THC stays detectable for a few hours to several months, depending on the test: briefly in saliva and blood, days to weeks in urine, up to about three months in hair. So how long does weed stay in your system? Two things decide it – the type of test and how often you use cannabis.
Cannabis, weed or hash: the substance is always tetrahydrocannabinol (THC) and its metabolite THC-COOH. Below we explain how long THC stays in your body per test type, the Swiss legal limit and what CBD products mean for a drug test. What THC itself is, our basics article on tetrahydrocannabinol explains; this page covers detection only. New to Switzerland? CBD products with under 1% THC are legal here, while THC-rich cannabis remains controlled.
How Long Does Weed Stay in Your System?
THC stays in your system for hours to months, depending on the test: saliva and blood show use from the last hours to days, urine from the last days to weeks, and hair from the last few months. The range is wide because the tests measure different things – some look for active THC, others for its metabolite THC-COOH.
The overview below gives the typical THC detection window for each test. How long does THC stay in your system if you use cannabis regularly? Considerably longer, because every window shifts upwards with frequency of use.
| Test type | What is measured | One-off use | Regular use |
|---|---|---|---|
| Saliva | active THC from the mouth | hours | hours to a few days |
| Blood | active THC, THC-COOH | hours (active THC) | several days |
| Urine | THC-COOH | about 1.5 to 4 days | several weeks |
| Hair | THC, THC-COOH in the hair shaft | often not detected | up to about 90 days (3 cm of hair) |
The blood and urine values come from a review of controlled human studies by Marilyn Huestis, published in Chemistry & Biodiversity in 2007 [1]. They are typical ranges from the literature, not a guarantee for any individual.
THC Metabolism: Half-Life, Fat Storage and THC-COOH
How long does it take for weed to be cleared from the body? Days to weeks, because THC is fat-soluble: it is stored in fat tissue and released slowly back into the blood. That slow release is why traces remain measurable long after the last use, even though the active compound itself leaves the bloodstream quickly.
The breakdown runs through the liver. There, THC is first converted into 11-OH-THC and then into the metabolite THC-COOH. THC-COOH is not intoxicating, but it stays measurable for much longer than THC itself – and THC-COOH is exactly what most drug tests look for, above all in urine.
This is why a urine test can still react when active THC in the blood has long fallen below the detection limit. With regular use, elimination is slower still: Huestis (2007) reports a terminal plasma half-life of THC of 4.1 days in chronic users, because their fat stores hold more of it [1]. How long THC-COOH stays in your system therefore depends less on the last dose than on how much has built up over time.
Smoked Weed Once vs Daily Use: How Frequency Changes Detection
Frequency of use is the biggest lever on detection time: in urine, a single joint and daily use sit weeks apart. The more often THC is used, the longer each detection window becomes – every step from one-off to occasional to daily use lengthens it.
| Pattern of use | Urine (THC-COOH, cut-off 15 ng/ml) | Blood (active THC) |
|---|---|---|
| Once | on average about 1.5 to 4 days | a few hours |
| Occasional | between these values, depending on frequency | hours to about a day |
| Daily, including one joint a day | several weeks, in single cases over 60 days | several days |
The values for one-off and daily use come from Huestis (2007) [1]. In a controlled study, the last positive urine sample after a single cigarette came on average at 33.7 or 88.6 hours, depending on its THC content; in one heavy long-term user, an immunoassay still read positive 67 days after the last use. So if you smoked weed once, a drug test usually reads that use for days, not weeks – while anyone using daily, even one joint a day, counts as a regular user, and the window then runs to weeks.
Beyond frequency, other factors shift the edges: the amount and THC strength of what was used, body fat, individual metabolism and the cut-off value the laboratory applies.
How Long Do Edibles Stay in Your System?
How long edibles stay in your system follows the same rule as smoked cannabis: the dose and how often you use them decide the window. What changes is the route. Eaten THC is absorbed more slowly and passes through the liver before reaching the bloodstream, so more of it is converted into 11-OH-THC on that first pass, as Huestis describes in her 2007 review [1]. uWeed sells no THC edibles; this is detection fact only.
THC Drug Tests: Four Test Types Compared
A THC drug test looks either for active THC or for its metabolite THC-COOH – never for CBD. Saliva and blood show recent use, while urine and hair look into the past. Most testing starts with a rapid screening test (immunoassay), and a laboratory then confirms a positive result with GC-MS. The sweat patch is a fifth, rarely used method.
How Long Does THC Stay in Your Blood?
After one-off use, active THC usually stays in your blood for hours to about a day; with regular use it remains measurable for several days, and THC-COOH stays in the blood longer still. So when you ask how long THC stays in blood for a drug test, the short answer is that a THC blood test mainly reads recent use.
