What does a Medical Review Officer (MRO) do?

An MRO is a licensed physician who reviews and verifies laboratory drug test results. Under 49 CFR Part 40, the MRO contacts the donor to discuss any non-negative result, evaluates legitimate medical explanations such as a valid prescription, and makes the final determination to report the result as positive, negative, or cancelled. The MRO acts as an independent gatekeeper to protect the accuracy and fairness of the process.

Why did an MRO call me about my drug test?

The MRO contacts a donor when the laboratory reports a non-negative result. This verification interview gives you the opportunity to disclose legitimate medical explanations — such as a valid prescription — before the result is finalized. Responding promptly is important, because an MRO who cannot reach the donor may still verify the result based on lab data.

Is an MRO required for all drug tests?

An MRO review is required for all DOT-regulated drug testing. Many employers also use an MRO for non-DOT programs as a best practice to ensure results are medically verified and defensible, though it is not federally mandated outside DOT testing.

MRO — Medical Review Officer in Drug Testing | Glossary

Medical Terms & Procedures ← Back to Glossary

MRO (Medical Review Officer)

A licensed physician responsible for receiving and interpreting laboratory drug test results in a workplace drug testing program.

Key Facts

Must be a licensed physician with specialized MRO training
Reviews all laboratory-positive drug test results
Conducts verification interviews with donors
Can request reanalysis of the split specimen
Required for all DOT drug testing programs

A Medical Review Officer (MRO) is a licensed physician with knowledge of substance abuse disorders and DOT drug testing regulations. Under 49 CFR Part 40, the MRO verifies test results, contacts the donor to discuss positive results (the "verification" interview), evaluates legitimate medical explanations (such as valid prescriptions), and makes the final determination to report a result as positive, negative, or cancelled. The MRO serves as a gatekeeper to protect the accuracy and fairness of the drug testing process.

Frequently Asked Questions

What does a Medical Review Officer (MRO) do?: An MRO is a licensed physician who reviews and verifies laboratory drug test results. Under 49 CFR Part 40, the MRO contacts the donor to discuss any non-negative result, evaluates legitimate medical explanations such as a valid prescription, and makes the final determination to report the result as positive, negative, or cancelled. The MRO acts as an independent gatekeeper to protect the accuracy and fairness of the process.
Why did an MRO call me about my drug test?: The MRO contacts a donor when the laboratory reports a non-negative result. This verification interview gives you the opportunity to disclose legitimate medical explanations — such as a valid prescription — before the result is finalized. Responding promptly is important, because an MRO who cannot reach the donor may still verify the result based on lab data.
Is an MRO required for all drug tests?: An MRO review is required for all DOT-regulated drug testing. Many employers also use an MRO for non-DOT programs as a best practice to ensure results are medically verified and defensible, though it is not federally mandated outside DOT testing.

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States Covered

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