Cannabis testing guide

THC Drug Testing for Urine, Blood, Hair, and Saliva (Oral Fluid)

If you’re searching “how long does weed stay in your system,” the real answer depends on the test type, the cutoff level (like 50 ng/mL for many urine screens), and your use pattern.

Important: This page is educational and does not provide instructions to “beat” or tamper with a drug test. If you’re worried about a THC test result—or your cannabis use—our team can help you make a safe plan.

Talk to our admissions team See cannabis detection times (all cutoffs)

Reviewed by: A Road To Recovery Rehab Clinical Team Last updated: December 20, 2025

Quick comparison: urine vs blood vs saliva vs hair

Different specimens answer different questions. Some are best for recent exposure (blood/oral fluid). Others look farther back for a history of use (urine/hair).

Test type	What it usually detects	Typical “look-back” window*	Common uses	Big limitations
Urine most common	Primarily THCA/THCCOOH (inactive metabolite)	Days to weeks (varies by use pattern + cutoff)	Workplace screens, probation, compliance monitoring	Does not reliably show impairment or exact last-use time
Blood	THC (and sometimes metabolites)	Hours to (sometimes) days, depending on sensitivity and use history	Medical settings, driving/impairment investigations	THC levels don’t map cleanly to impairment; can persist after effects fade
Saliva / oral fluid	Often THC (recent exposure); may include metabolites	Hours to ~1–2 days in many settings; can be longer with sensitive methods	Roadside testing, some workplaces, observed collections	Cutoffs vary a lot; timing depends on route (smoked vs edible)
Hair	Drug/metabolite incorporated into hair shaft	Up to ~90 days (typical head hair sample)	Pre-employment “pattern of use” screening	Not good for immediate/recent use; takes days to grow out after exposure

*These are general ranges. Your window can be shorter or longer depending on the lab method, cutoff level, and frequency of use.

What THC drug tests actually measure (THC vs THCA/THCCOOH)

THC vs metabolites: why the specimen matters

Urine tests usually look for the inactive metabolite (often called THCA or THCCOOH), not the THC that causes intoxication.
Blood and oral fluid can detect THC closer to the time of use, especially after smoking/vaping.
Hair testing is used to assess longer-term patterns of use (a “look-back” window), not current impairment.

Why this matters: a positive THC-related test is often evidence of prior exposure, but it doesn’t always mean someone is currently impaired—especially for urine tests.

Urine THC testing (including 50 ng/mL)

Urine testing is the most common way employers and programs screen for cannabis exposure. It typically detects THCA/THCCOOH (an inactive metabolite), which can remain measurable after psychoactive effects are gone.

Common regulated cutoffs (example): DOT urine testing uses a 50 ng/mL initial cutoff for marijuana metabolites (THCA) and a 15 ng/mL confirmatory cutoff. (Other employers may use different cutoffs.)

How long does THC stay in urine?

There is no single guaranteed timeline. But in general, urine detection depends on frequency of use, dose/potency, body composition, time since last use, and the cutoff sensitivity.

Use pattern	What many clinicians/refs describe	What changes the window most
Single / one-time use	Often a few days; some controlled data suggest 50 ng/mL screens can be short (around 1–2 days) in certain contexts.	Higher cutoffs shorten the window; lower cutoffs extend it.
Occasional use (e.g., weekends)	Can be several days and sometimes up to ~2 weeks for some people.	Potency, frequency, and time between uses.
Chronic daily use	Commonly weeks; some clinical references describe ~1 month in chronic daily use.	Body fat + long-term accumulation + cutoff sensitivity.

If you need a deeper dive into cutoffs and timelines, see: Cannabis detection times (THC).

Reality check: A urine THC test result alone usually cannot tell you exactly when someone used cannabis. It’s best interpreted as evidence of prior exposure, especially in frequent users.

Blood THC testing

Blood testing can detect THC closer to the time of use than urine, but interpretation is tricky: THC levels don’t correlate cleanly with impairment, and regular users can have detectable THC after effects fade.

Typical detection window

Shorter window: In controlled settings, blood THC detection may be measured in hours (and depends heavily on test sensitivity).
Longer in frequent users: Residual THC can be detectable many hours to days in regular users—even when impairment is no longer present.

Why blood tests exist: They’re often used where the question is “recent exposure” (e.g., medical care or driving investigations), even though the science does not support a simple “THC level = impairment” rule.

