B.C. powder is just asprin pain reliever, which I have been told can possibly interfere with the drug test. I don't think taking any asprin is necessary, but if you have one around it's better safe than sorry. You can find Certo (or SureJell) at any grocery store, usually in the same vicinity as jello. It should not cost you any more than $3.50, and it'll probably be much cheaper than that.