Well lets see, he's 23 or 24. My best friend's brother. He is a huge cheezle-beezle. He said he stopped smoking for 3 to 4 days and took a lot of B vitamins. So I'd say like 4 a day for several days? That test pure, that's all it is. And I drank the bottle stated "for larger persons or persons with higher toxin levels" It also asks that you stay away from toxins or other acidy drinks that would confuse the test. The test was through LabCorp, huge! huge!