Can Marijuana be manipulated if you know you are going for blood tests?
Marijuana cannot be manipulated. There may be things you can ingest that will mask the presence of the active ingredient, TCP, but there is no guarantee as all bodies and metabolisms differ.
Stop smoking the stuff. If you fail the drug test, schedule another one. Don't smoke for a month or more. Take the test again. If you fail again, ask for another test. Don't smoke. Eventually you will be clean. Stay that way. It's not worth the worry or the toll it takes on your body and your psyche. Be smart and think clearly. You'll be a better person for it.
No. The THC, the active ingredient in marijuana cannot be manipulated as a chemical. However, you can cleanse your body of the chemical faster than it can be metabolized naturally. Drink alot of water and get a natural cleanse to expel the chemical from your body.
The best advise is to stop ingesting the drug altogether. Typically a chronic smoker, one who smokes everyday, will need 30 days to rid it from your body. However, everyone is different.