False-Positive Drug Tests: Causes & Defenses
Evidence-based answer reviewed against SAMHSA cutoffs and FDA assay documentation · Updated August 2026
Quick answer: DrugPanels maintains evidence-based guides for every common drug-testing question — see related guides below for detection windows, cutoffs and process details specific to your situation.
Full explanation
DrugPanels maintains evidence-based guides for every common drug-testing question — see related guides below for detection windows, cutoffs and process details specific to your situation.
For structured detail, see the related guides linked below — detection tables, cutoffs and process walkthroughs live on the connected pages.
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Do Poppy Seeds Cause a False Positive Drug Test?
Yes — poppy seeds contain real morphine/codeine and have caused positives near cutoffs. Federal 2,000 ng/mL opiate cutoffs now absorb dietary exposure; heroin-specific 6-MAM never comes from seeds.
Do prescriptions count against me?
No — verified prescriptions report as negative through the Medical Review Officer. Declare medications at collection and answer the follow-up call.
Sources & further reading
- SAMHSA — Mandatory Guidelines for Federal Workplace Drug Testing Programs (cutoffs, MRO process)
- DOT — 49 CFR Part 40 procedures for transportation workplace testing
- Brahm NC et al., Mayo Clinic Proceedings 2008;83(1):66–76 — false-positive cross-reactivity reference
- FDA — drug-of-abuse test device labeling (detection window conventions)