We need some more info, like height, body type and what kind of test like preemployment, probation, military, random, insurance ect. Then you have to make a decision wheather to sub or dillute. If your test is one week after the 15th you will have not quite 3 weeks clean. You may be able to dillute depending on your body type, but it is risky. Substituion works every time if you are careful, practice and are not observed. Post back after doing some reading with some info on your situation and someone will try to point you in the right direction.
STIMPY21