Short Answer

Every DOT-regulated urine drug test must be analyzed at a laboratory certified under HHS Mandatory Guidelines, a certification program overseen by SAMHSA. The laboratory receives the primary specimen, tests it, and reports the finding to a Medical Review Officer (MRO), never directly to the employer. A split specimen is kept in reserve in case the employee later disputes a non-negative result.

Why the Laboratory Must Be Certified

DOT requires the use of an HHS-certified laboratory for regulated drug testing. SAMHSA (the Substance Abuse and Mental Health Services Administration) certifies these laboratories under HHS Mandatory Guidelines, a certification framework that exists separately from, and is referenced by, 49 CFR Part 40. This background is general and administrative in nature rather than a specific Part 40 regulatory text, so readers who need the details of the certification process itself should look to SAMHSA's own published guidelines.

Primary and Split Specimens

At collection, the specimen is generally divided into two portions. The primary specimen, the "A" bottle, is the one the laboratory tests first. The split specimen, the "B" bottle, is retained rather than tested immediately. If the primary specimen comes back verified positive, adulterated, or substituted, the employee can request that the split specimen be tested at a second HHS-certified laboratory to confirm or challenge that finding.

What the Laboratory Actually Tests For

The laboratory analyzes the specimen for the drug classes covered under 49 CFR Part 40: marijuana, cocaine, amphetamines, phencyclidine (PCP), and opioids. Along the way, it also evaluates the specimen's basic characteristics, such as creatinine and specific gravity, which can reveal whether a specimen is dilute, substituted, or otherwise inconsistent with normal human urine.

Reporting Results: Laboratory to MRO, Not to the Employer

The laboratory reports its finding to the MRO. A negative result means no drug was detected, or the amount detected fell below the applicable cutoff, on a specimen that tested as valid. A non-negative specimen is one reported as adulterated, substituted, positive, or invalid. The employer never receives raw laboratory data directly; it receives the MRO's verified determination after MRO review is complete.

Applicable Regulations

• 49 CFR § 40.3 defines primary specimen, split specimen, non-negative specimen, and chain of custody.

Applicable Guidance

SAMHSA certifies the laboratories used for DOT-regulated drug testing under HHS Mandatory Guidelines. This is administrative guidance supporting the Part 40 testing program, not a Part 40 regulatory provision itself.

Professional Observation

In my experience, employees sometimes picture the laboratory as the decision maker in their case. It helps to remember that the lab's role is limited to producing an accurate scientific result. The decision about what that result means for the employee's DOT status belongs to the MRO, not the laboratory.

Common Misconceptions

Misconception

An employer can choose any laboratory it wants for DOT drug testing.

Reality

DOT rules require use of a laboratory certified under HHS Mandatory Guidelines. An employer cannot substitute a non-certified lab for DOT-regulated testing.

Why the Confusion Occurs

Employers may use non-certified labs for other, non-DOT workplace testing programs, which can blur the distinction for someone unfamiliar with the DOT-specific requirement.

Frequently Asked Questions

Can I request which laboratory tests my split specimen?

The split specimen must go to a second HHS-certified laboratory, but the specific facility is arranged through the testing process rather than chosen by the employee directly.

Does the laboratory know my job or employer?

The laboratory works from the CCF and specimen identifiers required for chain of custody. Detailed questions about what information a specific lab receives should be directed to the collection site or C/TPA involved in a given case.

Related Articles

• DOT Drug Testing Process
• What Is a Dilute Specimen?
• What Is an Adulterated Specimen?

Primary Authorities/Sources

• 49 CFR § 40.3, Definitions

Questions About a Laboratory Result?

If you have questions about how your specimen was handled or tested, the MRO assigned to your case is the right first point of contact.

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