How Long Does Hydroxyzine Stay in Blood?
Evidence-based answer reviewed against SAMHSA cutoffs and FDA assay documentation · Updated August 2026
Quick answer: Most people clear Hydroxyzine from blood within n/a of last use — heavy or daily use stretches that window substantially. Not screened; TCA-strip cross-reactivity risk.
Hydroxyzine detection windows by test type
Each specimen tells a different story because each samples different biology:
| Test type | Typical Hydroxyzine detection window |
|---|---|
| Urine | any: interference ~1–3 days post-dose |
| Saliva (Mouth Swab) | any: n/a |
| Hair Follicles | n/a |
| Blood | any: n/a |
('Blood testing measures ACTIVE circulation — closest proxy to impairment, shortest windows (hours-to-a-couple-days). Hospitals order it clinically; courts order it post-accident (DUI contexts); employers rarely bother given logistics and cost.',)
Why detection works this way
Hydroxyzine is never a target analyte. Structurally antihistamine-TCA adjacent, it can flag tricyclic screens (like diphenhydramine). Confirmations close the loop.
Testing cutoffs in plain language
Not screened; TCA-strip cross-reactivity risk. A specimen under the initial cutoff reports negative without further work; a screen above cutoff gets confirmed by mass spectrometry before anyone sees a positive.
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Do prescriptions count against me?
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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)