How Long Does Cannabis Stay in Your System? Detection Windows Explained

## The Short Answer Cannabis detection windows depend on the test type, the consumer's usage pattern, body composition, and metabolism. For adults 21 and older subject to drug testing, the ballpark ranges: urine tests can detect metabolites for days to weeks (longer for heavy users), blood tests for hours to days, saliva for hours to days, hair for months. Detection is not the same as impairment. ## By Test Type **Urine test (most common).** - Occasional use (once a week or less): 3-7 days. - Moderate use (few times per week): 7-21 days. - Heavy use (daily): 30+ days, sometimes longer. Urine tests detect THC metabolites, which are fat-soluble and accumulate over time. This is why heavy users have the longest detection windows. **Oral fluid (saliva) test.** - Detects THC directly, not metabolites. - Detection window: typically 24-72 hours after last use. - More relevant to recent use than urine tests. **Blood test.** - Detects active THC. - Detection window: typically hours to 1-2 days. - Most closely correlates with active impairment. - Used in some DUI contexts. **Hair follicle test.** - Detects metabolites incorporated into hair. - Detection window: up to 90 days. - Less commonly used for cannabis. - Cannot detect very recent use (takes time for metabolites to reach hair). ## Factors That Affect Detection **Frequency of use.** Single use clears faster than pattern use. **Amount used.** Higher doses take longer to clear. **Body composition.** THC metabolites are fat-soluble; higher body fat percentage can extend detection in some test types. **Metabolism.** Individual variation in liver enzyme activity affects clearance speed. **Hydration.** Affects urine concentration but not total metabolite presence. **Exercise.** Can temporarily release stored THC metabolites from fat tissue, potentially extending detection in some scenarios. ## Passive Exposure Secondhand smoke exposure can produce detectable levels in some test types under extreme conditions (poorly-ventilated room, heavy smoker, sensitive tests), but realistic normal secondhand exposure rarely produces positive results on standard tests. ## Detection vs Impairment A key point: **detection is not impairment.** A chronic consumer can have detectable THC metabolites weeks after last use with no current impairment. An occasional consumer can be impaired at levels below chronic-user baseline. This gap matters in employment, DUI, and custody contexts. Per-se THC limits (automatic DUI at specific blood THC levels) have been criticized for conflating detection with impairment. ## If You're Drug Tested For adults 21+ subject to testing: - **Know your test type.** Different windows. - **Know your timing.** When were you last tested? When's the next? - **Don't assume "I stopped a week ago" is enough.** Heavy use has much longer windows. - **Don't try to beat tests.** Adulterants, detox drinks, etc. are often themselves detectable and can produce worse outcomes. - **For safety-sensitive jobs** (federal employees, DOT-regulated transportation, healthcare), don't use cannabis at all. ## Where to Go Next Related reading: [cannabis in the workplace](/blog/cannabis-in-the-workplace-drug-testing-employment-law-and-your-rights), [cannabis and driving laws](/blog/cannabis-and-driving-laws-risks-and-what-the-research-shows), and [cannabis tolerance breaks](/blog/cannabis-tolerance-breaks-what-they-are-and-how-to-take-one). --- *This article is consumer education for adults 21+. Nothing here is medical, legal, or financial advice. Cannabis laws vary by state, always verify your state's current rules and, for health questions, consult a licensed clinician. For regulated New York retail, verify licensing via the OCM QR-code system at [cannabis.ny.gov](https://cannabis.ny.gov).*