They are within their rights to ask you to take a simple drug test in order to comply with their program. Take the test so they can be sure they are treating you correctly and safely. Shouldn't be a problem if you aren't using/abusing drugs. If you don't wish to comply with their requirements, then you can leave their program. If this is related to your illnesses (I thought those hadn't been all officially diagnosed, that those are your own self-diagnoses), you could also have your treatment team consult with the specialist who are working with you for those chronic illnesses to explain how those symptoms may be presenting themselves.