Instant drug tests are screening tools. They use antibodies that react to a target substance, and occasionally a different compound with a similar structure can trigger a preliminary positive. That is why every preliminary positive should be confirmed by a laboratory.
Reported causes of false positives
These are examples reported in medical literature. Not every test reacts to them, and results depend on the dose and the specific test.
| Panel | Substances reported to cause a false positive |
|---|---|
| AMP / MET | Decongestants such as pseudoephedrine, bupropion, trazodone, labetalol, selegiline |
| BZO | Sertraline, efavirenz |
| THC | Efavirenz; occasionally high doses of NSAIDs such as ibuprofen on some tests |
| PCP | Dextromethorphan, diphenhydramine, venlafaxine |
| MTD | Quetiapine, diphenhydramine |
| OPI | Poppy seeds, some quinolone antibiotics, rifampin |
Some "false positives" are actually true positives from an unexpected source: poppy seeds can contain the real substance the OPI panel detects, and CBD products can contain THC. See does CBD show up on a drug test.
Other reasons a result can be wrong
- Reading the test after 10 minutes, when lines can change
- Misreading a faint line (any visible T line is negative). See how to read a drug test cup.
- Expired or improperly stored tests
How to handle a preliminary positive
- Ask the person about prescriptions, over-the-counter medications and supplements.
- Do not take final action based on an instant test alone.
- Send the sample to a laboratory for confirmation (GC/MS or LC-MS/MS), which identifies the exact substance.
- Have results involving prescriptions reviewed by a qualified professional, such as a medical review officer.
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Request a Bulk QuoteFrequently asked questions
Can over-the-counter medicine cause a positive drug test?
Yes, occasionally. Some decongestants and sleep aids have been reported to trigger certain panels. A lab test can confirm.
Can poppy seeds cause a positive drug test?
They can trigger the OPI panel, because poppy seeds can contain the substance that panel detects.
How do you prove a false positive?
Request a laboratory confirmation test, which identifies the exact substance present.
How common are false positives?
They are uncommon with quality tests, but they do happen, which is why confirmation testing is standard practice.
Related guides
Instant urine tests give preliminary results. Confirm any preliminary positive with a laboratory test (such as GC/MS) before taking action. Always follow the package insert.