How Does an MRO Evaluate a Medical Condition after an Insufficient DOT Specimen?

When a collector reports an insufficient specimen, 49 CFR 40.193(c) requires a medical evaluation within five days by a licensed physician acceptable to the MRO, who may perform it if the MRO has appropriate expertise. When another physician performs it, the MRO explains that the employee was required to take a DOT drug test but could not provide a sufficient specimen, and explains the consequences of refusing a required test.

The referral physician recommends a determination to the MRO, who "must seriously consider and assess" it and reports the determination to the DER in writing. If a medical condition has, or with a high degree of probability could have, precluded a sufficient specimen, the MRO cancels the test. If there is not an adequate basis for that finding, the MRO marks a refusal to test. Under 40.193(e), a medical condition includes an ascertainable physiological condition, such as a urinary system dysfunction, or a medically documented pre-existing psychological disorder, but does not include unsupported assertions of "situational anxiety" or dehydration.

Under 49 CFR 40.195, a permanent or long-term condition in a pre-employment, return-to-duty or follow-up test leads the MRO to determine, through a medical evaluation, whether there is clinical evidence of illicit drug use. Without such evidence, the MRO reports a negative test with written notations. With it, the MRO reports a cancelled test, which does not serve as a negative test for allowing the employee to begin or resume safety-sensitive functions. Acute or temporary conditions, such as cystitis, urethritis or prostatitis, do not receive this consideration.

In a notice published October 1, 2026 (91 FR 62409, docket DOT-OST-2026-3664), DOT requested public comment on a petition asking it to amend Part 40 provisions on invalid specimen determinations, including documented review of medically supported functional voiding disorders before refusal determinations based on inability to provide a specimen under direct observation. The notice does not change Part 40.

The collection steps are covered in What Happens When an Employee Cannot Provide Enough Urine for a DOT Test?, and refusals in What Counts as Refusing a DOT Drug Test?.

Medical Review Officers have their own category in the MyDrugTesting.com directory, separate from collection sites.