Dilute urine specimen

Scope

This regulation applies to drivers who produce a dilute urine specimen during a DOT drug test.

Regulatory citations

• 49 CFR 40.3 — What do the terms used in this part mean?
• 49 CFR 40.88 — What criteria do laboratories use to establish that a urine specimen is dilute or substituted?

Key definitions

• Dilute specimen: According to 49 CFR 40.3, a dilute urine specimen is one with creatinine and specific gravity values outside of the scope for human urine. Creatinine originates in the human body as creatine, which is found in muscle tissue and blood and normally excreted at a consistent rate in the urine as metabolic waste. A specimen is deemed dilute if:
  • The creatinine concentration is greater than or equal to 2 mg/dL but less than 20 mg/dL; and
  • The specific gravity of the urine is greater than 1.0010 but less than 1.0030 on a single aliquot.

Summary of requirements

Potential causes of dilute specimens. Certain drugs can sometimes cause abnormal creatinine levels. Another explanation for a dilute specimen may be an employee drinking excessive amounts of water prior to a drug screen.

Results. A dilute specimen is reported out as either:

• Negative-dilute.Numerical values for creatinine and specific gravity are listed.
• Positive-dilute. Drug(s)/metabolites are noted.

In the event a positive drug test is also dilute, the test is treated as a verified positive test. No further action is taken by the employer.

Action taken by the employer on a negative dilute depends upon the value of the creatinine.

Negative dilutes. If the creatinine level is equal to or greater than 2 mg/dL, but less than or equal to 5 mg/dL, the Medical Review Officer (MRO) will direct the employer to send the driver immediately for a recollection under direct observations. The result of the recollection becomes the test of record. If the driver refuses, it is a refusal to be tested, which is a DOT violation requiring the DOT return-to-duty process.

If the creatinine level is greater than 5 mg/dL, company policy would dictate a motor carrier’s actions. A motor carrier may send the driver for a retest. However, it cannot be under direct observation and must be a part of their DOT drug and alcohol testing policy. This policy must contain which test type(s) requires recollections, and as with any policy, the driver must be told in advance of testing what the motor carrier has decided about the matter. All employees must be treated the same based on this policy. Even though this is an optional policy, it still must be conducted on a DOT chain of custody and drivers must be given minimum advance notice that they must go to the collection site. If a driver refuses, it is a DOT drug violation requiring the DOT return-to-duty process. The result of this second test becomes the test of record.

If the result of a retest, MRO-directed or company policy, is a negative dilute with a creatinine level greater than 5 mg/dL, no additional testing is permitted. However, if the employer recollection yields a result that requires a direct observation test in accordance with 40.197(b)(1), and the MRO instructs yet another test, you must do so.