Play hardball, emphasize that it's the principal of the thing. If pressed make it clear that you would have serious reservations about working at a company that treats its employees this way. This is probably your best bet. Nothing to loose, and if executed properly gives you a good reason for refusing the test. 2022. 5. 23. · Discussed here are twelve things that can make a person fail a drug test: 1. Vitamin B Supplements. Vitamin B12 is essential for the proper functioning and development of organs like the brain, blood cells, nerves, and other vital organs of the human body. Some natural herbs contain vitamin B complex supplements that can lead to false-positive.