If your test is going to be done at a hospital and pre-screening it will probably be a full test. If this is going to be used for getting insurance then a whole battery of test will be ran and they will know you have been flushing your system and the b12 and other things can/could spike your test results.

You are very smart to have stop for the last 8 days...wtg. That's a great sign your head is level on your shoulders. I hope it is long enough to have cleared your system.

Here is an interesting page on UA's http://www.nlm.nih.gov/medlineplus/e...cle/003579.htm
It does not cover testing for drugs, but it gives you an idea of how trying to cover or hide something can be found very easy. If the test was a simple pee in the cup and then put a test strip in it to see what color it turns then some of the clean UA test kits might work.