Semen may contain small amounts of blood if you have recently suffered damage to your penis or testicles. Blood vessels in the testicles can occasionally become damaged and burst even without being physically struck, causing a short-term appearance of blood. You may also notice blood in your sperm for a short time after undergoing medical procedures like vasectomy and biopsy test for prostate cancer. Blood in your semen may be a minor condition, but In rare cases it can also be a sign of prostate or testicular cancer. Seek immediate medical attention for testing and treatment if blood appears in your semen for more than 7 days.
Attribution: Straight Talk Foundation