• DOT · Federal
  • Employer policy
  • Urine
  • Lab confirmation

Reasonable Suspicion Drug Testing: What It Requires

Short answer

A trained supervisor's specific, contemporaneous observations of your appearance, behaviour, speech or body odour. It has to be based on what someone actually observed at the time — not a rumour, not a hunch, not a pattern of lateness, and not something reported second-hand. In DOT programmes the supervisor must have completed required training before they can make that determination.

Last verified 17 Aug 2026 Reviewed with Dr. Matthew Nuesse, DOT Certified Medical Examiner

What matters most

  • The determination must rest on specific, contemporaneous observations.
  • In DOT programmes the deciding supervisor must have completed required training.
  • Appearance, behaviour, speech and body odour are the observable categories.
  • Rumour, anonymous tips and general performance concerns are not sufficient on their own.
  • The observations should be documented at the time, not reconstructed later.

The standard is narrower than it sounds

Federal (DOT): Reasonable suspicion testing rests on specific, contemporaneous, articulable observations concerning your appearance, behaviour, speech or body odour Source 1DOT ODAPC49 CFR Part 40 — section navigator and Q&As — checked 17 Aug 2026Source 2eCFR49 CFR Part 40 — Procedures for Transportation Workplace Drug and Alcohol Testing Programs — checked 17 Aug 2026. Every word in that formula is doing work.

Specific means describable in concrete terms rather than a general impression. Contemporaneous means observed now, not last week. Articulable means the supervisor can state what they saw. And the categories are limited to things that can be observed directly.

What does not count

Federal (DOT): A rumour does not count. An anonymous tip does not count on its own. Neither does a pattern of lateness, declining performance, or a colleague's report of something the supervisor did not witness — those may justify a conversation, but they are not observations of your present condition Source 1DOT ODAPC49 CFR Part 40 — section navigator and Q&As — checked 17 Aug 2026Source 2eCFR49 CFR Part 40 — Procedures for Transportation Workplace Drug and Alcohol Testing Programs — checked 17 Aug 2026.

Federal (DOT): The determination also has to be made by a supervisor who has completed the required training. Someone untrained cannot substitute their judgement, however senior they are Source 1DOT ODAPC49 CFR Part 40 — section navigator and Q&As — checked 17 Aug 2026Source 2eCFR49 CFR Part 40 — Procedures for Transportation Workplace Drug and Alcohol Testing Programs — checked 17 Aug 2026.

If you are the employer

Employer policy: This is the testing category that generates the most disputes, and almost always for the same two reasons: the deciding supervisor was not trained, or the observations were written up afterwards in general terms.

Employer policy: Documenting at the time, in concrete language, is the whole defence. Slurred speech, unsteady gait, the specific smell noted at a specific time is a record. Seemed under the influence is not. SAMHSA's employer guidance covers building this into a policy properly Source 3SAMHSADrug-Free Workplace Programs — checked 17 Aug 2026Source 4SAMHSAWorkplace Drug Testing Resources — checked 17 Aug 2026.

If you are the employee

You can ask what was observed, and who made the determination. Those are reasonable questions and the answers are supposed to exist. Refusing the test, though, is not the way to contest it — a refusal is treated as seriously as a positive result, so the sequence is to comply now and raise the process afterwards.

Federal (DOT): The collection itself is identical to any other test, with the same confirmation and physician review before anything reaches your employer Source 1DOT ODAPC49 CFR Part 40 — section navigator and Q&As — checked 17 Aug 2026Source 2eCFR49 CFR Part 40 — Procedures for Transportation Workplace Drug and Alcohol Testing Programs — checked 17 Aug 2026.

A note on medical conditions

Several medical conditions produce signs that resemble the observable indicators — a diabetic episode, a neurological condition, a reaction to prescribed medication. This is worth knowing on both sides: for employers as a reason to describe rather than diagnose, and for employees as something to raise with the reviewing physician rather than the supervisor.

How the process runs

  1. Observation

    A trained supervisor observes specific indicators in your appearance, behaviour, speech or body odour.

  2. Determination

    That supervisor — not a colleague, and not someone relaying a report — decides that reasonable suspicion exists.

  3. Documentation

    The observations are recorded promptly, while they are contemporaneous rather than remembered.

  4. Testing

    You are taken for testing, and the collection follows exactly the same procedure as any other test.

What this means for you

For employers: train the supervisors who will make these calls, and document observations at the time in concrete language. Those two habits prevent most disputes. For employees: comply with the test, then ask what was observed and by whom. Refusing is the one response that makes your position worse regardless of the merits. This is general information, not legal advice.

Rules differ by state and employer. This section describes federal requirements. Your state law or your employer’s written policy may add rules on top of them.

When the answer changes

Alcohol reasonable-suspicion testing has tighter timing expectations than drug testing, because alcohol concentration falls over time. Employers outside a federal programme set their own standard, which may be looser or stricter than the federal one — the written policy governs. And some states impose additional requirements on suspicion-based testing, so a state-law check is worth doing before relying on the federal standard alone.

Dr. Matthew Nuesse
Medical review

Dr. Matthew Nuesse

DOT Certified Medical Examiner

Dr. Matthew Nuesse is a DOT Certified Medical Examiner who reviews Exploro's drug testing guides for medical and procedural accuracy.

Common questions

No. A sample that screens positive goes on to a second, more specific confirmatory test, and the result is then reviewed by a Medical Review Officer. The MRO must give you the chance to explain a legitimate medical reason before reporting the result to your employer.

Source:49 CFR Part 40 (ODAPC), 49 CFR Part 40 (eCFR)

Not under the federal rules. 49 CFR Part 40 governs how you are tested and removed from safety-sensitive duties — it says nothing about your employment. Whether you keep your job depends on your employer's written policy and any collective agreement.

Source:49 CFR Part 40 (ODAPC), 49 CFR Part 40 (eCFR)

Yes. Every DOT collection splits your sample into two bottles. If the Medical Review Officer reports a positive, refusal, adulterated or substituted result, you have 72 hours from being told to request that the second bottle be tested at a different certified laboratory. The MRO has to tell you about this right.

Source:49 CFR Part 40 (ODAPC), 49 CFR Part 40 (eCFR)

Official sources

Every factual claim above is drawn from these sources. Each was opened and checked on the date shown. Where a rule differs between agencies, the source that governs is named in the text.

  1. DOT ODAPC · 49 CFR Part 40 (ODAPC)

    49 CFR Part 40 — section navigator and Q&As

    Checked 17 Aug 2026
    View official source ↗ (opens in a new tab)
  2. eCFR · 49 CFR Part 40 (eCFR)

    49 CFR Part 40 — Procedures for Transportation Workplace Drug and Alcohol Testing Programs

    Checked 17 Aug 2026
    View official source ↗ (opens in a new tab)
  3. SAMHSA · SAMHSA — Drug-Free Workplace

    Drug-Free Workplace Programs

    Checked 17 Aug 2026
    View official source ↗ (opens in a new tab)
  4. SAMHSA · SAMHSA — Drug testing resources

    Workplace Drug Testing Resources

    Checked 17 Aug 2026
    View official source ↗ (opens in a new tab)