Hello Michael. Thanks for asking on Healthcaremagic. Blood in semen commonly might occur due to any internal injury which might get relieved on its own in due course of time. Other ominous causes which are more common in old age are tumors or infections including tuberculosis. However in developed countries tuberculosis is not that common. Wait for some days and then get your semen analysis done in any reputed lab. The finding might suggest infection if associated with increased pus cells. Or it might clear up by then. Thanks