I'm a nurse and every job I take involves pre-employment drug testing. Asking if they require one sends a red flag to any HR personel. Alot of times the drug testing is done at the facility when you recieve your MANTOUX(T.B.)test. If you have legal prescriptions for your medications you'll just have to show proof. That info is and should be completely confidential due to HIPPA laws which protects the privacy of anyones private medical history, Good-luck and enjoy your new job