When you ask the question â??How high would my level be?â?ť you need to take into account the fact that there is no simple answer to this question. Quite simply, itâ??s argued both that THC never leaves your brain, as well as that there are several different factors which can affect-speed of your metabolism, hight, weight, how much marijuana you smoked. It's best to speak with a doc/professional. And if youâ??re worried about testing positive for marijuana, then you should definitely invest in some of the great products that will help you to test negative.