Ive been on about 12 to 16mg of suboxone a day fir nearly 5 years; if i stop 48 hrs before a blood tox screen, will i pass?

No. : Suboxone will still be in your system after 48 hours. However, they will need to test your urine specifically for Suboxone as it will not come up in a routine urine drug screen.

Is it prescribed: and, if so, why the variation in the dose. There should not be a range of medication you take, but a fixed dose. If it is being appropriately prescribed, then that is a defense against a drug test. Secondly, are you sure they are doing a blood test, since blood testing is the WRONG way to determine whether someone is using suboxone. They also have to test for specific drug with buprenorphine.