Tetrahydrocannabinol, the chemical in marijuana that makes people feel “high,” can stay in the body for several days or even weeks.
The length of time this chemical stays in the body or continues to show in a drug test depends on many factors. These include:
- how much body fat a person has
- how often they consume the drug
- how much someone smokes
- the sensitivity of the drug test
Drugs such as alcohol may completely disappear from the body in just a few hours. In comparison, weed lingers much longer.
Drug tests can detect tetrahydrocannabinol, or THC, in urine, blood, and hair for many days after use, while saliva tests can only detect THC for a few hours. This is because of the way the body metabolizes THC.
THC is a lipid-soluble chemical. This means that it binds to fat in the body, which increases the length of time it takes for someone to eliminate THC completely.
Marijuana detection windows
Research on the amount of time a test can detect marijuana shows a wide range of averages. Research from 2017 estimates a detection window for a single marijuana cigarette of about 3 days.
The same study emphasizes that detection windows vary and depend on how often a person smokes.
- For someone smoking marijuana for the first time, tests may detect it for about 3 days.
- In someone who smokes marijuana three or four times per week, the detection window is 5–7 days.
- For people who smoke marijuana once a day or more, tests may detect it in their system for 30 days or longer.
Detection windows also depend on the kind of test a person undertakes. General estimates for various marijuana tests are as follows:
- Urine tests can detect marijuana in the urine for approximately 3–30 days after use.
- Saliva tests can detect marijuana for approximately 24 hours after use. Some saliva tests have detected marijuana for up to 72 hours.
- Hair tests are the most sensitive tests, detecting THC for up to 90 days after use. However, these tests are testing the oil in skin that transfers to hair, and so they may occasionally show a false positive. A person who comes into contact with a THC user could, theoretically, test positive on a hair test.
- Blood tests can only detect THC for 3–4 hours.