I think I may have a serious problem with my prostate or testes, as there appears to be blood in my semen. I am not in discomfort, and my testes seem normal. I have not yet seen my GP. What might be causing this? I am a pretty healthy 74-year-old.

Dr Fred Kavalier answers your health question:

Blood-stained semen (the medical name for this is haematospermia) is a frightening symptom that makes men worry about both cancer and sexually transmitted diseases. When younger men get haematospermia, it does not usually mean anything sinister, unless there are other symptoms such as pain or a discharge from the penis. The cause is usually a small blood vessel that bursts, leaking blood into the seminal fluid before it is ejaculated. Urologists have followed up men with intermittent blood-staining of the semen for many years and in the vast majority of cases it is not associated with any disease. But in a man of your age, there could be a more serious cause, such as prostate disease or even prostate cancer. You should see your GP for a check-up and examination. Your prostate should be examined and you probably should have a PSA test to look for signs of prostate cancer. You will probably end up by seeing a urology specialist.

Please mail your questions for Dr Fred to health@independent.co.uk. He regrets that he is unable to respond personally to questions.