 [ Symptoms ] what over the counter drugs interfere with drug tests [ Disease ] the list would be too extensive to post so my advise to you is not to take any over the counter medications if you are having a blood test unless they are essential to your health and well being i do not know what you are taking and why nor do i know what type of drug screening test you are getting if you do take or have recently used illegal drugs i can tell you that tests are becoming more and more sophisticated all of the time