Pre employment drug testing

I just accepted a position in Oregon subject to pre-employment drug testing and have a dilemma I'm hoping someone can help with.

I am medical marijuana patient from Montana and in a coule of days I need to submit to the urinalysis. I don't use any other drugs and cannibis only at night to help sleep/ptsd.

I am an honest person and am trying to decide if I should fake the test with synthetic or do what I think is right and call the testing /hiring company and ask them is thc is tested for hoping to submit a legit sample. This would more than likely make its way to the companies management of course.

Any thoughts on contacting the 3rd party hiring company and asking or just fake the test?