Every DOT drug test result goes through a certified MRO before it reaches the employer. Use the directories below to find a qualified MRO for your program.
A Medical Review Officer (MRO) is a licensed physician who receives and reviews laboratory results for DOT federally mandated drug tests. The MRO is a required part of every DOT drug testing program — results cannot be reported directly to an employer without MRO review.
The MRO receives the chain-of-custody form and laboratory result, then reviews each result for medical accuracy and legitimacy before reporting it to the employer.
For non-negative results, the MRO contacts the employee directly to ask whether there is a legitimate medical explanation — such as a valid prescription — for the result.
The MRO determines whether the final result is negative, positive or cancelled, and reports it to the employer or C/TPA. Be careful with refusals: the MRO does not determine every refusal. The MRO makes the refusal determinations assigned to it — an adulterated or substituted specimen, and a failure to provide a sufficient specimen where the required medical evaluation found no adequate medical explanation (§40.193(d)(2)), or a failure to undergo a medical evaluation the MRO directed. Conduct-based refusals belong to the employer — failing to appear, leaving before the process is complete, refusing to be observed and similar are decided by the employer under §40.191 and §40.355(i). One exception: where a C/TPA notified an owner‑operator or other individual employee to report for a test (other than pre‑employment) and they did not appear, the C/TPA makes that determination (§40.61(a)).
The MRO protects employees from false positives while protecting the integrity of the testing program — a legally required safeguard in federal workplace drug testing.
Under 49 CFR Part 40, every DOT-regulated employer must designate an MRO for their drug testing program. This includes employers in:
Under 49 CFR §40.121, an MRO must be a licensed physician (M.D. or D.O.) who has completed training in federal drug testing regulations and passed a qualifying examination administered by a nationally recognized MRO certification board. The two primary certifying organizations are:
Both organizations maintain searchable directories of certified MROs. Use either to find a qualified MRO for your employer or testing program.
The MROCC is one of the primary meeting the §40.121 examination requirement through a nationally recognized MRO certification or subspecialty board (Part 40 sets the standard; it does not endorse particular organisations) MRO certifying bodies. Their directory allows employers, C/TPAs, and collectors to search for CMRO-certified physicians by location. MROCC also sets standards for MRO training and examination under 49 CFR Part 40.
Visit MROCC Directory →AAMRO is the largest professional association for MROs in the United States. Their searchable directory lists AAMRO-certified MROs nationwide. AAMRO also provides MRO training courses and publishes guidance on DOT drug testing regulations and MRO responsibilities.
Visit AAMRO Directory →TestRight Academy trains and qualifies DOT urine collectors and Breath Alcohol Technicians (BATs) through live virtual qualification programs — fully compliant with 49 CFR Part 40.
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