What to Say When a Medical Review Officer Calls

When a Medical Review Officer calls about a drug test, return the call within 72 hours and be ready to explain any positive or unusual result with specific, documented information about your prescriptions. That is the short version of what to say when a Medical Review Officer calls: get on the phone in time, name the medication and the prescribing doctor, and have proof you can send. Everything else follows from those two things.

Call Back Within 72 Hours

The MRO or their staff will first try to reach you directly, making at least three attempts over a 24-hour period using the phone numbers on your collection form. If those calls don’t connect, the MRO contacts your employer’s Designated Employer Representative, who reaches out and tells you to call the MRO immediately.¹

Once that employer contact happens, a strict 72-hour clock starts. Miss it and the MRO can verify the result as positive or as a refusal to test without ever interviewing you.²

There is one narrow safety valve. If you missed the window because of a serious illness, injury, or circumstances that genuinely made contact impossible, you can present documentation to the MRO within 60 days of the verification. If the MRO finds the reason legitimate, they can reopen the case and let you go through the interview. “I didn’t check my voicemail” won’t cut it. The regulation contemplates things like hospitalization or a disconnected phone.²

The practical rule: if you’ve taken a workplace drug test recently and an unfamiliar number is calling, pick up. If you get a voicemail from an MRO’s office, call back the same day.

What to Have in Front of You Before You Dial

The MRO will ask specific questions, and vague answers hurt you. Pull the following together before you return the call:

Prescription details: medication name, dosage, prescribing doctor’s name and phone number, the pharmacy that filled it, and the date the prescription was written or most recently filled.
Supporting documentation: prescription bottles with your name on the label, pharmacy printouts, or medical records showing the prescription is current and in your name.
Over-the-counter medications and supplements you’ve taken recently, including cold medicines, sleep aids, and herbal products.

You may not need to produce all of it on the call itself, but the MRO can ask for documentation afterward. Having it ready means you can respond quickly instead of scrambling while a deadline runs.

What to Say During the Interview

At the start of the call, the MRO must tell you three things: that the lab confirmed a non-negative result, which specific drug or drugs were detected (or the basis for an adulteration or substitution finding), and that their final decision will rest on the information you provide during this conversation.³

The MRO must also warn you, before asking about your medical history, that any information you share about medications or medical conditions affecting safety-sensitive duties can be disclosed to third parties without your consent if it raises a safety concern. Listen for that warning. It changes what you should volunteer.³

Then comes your turn. Be direct and specific: name the medication, the prescribing doctor, the condition it treats, and how long you’ve been taking it. Don’t volunteer unrelated medical history. Don’t argue that the test itself was unfair. The MRO is looking for one thing: a legitimate medical explanation supported by a valid prescription consistent with federal controlled substance law.⁴

You carry the burden of proof. The MRO isn’t going to hunt for explanations on your behalf. Present your evidence at the time of the interview. The MRO has discretion to give you up to five additional days if there’s a reasonable basis to believe you can produce relevant documentation in that window, but don’t count on it.⁴

One reassuring detail: if you have a legitimate prescription, the MRO is not allowed to second-guess your doctor’s decision to prescribe it. The question is whether the prescription exists and is valid, not whether it was medically appropriate.⁴

Explanations That Don’t Work

Certain explanations come up constantly in MRO interviews and get rejected every time. Don’t spend your one interview on any of these.

CBD Products

The Department of Transportation does not accept CBD use as a legitimate medical explanation for a positive THC result. It doesn’t matter that hemp-derived CBD is legal under the 2018 Farm Bill, that the product label said “THC-free,” or that you bought it at a licensed dispensary. If your test comes back positive for marijuana metabolites, the MRO cannot verify it as negative based on CBD use.⁵

Medical Marijuana

Even in states where marijuana is legal for medical or recreational use, the DOT treats it as an unacceptable substance for anyone in a safety-sensitive position. A state-issued medical marijuana card is not a valid prescription under federal controlled substance law. The regulation explicitly categorizes marijuana as a drug of abuse that “can never be the basis for a legitimate medical explanation.”⁴

Poppy Seeds

If your test shows morphine or codeine at or above 15,000 ng/mL in urine or 150 ng/mL in oral fluid, the regulations specifically say poppy seed consumption is not a legitimate medical explanation. Below those thresholds the MRO has more discretion, but at those concentrations the poppy seed defense is off the table by rule.⁶

If the Result Goes Against You: Ask for a Split Specimen Test

If the MRO verifies your result as positive or as a refusal to test because of adulteration or substitution, you have the right to request testing of the split specimen. This is the second portion of your original sample, sealed separately at collection. You have 72 hours from the time the MRO notifies you of the verified result to make the request, and it can be verbal or in writing.⁷

Miss the 72-hour window and you can still present documentation showing that serious illness, injury, lack of actual notice, or an inability to reach the MRO’s office prevented a timely request. If the MRO finds the reason legitimate, they must direct the split specimen test to proceed as if you had asked on time.⁷

Cost is a common worry, and the rules are employee-friendly. Your employer cannot make you pay upfront as a condition of the test happening. If you’re unwilling or unable to cover the cost, your employer must pay and ensure the retest happens on time. They can seek reimbursement from you later through company policy or a collective bargaining agreement, but they can’t hold the test hostage while you sort out payment.⁸

What Your Employer Actually Hears

After the interview, the MRO reports a final result to your employer: negative, positive, dilute, refusal to test, or cancelled. For a positive result, the report identifies which drug or drugs were involved. For a cancelled test, the MRO includes the reason.⁹

What the MRO does not report: the concentration of the substance in your sample, the details of your medical conditions, or the prescriptions you’re taking. If you produce a valid prescription and the MRO verifies the result as negative, your employer simply gets told “negative.” Quantitative test values are specifically prohibited from being shared with your employer.⁹

When a Valid Prescription Still Triggers a Safety Report

Most people don’t expect this part. Even with a perfectly valid prescription and a verified-negative result, the MRO may still send a separate safety report to your employer. This happens when the MRO determines, using reasonable medical judgment, that your continued performance of safety-sensitive duties could pose a significant safety risk, or that the information would make you medically unqualified under DOT regulations.¹⁰

Before that report goes out, the MRO must give you five business days for your prescribing physician to contact the MRO and discuss whether the medication can be changed to one that doesn’t create a safety issue. The five-day window starts from the date the MRO reports the verified negative result. If the safety concern remains after that conversation, or if five business days pass with no contact from your doctor, the MRO proceeds with the safety report.³

The safety report is a separate written communication, not part of the standard test result. It describes the specific nature of the concern, such as the effects of the medication or the underlying condition you disclosed. Your employer then decides what action, if any, to take. The MRO can recommend evaluation by an occupational medicine physician, but the employment decision belongs to your employer.¹⁰

The practical implication for the interview: when the MRO gives that early warning about safety-related disclosures, take it seriously. Answer the questions you’re asked. Don’t volunteer conditions or medications the MRO didn’t ask about.

One Boundary: DOT vs. Non-DOT Tests

Everything above applies to DOT-regulated drug testing, which covers safety-sensitive positions in industries like trucking, aviation, rail, transit, and pipeline work. The rules come from 49 CFR Part 40.

If your drug test was ordered by a private employer outside the DOT framework, the process may look similar on the surface, since many private employers voluntarily use MRO review. The specific timelines, split specimen rights, and stand-down protections described here are federal DOT requirements and may not apply to your situation. Non-DOT testing programs are governed by company policy, sometimes shaped by state law, and the MRO’s role and your rights can vary. If you’re not sure which type of test you took, ask your employer or the MRO’s office directly. That answer determines which rules protect you.