

• PSA blood test in men, following counselling about its limits.

• Scrotal or transrectal ultrasound and, occasionally, MRI of the prostate.

• Cystoscopy: if there is blood in the urine or persistent unexplained episodes.

Most single episodes clear on their own within a few weeks. Avoid vigorous ejaculation or sexual activity until it settles, complete any antibiotic course, and attend for review if it recurs. Keep track of episodes and any associated symptoms. Use condoms until infection is excluded.

The NHS route is a GP, with urology referral for persistent or high-risk cases. Private urology offers direct access to examination, ultrasound and PSA.