Huestis (2007) shows that plasma levels fall to 5 ng/ml or less within two hours of a single cigarette [1]. The claim that THC is only in your blood for three to four hours is therefore too short: low levels remain measurable after that.
In Switzerland the biology is the same as anywhere else. What is specific here is that a blood test decides whether the legal limit in road traffic has been exceeded, which is why it is the test the authorities order when they suspect drug use.
THC Blood Levels: The Swiss 1.5 µg/L Limit
Blood figures are a legal and measurement value: they say when a reading counts in law, not when someone may do something again.
| Measure | Typical value | Source |
|---|---|---|
| Swiss road-traffic limit | 1.5 µg THC per litre of whole blood | Art. 34 VSKV-ASTRA (SR 741.013.1) [2] |
| Peak plasma level after one cigarette | on average 84 to 162 ng/ml | Huestis 2007 [1] |
| Plasma level two hours after one cigarette | 5 ng/ml or less | Huestis 2007 [1] |
The units are interchangeable, since 1 µg/L equals 1 ng/ml. The 1.5 µg/L figure is a legal value, not a guide for use; the often-quoted 3.5 ng/ml applies in Germany, not in Switzerland.
How Long Does THC Stay in Urine?
THC-COOH stays in urine for a few days after one-off use and for weeks with regular use. The urine test is the most common test and, after hair, has the longest memory, because it looks for the metabolite rather than the active compound. How long weed stays in your system for a urine test therefore depends above all on frequency.
What decides the result are the cut-off values, shown in the table below. A rapid test is often read as positive from 50 ng/ml of THC-COOH, while laboratory confirmation by GC-MS works with 15 ng/ml; values below these count as negative.
| Stage | THC-COOH cut-off | Method |
|---|---|---|
| Rapid test | often 50 ng/ml | immunoassay |
| Confirmation | 15 ng/ml | GC-MS in the laboratory |
Swiss laboratories use the same methods as laboratories elsewhere, so the windows are the same. A positive rapid test is only an indication; what counts is the laboratory confirmation.
How Long Does THC Stay in Saliva?
THC stays detectable in saliva mainly in the hours after use, because a saliva test measures active THC from the mouth rather than the metabolite THC-COOH. That makes it the shortest window of the four test types.
At a roadside check in Switzerland, the saliva test – often called a mouth swab or roadside drug test – is a pre-test. It gives a fast answer but no proof: if it reads positive, the police order a blood sample, and only the blood value counts from then on.
How Long Does THC Stay in Your Hair?
THC stays in your hair for months, because a hair test looks back rather than at today. Scalp hair grows about 1 cm a month, and a typical sample of around 3 cm covers roughly 90 days. A hair analysis shows patterns of use over months, while a single use is often not detected at all.
Hair tests are used mainly in driving-fitness assessments and as proof of abstinence. The claim sometimes found online that THC shows in hair for only three days after a single joint is wrong.
THC Testing in Switzerland: Roadside Checks, Workplace and Legal Limit
Where and why you are tested in Switzerland decides which test is used and which value counts. Testing follows different rules on the road and at work, and if you have moved here from another country, the figures you know may not apply.
On the road, a check usually starts with a saliva pre-test, followed by a blood sample. What counts is the limit of 1.5 µg THC per litre of whole blood set in Art. 34 of the FEDRO ordinance on road traffic controls (VSKV-ASTRA) [2]. What this means for CBD products behind the wheel is explained in detail in our article on CBD and driving in Switzerland.
At work, the framework is narrow. Under Art. 328b of the Swiss Code of Obligations, an employer may only process data about you as far as it concerns your suitability for the job [3]. A drug test therefore needs an objective reason, such as safety-critical work, and your consent. Many people ask about all of this with CBD products in mind – which is what the next section covers.
Can CBD Make You Fail a Drug Test?
CBD itself cannot make you fail a drug test, because standard drug tests look for THC, not CBD – but a positive result can come from the THC traces a CBD product may contain. A positive test after CBD use always traces back to residual THC, in a rapid test as in a laboratory analysis.
Swiss CBD products may legally contain under 1% THC. That is a legal fact, not a quality promise. Which rules apply to which product categories is explained in our overview of whether CBD is legal in Switzerland. Whether traces of THC under 1% become measurable in a test depends on the composition, the amount and the frequency of use, so nobody can guarantee a negative result.
Smoking CBD is no exception: CBD flowers come from hemp with under 1% THC and carry THC traces with them. What matters is the THC value in the strain’s lab report, which we publish for each product in our CBD flowers range whenever the brand supplies one.
