Marijuana, also known as cannabis or weed, is usually detectable in bodily fluids for 1 to 30 days after last use. As with other drugs, it may be detectable in hair for several months.
Marijuana detection windows depend on how much you smoke or ingest, as well as how often. In general, higher doses and more frequent use are associated with longer detection times.
Read on to find out the detection windows for cannabis in urine, blood, saliva, hair, and more.
Drug tests measure marijuana and its by-products, or metabolites. These metabolites remain in your system long after weed’s effects have worn off.
According to Mayo Clinic Proceedings, weed is detectable in urine for the following amounts of time after last use:
- Occasional users (up to three times a week): 3 days
- Moderate users (four times a week): 5 to 7 days
- Chronic users (daily): 10 to 15 days
- Chronic heavy users (multiple times a day): more than 30 days
Cannabis metabolites are fat-soluble, which means they bind to fat molecules in your body. As a result, it can take some time for them to leave your system.
Urine testing is the most common testing method.
According to Therapeutic Drug Monitoring, weed is typically detectable in the blood for 1 to 2 days. However, in some cases, it’s been detected after 25 days. Chronic heavy use increases the length of time that it can be detected.
Weed is detectable in the bloodstream within seconds of inhalation. It’s distributed to the tissues. Some of it is reabsorbed in the blood and broken down. Its metabolites may remain in the bloodstream for days.
Blood testing may be used in laboratory settings or to indicate recent marijuana use.
According to a 2014 review on cannabinoids in oral fluid, weed is detectable in saliva for the following amounts of time after last use:
- Occasional users: 1 to 3 days
- Chronic users: 1 to 29 days
Marijuana can enter the saliva through smoking and exposure to smoke. However, its metabolites are only present in saliva when weed has been smoked or ingested.
In jurisdictions where marijuana is legal, oral fluid may be used for roadside testing.
Hair follicle tests assess drug use for up to 90 days. After use, marijuana reaches the hair follicles via small blood vessels. Trace amounts may remain in the hair.
Since hair grows approximately 0.5 inches per month, a 1.5-inch hair segment taken close to the scalp can provide a window of marijuana use for the past three months.
The active ingredient in weed is a chemical substance called THC, which stands for delta-9-tetrahydrocannabinol. THC that enters your body is absorbed into the bloodstream.
Some THC is temporarily stored in organs and fatty tissues. In the kidneys, THC can be reabsorbed into the bloodstream.
THC is broken down in the liver. It has more than 80 metabolites, but the most significant ones are 11-OH-THC (11-hydroxy-delta-9-tetrahydrocannabinol) and THCCOOH (11-nor-9-carboxy-delta-9-tetrahydrocannabinol).
Drug tests look for these metabolites, which stay in your body longer than THC. Eventually, THC and its metabolites are excreted in urine and stool.
A number of factors affect how long weed stays in your system. Some of these factors, such as your age, gender, and body mass index (BMI), aren’t related to the drug itself, but to how your body processes and metabolizes the drug.
Other factors are related to weed and how you use it. This includes how much you take (dose) and how often (frequency). Higher doses and more frequent use tend to increase the amount of time it takes to eliminate weed from your system.
More potent weed, which is higher in THC, may also stay in your system for longer. Weed that’s ingested may also remain in your system slightly longer than weed that’s smoked.
There isn’t much you can do to speed up the amount of time it takes for weed to leave your system.
Once it’s entered your system, your body needs time to break it down. Exercising, eating healthy, and staying hydrated may help, but not drastically.
There are a number of weed detox remedies and kits and available on the internet. Many require drinking a lot of water to dilute your urine, and then using herbal supplements such as creatinine or vitamin B-12 to mask the dilution.
These kits don’t work reliably.
Weed’s active ingredients produce a short-term “high.” Common effects include:
- sense of well-being
- sense of relaxation
- feeling that time is slowing down
- giggling or chattiness
- altered sensory perception
Other short-term effects include:
- inability to focus
- increased appetite
- coordination problems
- rapid heart rate
- dry mouth and eyes
- feeling sick or faint
- anxiety or paranoia
In rare cases, high doses of weed can cause delusions and psychosis.
Smoking or ingesting weed on a regular basis can have additional effects on your mind and body. You might be at an increased risk of developing:
- cognitive impairments
- memory impairments
- learning impairments
- cardiovascular diseases, such as heart disease and stroke
- respiratory illnesses, such as bronchitis and lung infections
- mood disorders, such as depression and anxiety
- hallucinations and psychosis
Researchers don’t know how long the effects of chronic marijuana use last. Long-term effects can last days, weeks, or months after weed use has ended. Some effects may be permanent.
Weed may stay in your system anywhere from several days to several months after last use. Detection windows depend on the drug test used and other factors, such as whether you smoke or ingest weed on a regular basis.