Blood in the semen is medically known as hematospermia, which may be related to chronic seminal vesiculitis, prostatitis, prostate cancer, etc. 1. Chronic seminal vesiculitis: pathogens from urethral infections enter the seminal vesicles retrogradely through the ejaculatory ducts, or travel up the vas deferens from the epididymis to the seminal vesicles. There will be bleeding of the endothelial cells on the surface of the seminal vesicles, often manifested as hematospermia, which may be accompanied by hypogonadism and other manifestations. 2. Prostatitis: severe prostatitis can lead to obvious prostate congestion and edema, resulting in bleeding. Prostate fluid is also a component of semen, so hematospermia may also occur. 3. Prostate Cancer: The prostate is relatively close to the seminal vesicles, and when a tumor develops in the prostate, it is likely to invade the seminal vesicles. This will cause the blood vessels of the seminal vesicles to rupture and bleed, resulting in the appearance of hematospermia. It is recommended to consult a doctor for further examination and to clarify the cause with the help of the doctor, and to carry out targeted treatment or therapy.