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.
Read on to find out the detection windows for cannabis in urine, blood, saliva, hair, and more.
The effects of marijuana fade quickly, but the drug can be detected in the body for weeks and sometimes longer. The amount of time the active ingredients and breakdown products of weed remain in the system can range from a few hours to 90 days, depending on how often or how much marijuana the person has been using.
Although a number of states in the U.S. have active medical marijuana laws and recreational use of marijuana for adults over the age of 21 is legal in 11 states, Washington, DC, the Northern Mariana Islands, and Guam, the federal government continues to classify marijuana as a Schedule I controlled substance.
According to the Substance Abuse and Mental Health Services Administration (SAMHSA), roughly 1 in 10 people who use marijuana will become addicted—and these rates rise to 1 in 6 if they start using the drug prior to age 18.
The FDA has not yet approved medical marijuana for any medical indication, but it is often prescribed for chronic pain, nausea, HIV, multiple sclerosis, glaucoma, and irritable bowel syndrome (IBS).
How Long Does It Take to Feel the Effects?
The effects of marijuana can vary from person to person. Some people may feel euphoric and relaxed while others feel anxious and paranoid. In other cases, people report feeling “dopey” and experience a loss of interest in activities or an inability to grasp concepts.
The chemical in marijuana that makes you feel “high” is tetrahydrocannabinol, also called delta-9-THC or simply THC. It enters the body’s bloodstream rapidly after smoking marijuana.
If marijuana is ingested orally rather than smoked, it takes longer to be absorbed into the blood, usually from 20 minutes to an hour and a half, but this can vary based on the amount taken as well as physiological factors such as absorption and rates of metabolism and excretion can influence drug concentrations in circulation.
Effects can be far-ranging depending on the strain, method of consumption, and amount and can include the following:
- Dry mouth
- Swollen eyelids
- Bloodshot eyes
- Pleasurable body sensations
- Increased appetite (“the munchies”)
- Distorted perception (sights, sounds, time, touch)
- Loss of coordination
- Trouble with thinking, memory, and problem-solving
- Increased heart rate
The short-term effects of marijuana on memory, learning, problem-solving, and coordination last for one to two hours, with some lingering effects for up to 24 hours. It’s been shown to impair your driving performance for up to three hours, according to the National Highway Safety Administration.
The effects of marijuana are also influenced by the terpene profiles of a given strain. For instance, citrus terpene profiles tend to be more stimulating, which may be the desired effect, or may contribute to someone feeling anxious.
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.
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.
When Will Marijuana Show Up on a Drug Test?
Several different sampling types are used to test for the presence of marijuana. These tests vary in the timeframe during which they can detect marijuana and its metabolites in a person’s system.
- Saliva test: A person can test positive for weed for up to 34-48 hours after last use.
- Urine test: This is the most common drug test used. Infrequent users (less than 2 times/week) can test positive for 1-3 days. A moderate user (several times per week) can test positive for 7–21 days after last use. A heavy user can test positive for a month or longer after last use. People who eat marijuana may produce a positive result for 1-5 days.
- Hair test: Marijuana can be detected on a hair test for up to 90 days. However, studies have argued that a hair test is most reliable for daily or near-daily users and is not as likely to detect the presence of marijuana in light users.
- Blood test: Marijuana and its metabolites can show up on a blood test for up to 36 hours.
Besides the type of test, other factors that can affect how long marijuana will show up on a drug screen include:
- Amount of THC in the marijuana.
- Frequency of use.
- Length of time since last use.
- How quickly the person’s system processes THC.
- Level of hydration.