A positive drug test doesn’t automatically mean you’re fired or in legal trouble. What happens next depends on several factors: whether the test is for a federally regulated job, your employer’s specific drug policy, and whether you have a legitimate medical explanation for the result. In most cases, a lab-confirmed positive triggers a verification process before anyone at your workplace is even notified.
The Result Goes to a Doctor First
Before your employer learns anything, your positive result is sent to a Medical Review Officer, or MRO. This is a licensed physician whose job is to review the lab findings and determine whether there’s a medical explanation. The MRO checks the paperwork for errors, confirms the lab scientist signed off, and then contacts you directly for a confidential interview.
During this interview, the MRO explains that your test came back positive and gives you a chance to provide a legitimate reason. If you have a valid prescription for a medication that caused the result, this is where you present it. You carry the burden of proof, but the MRO cannot second-guess your prescribing doctor. If they believe you can produce documentation, they may give you up to five additional days to provide it. A confirmed prescription can result in the test being reported as negative.
The MRO or their staff will make at least three attempts to reach you over a 24-hour period using the phone numbers on your test form. If you decline to speak with the MRO, the result is verified as positive. If neither the MRO nor your employer can reach you within ten days, the same thing happens. Ignoring those calls works against you.
Why a Positive Might Not Be Accurate
Initial drug screening uses a technology called immunoassay, which works by detecting chemical structures that resemble specific drugs. The problem is that many common medications share structural similarities with controlled substances. At least 19 widely used prescription and over-the-counter medications have been documented to cause false positives, including ibuprofen, naproxen, certain antihistamines like diphenhydramine, the antidepressants bupropion, sertraline, trazodone, and venlafaxine, the heartburn medication ranitidine, and even some nasal decongestant inhalers. False positives for amphetamine and methamphetamine are the most frequently reported, but false flags for opioids, PCP, barbiturates, marijuana, and benzodiazepines also occur.
This is exactly why any initial positive gets sent to a second, more advanced test. Confirmatory testing uses mass spectrometry, a technique that identifies substances by their exact molecular weight rather than just their general chemical shape. This technology can distinguish between, say, an over-the-counter cold medicine and actual methamphetamine with extremely high accuracy. If the confirmatory test doesn’t find the specific drug above the required threshold, the result is reported as negative.
What the Cutoff Levels Mean
Drug tests aren’t simply “detected” or “not detected.” They use specific concentration thresholds, and your sample must exceed those thresholds to count as positive. For federal workplace testing using urine, the initial screening cutoff for marijuana is 50 nanograms per milliliter, and the confirmatory cutoff is 15 ng/mL. Cocaine’s initial cutoff is 150 ng/mL (confirmatory: 100 ng/mL). Amphetamines are screened at 500 ng/mL and confirmed at 250 ng/mL. Fentanyl has the lowest threshold at just 1 ng/mL for both initial and confirmatory testing.
Oral fluid (saliva) tests use much lower cutoffs across the board. Marijuana’s initial threshold drops to 4 ng/mL, cocaine to 15 ng/mL, and amphetamines to 50 ng/mL. This matters because if your employer uses oral fluid testing, smaller amounts of a substance can trigger a positive.
These numbers are set by the Department of Health and Human Services for federal workplace programs. Private employers may use different cutoff levels, though many follow the federal standard.
You Can Request a Retest
When you provide a urine sample for a drug test, it’s typically split into two specimens at the collection site. If the MRO notifies you of a verified positive, you have 72 hours from the moment of notification to request that the second specimen (the “split sample”) be tested at a different laboratory. This request can be verbal or written.
If you miss the 72-hour window, you may still be able to request the retest by showing that serious illness, injury, lack of actual notice, or inability to reach the MRO prevented you from asking in time. For federally regulated testing, your employer is generally required to cover the cost of the split specimen test, though some private employers may require you to pay upfront and reimburse you if the retest comes back negative.
What Happens at Work
Once the MRO verifies the result as positive, it goes to your employer’s Designated Employer Representative. What happens from there depends entirely on the type of job you hold and your employer’s policy.
Federally Regulated (Safety-Sensitive) Jobs
If you work in transportation, aviation, rail, pipeline operations, or another safety-sensitive role regulated by the Department of Transportation, the consequences follow a specific federal framework. You are immediately removed from safety-sensitive duties. You must then be evaluated by a Substance Abuse Professional (SAP), who is a licensed counselor or clinician trained in DOT regulations. The SAP determines what treatment or education you need, and you must complete the full program they prescribe.
After completing treatment, you need to pass a return-to-duty drug test with a verified negative result before you can resume safety-sensitive work. Even then, you’ll be placed on a follow-up testing schedule with unannounced tests for a set period. Your employer is not required to give you your job back, but if they do (or if a new employer hires you for a safety-sensitive role), the SAP evaluation, treatment, return-to-duty test, and follow-up testing are mandatory.
Private Employers
Outside of federally regulated industries, employer responses vary widely. Some companies have zero-tolerance policies that treat a confirmed positive as grounds for immediate termination. Others, particularly larger organizations, offer a second chance through an Employee Assistance Program, which typically involves counseling, treatment referral, and a follow-up testing period. A first offense in these workplaces might result in suspension rather than termination, with reinstatement contingent on completing a rehabilitation program and passing subsequent tests.
State laws also influence what your employer can do. Some states require employers to follow specific procedures before taking action on a positive test, such as providing written notice, giving you a chance to explain the result, or offering rehabilitation for a first offense. Other states give employers broad discretion. The protections available to you depend heavily on where you work.
Pre-Employment vs. Current Employee Testing
The practical consequences also differ based on when the test was taken. A positive result on a pre-employment screening typically means the job offer is withdrawn. Most employers are not obligated to tell you why, and there is generally no appeal process beyond the MRO verification and split specimen retest already described.
If you’re a current employee, you may have more options. Many company drug policies distinguish between pre-employment, random, post-accident, and reasonable-suspicion testing, with different consequences for each. A positive random test might trigger a “last chance agreement” where you keep your job conditionally, while a positive post-accident test might carry harsher consequences because of liability concerns.
What Shows Up on Your Record
A positive drug test is not a criminal charge and does not appear on a criminal background check. However, in federally regulated industries, positive results are recorded in a clearinghouse database. The FMCSA Drug and Alcohol Clearinghouse, for example, tracks violations for commercial motor vehicle drivers, and future employers conducting safety-sensitive hiring can see unresolved violations. The record remains until you complete the full return-to-duty process, including SAP evaluation, treatment, and follow-up testing.
For private-sector jobs, positive test results are generally kept in your personnel or medical file with that specific employer. There is no universal database that private employers share, but some industries use third-party background screening services that may include drug test history if you’ve signed a consent form allowing it.