Possible hair test

I am scheduled for a pre-employment medical examination next week and am suspecting a drug screen. The physician that I am being sent to offers both urine and hair tests so I am not sure what to expect. I am clean enough now to pass a urine test, but not a hair test.

Can I call the facility and request information about the examination and find out what exactly it will be? Can they tell me if a drug screen will be included and if it will be urine or hair? Will calling the facility raise any flags and can my inquiry get back to my employer? Is there a certain way I should word my question? Should I go ahead and take the necessary steps to prepare for a hair test just in case? From my other thread I learned that I cannot request the results of the drug screen since I am not paying for it, but do I have the right to ask what exactly will be performed on me?

Please help!