I have a blood test coming up. They are testing my levels of oxycodone. Does anyone know how far back they can test the levels for, is it days or weeks? I'm supposed to take 4 a day. On my very horrible days I take up to 6 or 7. Sometimes that's 3 or 4 days in a row. And other days I only have to take maybe 3. Which is why I'm asking.