Umm, obviously if you have abnormally low blood pressure then smoking weed is not going to be a good idea. Substantial loss in blood pressure usually only occurs after getting shit faced though. Like so baked you can't stand up. Getting that high when you A. Do not smoke very often and/or B. When you have low blood pressure would not be the greatest idea. I'm not saying a joint is going to kill someone with hypotension. But if the conditions are right, I can see it happening.