The following is summarized from DOT Rule 49 CFR Part 40 Section 40.191
As an employee, you have refused to take a drug or alcohol test if you:
Fail to appear for any test (except a pre-employment test) within a reasonable time, as determined by the employer after being directed to do so by the employer. This includes the failure of an employee (including an owner-operator) to appear for a test when called by a C/TPA.
Fail to remain at the testing site until the testing process is complete. Exception is if it’s a pre-employment test and you leave before the process begins.
Fail to provide a urine specimen for any drug test or fail to provide a sufficient amount of urine, and there is no adequate medical explanation for the failure.
Fail or decline to take any drug test the employer or collector has directed you to take.
Fail to cooperate with any part of the testing process (e.g., refuse to empty pockets when directed by the collector, behave in a confrontational way that disrupts the collection process, fail to wash hands after being directed to do so by the collector).
For an observed collection, fail to follow the observer’s instructions to raise your clothing above the waist, lower clothing and underpants, and to turn around to permit the observer to determine if you have any type of prosthetic or other device that could be used to interfere with the collection process.
Possess or wear a prosthetic or other device that could be used to interfere with the collection process.
Admit to the collector or MRO that you adulterated or substituted the specimen.
A Refusal To Test has the same consequences as a positive test result.