Will marijuana thin your blood? I have recently had an opperation and am not able to take any medications that cause your blood to thin such as asprin, IB profin, and most over the counter drugs. The pain relievers the doctor gave me only suceed to increase my naseua and pain. I was considering trying MJ to alleviate the pain but my surgery will not heal correctly if it thins the blood. Anyone ever researched this or know anything about this issue?