I am a heavy smoker of both marijuana and cigarettes. after smoking marijuana, i tried to stand up and walk. my vision went black and i fainted.

OK, STOP: Marijuana is illegal in many countries for a reason. It is a mind altering substance. You should not smoke regular cigarettes for all the known reasons, and you should stop smoking pot too. See a dr. For an evaluation and check up since you fainted. Good luck.

Please stop/cut back: Fainting after standing is generally caused by low blood pressure and marijuana is known to lower blood pressure. I urge you to stop smoking cigarettes asap- i don't understand why anyone would do this given its terrible effects on health- see http://1.Usa.Gov/1jvuqkn while marijuana is not nearly as harmful ; can even have some health benefits, i think it is far safer when used in moderation.