Can warfarin cause blood in semen?

Not lilkely: Wafarin will accentuate any bleeding tendency from lesions anywhere in the body, but it would be unlikely to cause spontaneous bleeding into the sperm unless there was a lesion active in the genital tract. Hematospermia is usually a benign event but see your physician if it continues and check your inr to make sure it's in proper range.

Blood in semen: yes but you should have your inr checked to make sure it is not higher than it should be