THC drug test

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 chemicalTrusted Source. 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.

It showed:

• 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 positiveTrusted Source. 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 3–4Trusted Source hours.

How much do you have to smoke to fail a drug test?

Drug tests can detect relatively small quantities of THC, and the amount of THC in a given marijuana cigarette varies. However, little research has examined exactly how much a person must smoke to fail a drug test.

Studies consistently find that frequent weed users are more likely to fail drug tests than infrequent users. A 2012 study in the journal Clinical Chemistry examines marijuana users smoking a single cigarette with 6.8 percent THC.

Urine concentrations of THC were highest 0.6 to 7.4 hours after smoking. Using a highly sensitive urine test, researchers detected THC in the urine of 100 percent of frequent users and 60–100 percent of infrequent users.

A 2017 studyTrusted Source reports on testing where hair samples from 136 marijuana users reporting heavy, light, or no use of marijuana. For the study, researchers cut hair into 1-centimeter sections to test for exposure of up to a month prior.

Some 77 percent of heavy users and 39 percent of light users produced positive tests. No non-users had positive test results, suggesting that false positives in hair tests are relatively rare.

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”)
• Relaxation
• Stimulation
• 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.

It is important to know that not all marijuana is created equal. Unlike other prescription drugs, marijuana products aren’t standardized and can vary considerably in quality, makeup, and dosage.

This variance may contribute to how quickly you feel the effects and what those effects are. THC can interact with alcohol, blood thinners, and anti-anxiety medications, so it’s important to discuss your marijuana use with your doctor.

How Long Does Marijuana Last?

The half-life of marijuana is how long it takes for half of the drug to be metabolized and eliminated from the bloodstream. While there are many different cannabinoids, THC is the one most drug tests are looking for.

THC is rapidly broken down and modified into molecules known as metabolites. At least 80 different metabolites are formed from THC and may have their own effects on the body’s endocannabinoid system. These metabolites are stored in body fat and are gradually eliminated from the body through feces and urine.

Some THC metabolites have an elimination half-life of 20 hours whereas others are stored in body fat and have an elimination half-life of 10 to 13 days.

It takes five to six half-lives for a substance to be almost entirely eliminated. This is why you see advice that one-time use is probably not detectable after five to eight days.

Blood and Saliva

Because marijuana stays in the bloodstream for only a short time, blood tests for marijuana are usually not used. The exceptions are in the case of automobile accidents and some roadside sobriety checkpoints.

Blood or saliva tests can show current intoxication. However, unlike blood alcohol concentration tests, they do not indicate a level of intoxication or impairment.

Hair

Daily or near-daily cannabis consumption is likely, but not always, detectable by a hair test up to three months later. But, the hair test is not reliably able to detect infrequent cannabis use or determine the amount of cannabis used.

Urine

Urine tests for marijuana metabolites also only show recent marijuana use, not current intoxication or impairment. This is because of the time required between use and your body breaking down THC to the metabolites that are eliminated in the urine. Because many employers have a zero-tolerance for drug use, most workplaces use urine tests to detect recent use of drugs.

False Positive Testing

Workplace testing for marijuana might entail first screening the sample with an immunoassay test, known as the EMIT or RIA. If positive results are returned, the sample is again screened with a gas chromatograph-mass spectrometer (GCMS), which is much more accurate and so false positives are rare.

No known substances would cause a marijuana urine test to return a false positive.

At one time, ibuprofen (sold over-the-counter as Advil, Motrin, and Nuprin) would cause false marijuana positives. But today’s tests have been adjusted to eliminate that problem.

In places where marijuana is legal, roadside blood tests have been known to show some false positives in people who had been legally consuming cannabis but were not actively intoxicated at the time of the test. A 2016 report detailed a Belgian policy of testing oral fluid at the roadside that found it decreased these types of false positives.

Factors That Affect Detection Time

The length of time marijuana remains in your body depends on many different factors, including frequency of use, body mass, metabolism, sex, and hydration levels.

Frequency of Use

There is some evidence that the length of time that marijuana remains in the body is affected by how often the person uses marijuana, how much they use, and how long they have been using.

People who use marijuana regularly have reported positive drug test results after 45 days since last use, and people who use more heavily have reported positive tests up to 90 days after quitting.

In a 2017 study of 136 people who use cannabis subjected to hair tests, the presence of five cannabinoids, THC, THC-OH, THC-COOH, cannabinol, and cannabidiol, were present in 77% of the heavy users and 39% of the light users.

Sex

Women often metabolize THC at a slightly slower rate since they tend to have higher levels of body fat than male counterparts.

Metabolism

The faster your metabolism, which can be impacted by age, physical activity, and certain health conditions, the faster marijuana will exit your body. 

Body Mass Index (BMI)

THC metabolites are often stored in the fat cells in your body, so the higher your body fat (or BMI), the slower you’ll likely be able to metabolize and excrete marijuana.

Hydration

When you’re dehydrated, you’ll have more concentrations of THC in the body. Flooding yourself with water won’t make you pass a drug test, however. Instead, it will dilute it and you’ll likely need to retake the test.

Smoking vs. Vaping vs. Edibles

The method of use also impacts the detection time. If marijuana is smoked or vaped, the THC levels in the body will drop faster than if you ingest it. Edibles take longer to break down in the body and leave your system.