Bleeding in semen caused by medical procedures, also known as hematospermia. Blood in semen caused by infections, tumors, and stones in organs as well as anatomical problems. The most common cause is a prostate biopsy.
Sexually transmitted infections (STIs) or sexually transmitted diseases (STDs) are usually acquired through sexual contact. The organisms (viruses, bacteria, or parasites) that cause STIs may pass from person to person in semen, vaginal fluids, blood, or other bodily fluids.