Short Answer

An adulterated specimen is a specimen that has been altered, shown either by the presence of a substance that is not normally found in human urine, or by an abnormal concentration of a substance that does occur naturally in urine. Under 49 CFR § 40.191, a verified adulterated result is treated as a refusal to test, carrying the same consequences as a verified positive drug test.

What Makes a Specimen Adulterated

Under 49 CFR § 40.3, adulteration is identified through laboratory analysis, either through detecting a substance that should not be present in normal human urine, or through finding an abnormal concentration of a substance that is naturally present. This is a chemical determination made by the laboratory, not a subjective judgment call.

Adulteration Is Treated as a Refusal to Test

49 CFR § 40.191 provides that a verified adulterated or substituted result is treated as a refusal to test. It also lists an employee's admission of adulterating or substituting a specimen as, on its own, a form of refusal. In either case, the consequence is the same as a verified positive drug test: it counts as a DOT violation under 49 CFR § 40.285(b), triggering the requirement for a SAP evaluation before the employee may resume safety-sensitive duties.

Adulterated vs. Substituted vs. Dilute

These three categories are often mentioned together but mean different things. An adulterated specimen has been chemically altered by an added substance or an abnormal concentration of an existing substance. A substituted specimen is one whose creatinine and specific gravity values are so diminished or divergent that the specimen is not consistent with human urine at all. A dilute specimen simply has creatinine and specific gravity values lower than expected for normal urine, without necessarily indicating tampering. Adulterated and substituted results are both treated as refusals under 40.191; a dilute result is handled differently, based on specific thresholds set elsewhere in Part 40.

Split Specimen Testing After an Adulterated Result

If the primary specimen is verified adulterated, the employee generally has the right to have the split specimen tested to confirm or challenge that finding. If the split specimen fails to reconfirm the primary result under the conditions set out in 49 CFR § 40.201, or if the split specimen is invalid or unavailable for testing, the test is cancelled instead of standing as a verified adulterated result.

Applicable Regulations

• 49 CFR § 40.3 defines an adulterated specimen.
• 49 CFR § 40.191 treats a verified adulterated result, and an admission of adulteration, as a refusal to test.
• 49 CFR § 40.201 addresses cancellation when split specimen testing fails to reconfirm the primary result or the split specimen is unavailable or invalid.

Professional Observation

In my experience, employees sometimes assume adulteration only means something was physically added to a cup in an obvious way. In reality, laboratory chemistry can detect abnormal concentrations of substances that occur naturally in urine, which is a more subtle finding than most people expect.

Common Misconceptions

Misconception

Adulterated and dilute specimens mean essentially the same thing.

Reality

A dilute specimen reflects naturally lower creatinine and specific gravity values, without necessarily indicating interference. An adulterated specimen reflects a substance that should not be present, or an abnormal concentration of one that should be, and is treated as a refusal to test.

Why the Confusion Occurs

Both terms describe urine that does not test as ordinary human urine, which makes them easy to conflate without understanding the different laboratory findings behind each one.

Frequently Asked Questions

Can an adulterated result be challenged?

The employee generally has the right to request split specimen testing. If the split fails to reconfirm the primary result, or is invalid or unavailable, the test is cancelled under 49 CFR § 40.201.

Does an adulterated result carry the same consequences as a positive drug test?

Yes. Under 49 CFR § 40.285(b), a verified adulterated result is treated as a DOT violation, the same as a verified positive result.

Related Articles

• What Is a Dilute Specimen?
• What Is a Refusal to Test?
• How Laboratory Testing Works

Primary Authorities/Sources

• 49 CFR § 40.3, Definitions
• 49 CFR § 40.191, Refusal to test
• 49 CFR § 40.201, Problems that always cancel a test

Facing an Adulterated Result Finding?

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