Tetrahydrocannabinol (THC) is the chemical in cannabis that makes people feel “high.” Tests can detect THC 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 much and how often they consume the drug
- the sensitivity of the drug test
Drugs such as alcohol may completely disappear from the body in just a few hours. In comparison, cannabis lingers much longer.
Drug tests can detect 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.
Research on how long a test can detect cannabis shows a wide range of averages. Research from 2017 estimates a detection window for a single cannabis cigarette of about 3 days.
The same study emphasizes that detection windows vary and depend on how often a person smokes. It showed:
- For someone smoking cannabis for the first time, tests may detect it for about 3 days.
- In someone who smokes cannabis 3 or 4 times per week, the detection window is 5–7 days.
- For people who smoke cannabis 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. The
- Urine tests: These tests can detect cannabis in the urine for approximately 1–30 days after use.
- Saliva tests: Typically, cannabis is detectable in saliva for up to 24 hours. However, some evidence suggests an oral test can detect THC from a THC cigarette for up to 30 hours after use. Some saliva tests may also detect cannabis from oral dosing, such as brownies, Sativex, Marinol, for up to 44 hours.
- Hair tests: This type is the most sensitive test, detecting THC for up to 90 days after use. However, older research notes that these test the oil in skin that transfers to hair, 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.
- Sweat tests: Cannabis may be detectable in sweat for 7–14 days.
- Blood tests: A blood test can only detect THC for a few hours.
Drug tests can detect relatively small quantities of THC, and the amount of THC in a given cannabis cigarette varies. However, little research has examined how much a person must smoke to fail a drug test.
Additionally, tests can detect THC for longer periods in individuals who use cannabis products more frequently. This is because chronic cannabis use will result in THC accumulating in fatty tissues, which will result in a slower elimination of metabolites.
Some 77% of heavy users and 39% of light users produced positive tests. No non-users had positive test results, suggesting that false positives in hair tests are relatively rare.
Numerous factors influence whether a test detects cannabis, including the following:
More sensitive tests can detect lower doses of cannabis. Tests include blood, urine, hair, and saliva.
Cannabis drug tests look for THC, not cannabis. So the amount of THC that a person consumes is a significant factor.
The effects of THC are cumulative. This means that a person who smokes several times over several days has consumed a higher THC dose than someone who smokes once, so they are more likely to test positive.
The strength of each dose of THC also matters. Without sensitive laboratory equipment, a person cannot reliably determine the strength of their cannabis.
How “high” a person feels is also not a reliable measure, because numerous factors other than THC dose can intensify or weaken this feeling.
THC is a fat soluble compound, this means that fat cells store cannabis. As such, people with higher body fat concentrations may metabolize cannabis more slowly than a person with less body fat.
Body mass index (BMI) is one way to judge body fat. However, since weight, and therefore BMI, increases with muscle mass, BMI is not a perfect measure of body fat.
Typically, females have more body fat than males. This means that females may metabolize cannabis slightly more slowly.
Dehydration increases concentrations of THC in the body. While drinking lots of water is unlikely to affect a drug test significantly, severe dehydration might.
Exercise will not significantly change the rate at which the body metabolizes THC. Exercising before a drug test, however, might.
For a drug test to be negative, the body must eliminate THC from the system, as well as metabolic chemicals that have links to THC. People with faster metabolisms typically eliminate THC more quickly than those with slower metabolisms.
Ultimately, there is no definitive method to get cannabis out of the body faster. However, strategies that may help to remove cannabis from the body quicker involve breaking down body fat cells, speeding up THC metabolism in the liver, and removing THC metabolites from the intestines.
As the body stores THC in fat cells, regular exercise may help to break fat cells down and release THC into the blood for further excretion. However, while exercise might help the body metabolize more THC, exercising too near to a test may also cause a positive result due to having THC in the bloodstream.
Similarly, following a healthy dietary plan may also help with this process of metabolizing THC. Additionally, consuming fiber can help to improve digestion and promote bowel movements, which can aid in the elimination of THC metabolites from the body.
Drinking sufficient amounts of water may also help to remove THC metabolites through urine and bowel movements. Getting plenty of sleep can also help to avoid any decreases in metabolism.
However, there is no reliable way to speed up the metabolism and excretion of THC. The most important factor is the time from the last exposure to the testing time.
Read on to learn more about a cannabis detox.
There is no way to accurately predict how long it will take an individual to metabolize cannabis and eliminate it from their bodies. Home tests can help people test themselves for the presence of cannabis in their system.
For almost all people, cannabis should disappear or be very low in concentration within 30 days. For infrequent users, it may take 10 days or fewer for cannabis to leave the body.