When we smoke or ingest cannabis, those unique plant compounds interact with our bodies. This interaction is the sole reason humans have turned to cannabis over the centuries for religious purposes, relaxation, pain relief, and recreation. This interaction also explains why cannabinoids and their byproducts remain detectable in the body and in many cases remain well after the buzz wears off.
In order to address the question, “How long does marijuana stay in your system?” we must first focus our attention on THC, or delta-9-tetrahydrocannabinol, the intoxicating cannabinoid known for creating euphoric, stoned effects. Other compounds stick around, too. But because THC remains federally illegal in the US, cannabis drug tests often exclusively screen for THC and THC metabolites, or byproducts that are produced when THC is broken down in the body.
It varies according to dose
Weed, also known as marijuana or cannabis, is usually detectable in bodily fluids for 1 to 30 daysTrusted Source after last use. As with other drugs, it may be detectable in hair for several months.
Weed 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.
For daily users, cannabis may be detectable for several months after last use. The longest-reported detection times are more than 90 days.
How does cannabis travel through the body?
To fully understand how long weed could stay in your system, it’s important to establish how THC travels through and interacts with the human body.
When cannabis is smoked or vaporized, THC enters the bloodstream through the lungs. From there, it is carried in the bloodstream directly to the heart and pumped throughout the body where it binds to the CB1 receptors located in the brain, certain organs, and central nervous system, as well as the CB2 receptors in the spleen and immune system. These receptors are part of the endocannabinoid system.
As blood circulates throughout the body, THC is continuously passed through the liver and broken down into metabolites. To detect the presence of cannabis in the body, most drug screening methods look for one metabolite called 11-nor-9-carboxy-THC, or THC-COOH.
This inactive metabolite of THC, which is stored in body fat and gradually eliminated through urine and feces, remains in the body for far longer than active THC. That’s why so many marijuana detox drinks and kits claim to eliminate or mask the presence of THC metabolites.
The process is slightly different when cannabis is consumed in the form of an edible or capsule. When taken orally, THC enters the bloodstream through the walls of the stomach and intestines, traveling directly to the liver where a large amount is eliminated or metabolized. The remaining THC and THC metabolites are then circulated by the heart and sent to the brain.
How long is it detectable via drug testing?
Drug tests measure weed 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 methodTrusted Source.
According to an article in 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 use of weed.
According to a 2014 reviewTrusted Source 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
Weed 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 weed is legal, oral fluid may be used for roadside testing.
Hair follicle tests assess drug use for up to 90 daysTrusted Source. After use, weed 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 weed use for the past three months.
How long does it take to break down (metabolize)?
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.
What factors affect how long it stays in your system?
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.