Saliva / oral fluid THC testing

“Saliva” testing is typically referred to as oral fluid testing. It is often used because collection is observed and it can detect recent exposure—especially after smoking or vaping.

Federal oral-fluid cutoffs (reference point)

For federal workplace drug testing programs using oral fluid, THC cutoffs include: 4 ng/mL initial and 2 ng/mL confirmatory. Many non-federal programs may use different devices and cutoffs.

How long does THC stay detectable in oral fluid?

Often hours for many people, and in some testing settings it can extend into the next day.
Cutoff level matters: lower cutoffs (more sensitive tests) generally extend the detection window.
Edibles can shift timing (effects start later), but oral fluid results still vary widely by method.

Helpful mental model: Oral fluid is usually better for “recent exposure” than urine, while urine is typically better for “history of exposure.”

Hair testing (“hair follicle” tests)

“Hair follicle test” is a common term, but most workplace “hair tests” analyze the hair shaft that’s cut near the scalp. Hair testing is used to evaluate a longer look-back period—commonly up to about 90 days for head hair.

Key points about hair detection times

Look-back window: A typical head-hair sample (about 1.5 inches) corresponds to roughly 90 days of growth.
Not immediate: It can take roughly 5–10 days after exposure for drug-containing hair to grow out enough to be collected.
Best for patterns: Hair tests are used more for long-term patterns than for “right now” impairment.

If you’re confused by the term: Hair testing is not the same as urine or blood testing, and it answers a different question. If you need help interpreting a specific result, our team can talk it through with you.

What changes THC detection times?

Across all specimen types, the biggest drivers of THC detection time are:

Frequency of use: daily/heavy use generally increases detection time.
Potency + dose: higher THC exposure can extend detection.
Body composition: THC is lipophilic (fat-soluble), which can affect how long metabolites are measurable.
Test cutoff + method: more sensitive tests (lower cutoffs) generally detect longer.
Time since last use: the obvious factor—but it interacts with all the above.
Specimen quality controls: many programs check for dilution or other validity issues.

Myths about “passing” a THC drug test (and why they backfire)

A lot of online advice about “beating” a THC test is unreliable, unsafe, or can trigger invalid/dilute results and retesting. Instead of focusing on shortcuts, focus on accurate information and your health.

We don’t give instructions for tampering: Attempting to manipulate a test can have serious employment, legal, and health consequences. If you’re feeling trapped by testing pressure, you’re not alone—and help is available.

If your worry about a THC test is connected to your cannabis use, you may benefit from support that’s bigger than just “this one test.” See: How to stop smoking weed (withdrawal + recovery plan).

FAQs

What does “50 ng/mL” mean on a THC urine drug test?

“50 ng/mL” is a cutoff concentration used in many urine screening tests for marijuana metabolites (THCA/THCCOOH). If the screen is at or above that cutoff, a more specific confirmatory test may be performed (often with a lower cutoff, such as 15 ng/mL in some regulated programs).

Can a urine THC test tell if I’m currently impaired?

Usually, no. Urine tests primarily detect an inactive metabolite and generally indicate prior exposure—not current intoxication or impairment.

Which THC test “goes back” the farthest?

Hair testing is generally used for the longest look-back window (often around 90 days for head hair), while urine can detect days to weeks depending on use pattern and cutoff.

Can secondhand marijuana smoke cause a positive test?

It’s considered uncommon at standard workplace cutoffs, but some sources note transient positives can happen under extreme, poorly ventilated exposure. Confirmatory testing helps reduce false positives and clarify results.

Can CBD products trigger a THC positive?

Many tests target THC metabolites, not CBD. However, some CBD products may contain THC (even if labeled “hemp”), which can lead to a positive depending on dose, product quality, and test sensitivity.

What should I do if I’m anxious about a THC test?

If you’re dealing with workplace, legal, or family pressure, consider getting support early. We can help you understand timelines, reduce risk going forward, and build a plan for cannabis reduction or recovery. Contact A Road To Recovery Rehab.

Worried about a test—or your weed use?

If cannabis is starting to control your schedule, mood, sleep, motivation, or relationships, it may be time to talk to someone. You don’t have to wait for a crisis.

Get confidential help Read: Cannabis detection times (THC)

Sources

These references are provided for transparency and further reading.