Code of Federal Regulations > Title 49 > Chapter A > Part 40 > Subpart G - Subpart G—Medical Review Officers and the Verification Process

U.S. Code of Federal Regulations

Regulations most recently checked for updates: Jan 21, 2026

§ 40.121 - Who is qualified to act as an MRO?

§ 40.123 - What are the MRO's responsibilities in the DOT drug testing program?

§ 40.125 - What relationship may an MRO have with a laboratory?

§ 40.127 - What are the MRO's functions in reviewing negative test results?

§ 40.129 - What are the MRO's functions in reviewing laboratory confirmed non-negative drug test results?

§ 40.131 - How does the MRO or DER notify an employee of the verification process after receiving laboratory confirmed non-negative drug test results?

§ 40.133 - Without interviewing the employee, under what circumstances may the MRO verify a test result as positive, or as a refusal to test because of adulteration or substitution, or as cancelled because the test was invalid?

§ 40.135 - What does the MRO tell the employee at the beginning of the verification interview?

§ 40.137 - On what basis does the MRO verify test results involving marijuana, cocaine, amphetamines, semi-synthetic opioids, or PCP?

§ 40.139 - On what basis does the MRO verify test results involving 6-acetylmorphine, codeine, and morphine?

§ 40.141 - How does the MRO obtain information for the verification decision?

§ 40.143 - [Reserved]

§ 40.145 - On what basis does the MRO verify test results involving adulteration or substitution?

§ 40.147 - [Reserved]

§ 40.149 - May the MRO change a verified drug test result?

§ 40.151 - What are MROs prohibited from doing as part of the verification process?

§ 40.153 - How does the MRO notify employees of their right to a test of the split specimen?

§ 40.155 - What does the MRO do when a negative or positive test result is also dilute?

§ 40.157 - [Reserved]

§ 40.159 - What does the MRO do when a drug test result is invalid?

§ 40.160 - What does the MRO do when a valid test result cannot be produced and a negative result is required?

§ 40.161 - What does the MRO do when a drug test specimen is rejected for testing?

§ 40.162 - What must MROs do with multiple verified results for the same testing event?

§ 40.163 - How does the MRO report drug test results?

§ 40.165 - To whom does the MRO transmit reports of drug test results?

§ 40.167 - How are MRO reports of drug results transmitted to the employer?