What Happens When a DOT Drug Test Result Is Dilute?

A dilute specimen is a urine specimen with creatinine and specific gravity values lower than expected for human urine (49 CFR 40.3). The laboratory reports it to the MRO, and the MRO reports it to the employer along with the verified result. Section 49 CFR 40.197 tells the employer what to do next, and the answer depends on whether the result was positive or negative and, for negatives, on the creatinine level.

Positive dilute. A dilute specimen that tests above the cutoff levels is still a verified positive, and the employer may not send the employee for another test because the specimen was dilute (49 CFR 40.197(a)).

Negative dilute with creatinine of 2 to 5 mg/dL. If the creatinine concentration was at least 2 mg/dL but no more than 5 mg/dL, the MRO directs a recollection under direct observation, and the employer must carry it out immediately (49 CFR 40.197(b)(1)). Direct observation procedures are covered in what is an observed collection.

Negative dilute with creatinine above 5 mg/dL. The employer may, but is not required to, direct the employee to take another test immediately (49 CFR 40.197(b)(2)). If it chooses to retest:

• The recollection is not directly observed, unless another basis for direct observation exists under 49 CFR 40.67(b) or (c).
• The employer treats employees the same, so it may not retest some employees and not others.
• It may set different policies for different test types, such as retesting pre-employment dilutes but not random dilutes.
• It informs employees of these decisions in advance.

Rules for any retest. For a retest under either paragraph, the following apply (49 CFR 40.197(c)):

• The employee gets the minimum possible advance notice to go to the collection site.
• The retest result, not the earlier one, is the result of record.
• If the retest is also negative and dilute, the employer may not require a third test because of dilution. The exception is when the MRO directs an observed recollection for a 2 to 5 mg/dL result.
• An employee who declines a directed retest has refused the test.

Policy choice. Because the over 5 mg/dL retest is optional, the employer decides in advance and tells employees. A carrier that retests pre-employment dilutes, for example, applies that choice to each applicant in the same way.