Does CBD Show Up on a Drug Test?
CBD does not show up on a standard drug test, because standard tests check for THC-COOH and do not look for cannabidiol at all. CBD would only be measurable with a targeted laboratory analysis, which drug testing does not normally include – CBD is not on any standard panel.
CBD and THC are different cannabinoids with different chemical structures, so a test looking for THC-COOH does not read CBD as THC. What separates the two compounds is set out in our article on the difference between CBD and THC. How long CBD itself would stay in urine is irrelevant for a drug test: only the THC share of the product matters, and that depends on its composition.
Full-Spectrum, Broad-Spectrum and Isolate: THC Content Compared
CBD products fall into three levels of THC content, from more to less: full-spectrum, broad-spectrum and isolate. Composition is the one variable you can know before you buy, and it decides the THC share – not a test result. A full-spectrum CBD oil keeps the plant’s whole cannabinoid profile, THC traces under 1% included.
| Spectrum | Contains | THC share | Note |
|---|---|---|---|
| Full-spectrum | whole cannabinoid profile, including THC | under 1% | THC value in the lab report |
| Broad-spectrum | CBD and other cannabinoids, THC removed | below the manufacturer lab's detection limit | not the same as zero |
| Isolate | pure cannabidiol | usually below the detection limit | purity in the lab report |
In broad-spectrum products THC is removed, which technically means below the detection limit of the manufacturer’s laboratory, not zero. The actual value of a broad-spectrum CBD oil only shows in its certificate of analysis.
Isolate is pure cannabidiol, usually sold as crystals or powder, and its purity is determined in the laboratory. With a CBD isolate, too, check the lab report for each product’s value: composition is a product property, not a test guarantee.
Common Myths About Cannabis Drug Tests
The most widespread beliefs about THC detection do not hold up – above all the idea that you can speed up the breakdown.
“Water, detox drinks or home remedies get THC out of your system faster.” Drinking only dilutes urine for a while and does not speed up the breakdown of THC-COOH; laboratories recognise a heavily diluted sample by its low creatinine value, as a human study by Edward Cone and colleagues in the Journal of Analytical Toxicology showed in 1998 [4].
“Exercise or a sauna sweats THC out of your fat.” In a small human study of six daily cannabis users, published in Basic & Clinical Pharmacology & Toxicology in 2014, Westin and colleagues found that exercise and fasting changed blood THC levels too little to matter for drug testing [5].
“A blood test only shows the last few hours.” With regular use, active THC can remain measurable in the blood for several days.
“CBD products are invisible to drug tests.” CBD is, but THC traces are not necessarily – that depends on the spectrum.
No verified method shortens the detection window: the time since the last use is the only factor that counts. HHC, finally, is a different, semi-synthetic cannabinoid that has been controlled under Swiss narcotics law since 31 March 2023 (BetmVV-EDI) [6], and uWeed does not sell it.
The Bottom Line: Test Type and Frequency Decide Detection Time
How long does weed stay in your system? Test type and frequency of use decide: saliva and blood show hours to days, urine days to weeks and hair months, because the tests measure either active THC or the metabolite THC-COOH. In Switzerland, the road-traffic value is 1.5 µg/L in blood. For CBD products, it is the THC share that counts, not the CBD – and for CBD oil from Switzerland, the lab report shows each product’s THC value. When you buy CBD in Switzerland at uWeed, each product page shows the THC value before you order.
Sources and Legal Basis for THC Detection
These studies and legal sources are cited in this article:
- Huestis MA (2007): Human Cannabinoid Pharmacokinetics. Chemistry & Biodiversity 4(8): 1770–1804.
- Verordnung des ASTRA zur Strassenverkehrskontrollverordnung (VSKV-ASTRA), SR 741.013.1 – FEDRO ordinance on road traffic controls, no official English version, Art. 34, consulted on 23.10.2026.
- Swiss Code of Obligations (CO), SR 220, Art. 328b, consulted on 23.10.2026.
- Cone EJ, Lange R, Darwin WD (1998): In Vivo Adulteration: Excess Fluid Ingestion Causes False-Negative Marijuana and Cocaine Urine Test Results. Journal of Analytical Toxicology 22(6): 460–473.
- Westin AA, Mjønes G, Burchardt O, Fuskevåg OM, Slørdal L (2014): Can Physical Exercise or Food Deprivation Cause Release of Fat-Stored Cannabinoids? Basic & Clinical Pharmacology & Toxicology 115(5): 467–471.
- Ordinance of the FDHA on the Lists of Narcotics, Psychotropic Substances, Precursors and Auxiliary Chemicals (BetmVV-EDI), SR 812.121.11, consulted on 23.10.2026.
