Im not exactly sure about how you would go about passing a blood test or how long it even stays in your blood. I do know that there are ways to pass a urinalysis. I am currently on probation for a possession charge and get weekly piss tests. The best method Ive found is to use Urinary Tract Infection pills by the name of AZO Standards and AZO Cranberries. On different occasions I have smoked the day before my test and still managed to pass using these pills.

What I did to pass:
-stop smoking from the time you find out you have a test
-take 4 AZO standards and 4 AZO cranberries night before your test before you go to bed
-take 4 AZO standards and 4 AZO cranberries morning of test(give yourself anywhere from 4-5 hours as it will make your urine lots of different colors)
-follow N2's sticky on dillution if you want to be cautious/ drink plenty of water, gatorade, and fluids

It has yet not to work for me.. Hope it helps..