Does Naltrexone Show Up on Urine test?

Evidence-based answer reviewed against SAMHSA cutoffs and FDA assay documentation · Updated August 2026

Quick answer: On a urine test, Naltrexone typically registers for 1–3 days (oral); injectable releases for weeks after last use. ('Urine remains the employment default because it balances cost, window-length and legal defensibility. Metabolite CONCENTRATIONS (not presence/absence) decide results against cutoff tables, which is why hydration status moves numbers and why validity checks (creatinine, specific gravity) police dilution attempts.',)

How urine testing catches Naltrexone

('Urine remains the employment default because it balances cost, window-length and legal defensibility. Metabolite CONCENTRATIONS (not presence/absence) decide results against cutoff tables, which is why hydration status moves numbers and why validity checks (creatinine, specific gravity) police dilution attempts.',)

Never screened on standard panels; specialized adherence monitoring exists in treatment programs.

Compare all specimens

Ranges reflect occasional-to-heavy use patterns from FDA device inserts and SAMHSA-certified lab conventions.
Test typeTypical Naltrexone detection window
Urineany: 1–3 days (oral); injectable releases for weeks
Saliva (Mouth Swab)any: ~1 day
Hair Folliclesrare
Bloodany: ~1 day

Context worth knowing

Naltrexone blocks opioid receptors rather than activating them — it's the opposite of an opioid in screening terms and appears nowhere on employment panels. Treatment programs may monitor levels to verify adherence to monthly injections.

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Medical disclaimer: DrugPanels provides educational information about laboratory drug testing and does not offer medical advice, diagnosis, or treatment. Detection windows are population ranges — individual results vary with metabolism, dose, frequency and health status. Never stop prescribed medication to pass a test without talking to your prescriber. Affiliate disclosure: some links on this page are affiliate links; if you order through them we may earn a commission at no additional cost to you.

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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.

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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)