An adulterated result on a drug test means the laboratory found that something was added to the urine sample to interfere with testing. Specifically, it means the specimen contains a substance that doesn’t belong in normal urine, or contains a naturally occurring substance at a concentration far outside the normal range. Under federal workplace testing rules, an adulterated result is treated as a refusal to test, which carries serious consequences.
What the Lab Actually Detected
Laboratories don’t just test urine for drugs. They also run what’s called specimen validity testing, which checks whether the sample is genuinely unaltered human urine. This involves measuring three core properties: pH (acidity), creatinine concentration, and specific gravity (how dense the liquid is compared to water). Some labs also test for oxidizing agents, which are chemicals that can break down drug molecules before the test can detect them.
Normal urine has a pH that falls within a predictable range, a creatinine level at or above 20 mg/dL, and a specific gravity between roughly 1.0020 and 1.0200. When pH swings to an extreme, or when the lab identifies a chemical that has no business being in a urine sample, the result is flagged as adulterated. Common adulterants include bleach, vinegar, eye drops, and commercial products marketed as “detox” additives. These substances work by either destroying drug molecules in the sample or by disrupting the chemical reactions the lab uses to detect them.
How Adulterated Differs From Dilute or Substituted
Drug test results can come back with several non-standard findings, and they don’t all mean the same thing. Understanding the differences matters because the consequences vary significantly.
- Dilute: The urine has lower-than-expected creatinine (between 2 and 20 mg/dL) and low specific gravity. This can happen from drinking large amounts of water before the test. A dilute positive is still treated as a positive. A dilute negative may require a retest, depending on the employer.
- Substituted: The creatinine is below 2 mg/dL and the specific gravity falls outside the range consistent with human urine. This suggests the sample isn’t real urine at all, possibly replaced with water, synthetic urine, or another liquid.
- Adulterated: A foreign substance was added to the sample, or a normal substance appears at an abnormal concentration. This points to deliberate chemical tampering.
- Invalid: The lab got abnormal results but can’t definitively classify the sample as adulterated or substituted. A pH between 9.0 and 9.5, for example, might fall into this category if there’s a plausible medical explanation.
The key distinction is intent. A dilute specimen could be accidental. An adulterated specimen, by definition, contains something that shouldn’t be there, and labs treat it as evidence of tampering.
Why It’s Treated as a Refusal to Test
Under Department of Transportation regulations and most federal workplace drug testing programs, a verified adulterated result is legally equivalent to refusing a drug test. The same applies to a substituted result. This isn’t a technicality. Federal rules state explicitly: “if the MRO reports that you have a verified adulterated or substituted test result, you have refused to take a drug test.”
A refusal carries the same penalties as a positive test, and in many cases worse. For DOT-regulated employees (truck drivers, pilots, transit workers, pipeline operators), this means immediate removal from safety-sensitive duties, a mandatory evaluation by a substance abuse professional, and a return-to-duty process before resuming work. For non-DOT employers, the consequences depend on company policy, but termination is common. Notably, federal regulations specify that the consequences of a refusal “cannot be overturned or set aside by an arbitration, grievance, State court or other non-Federal forum.”
What Happens After an Adulterated Result
Before the result becomes final, a Medical Review Officer (MRO) reviews it. The MRO is a licensed physician who contacts you to ask whether there’s a legitimate medical explanation for the abnormal findings. Certain medications, medical conditions, or dietary factors can, in rare cases, push urine chemistry outside normal ranges. If you can provide a verified medical explanation, the MRO may reclassify the result.
If no medical explanation exists, the MRO verifies the result as adulterated, and it’s reported to the employer as a refusal to test. At that point, the process mirrors what would happen after a positive result, or in some workplaces, triggers an even stricter response. Simply admitting to an MRO or collector that you tampered with the specimen also counts as a refusal under federal rules, even if the lab hasn’t flagged anything yet.
Can You Challenge an Adulterated Result?
You do have options, though they’re limited. When the MRO contacts you, that conversation is your primary opportunity to present a medical explanation. If you believe the lab made an error, you can request that the split specimen (a second portion of your original sample, collected at the same time) be tested at a different certified laboratory. If the second lab doesn’t confirm the adulterated finding, the result is typically canceled.
The split specimen retest is your strongest safeguard against a lab mistake. However, if both labs agree the sample was adulterated, the finding stands. At that point, challenging the result through legal channels is difficult, particularly in federally regulated industries where the rules explicitly limit the ability of outside courts or arbitrators to reverse the outcome.