Tetrahydrocannabinol (THC), the psychoactive chemical in marijuana, can remain in the body for days or weeks. Hair tests are the most sensitive screening methods, as they can identify THC for up to 90 days after the last use. These tests examine the composition of the oil in the skin that transfers to hair, so they occasionally may reveal a false positive. Moreover, an individual who comes into regular contact with a marijuana user could test positive on a hair follicle test.
The length of time THC stays in a person’s system or continues to be detectable on a drug screen depends on several factors in addition to the method of testing used. These include how much and how frequently marijuana is ingested, as well as a person’s body fat content. Some substances can be eliminated entirely from the body in just a few hours. However, marijuana is fat-soluble, meaning that it is stored in fatty tissues for an extended period.
Drug tests can detect THC in blood, hair, urine, and hair several days after use. Saliva tests can identify the presence of THC for only a few hours.
Marijuana can remain in the body anywhere from 3-30 days, sometimes longer. Studies on the length of time a test can detect marijuana have revealed a wide range. A 2017 study suggested a detection window of around three days for a single marijuana cigarette. The same study also noted that detection windows vary between individuals and will depend on how often an individual ingests marijuana.
Other findings included the following:
- For a first-time marijuana user, tests may detect it for around 72 hours.
- For an individual who smokes marijuana 3-4 times per week, the detection window is 5-7 days.
- For someone who smokes marijuana daily, tests may detect it in their system for 30 days or longer.
Detection times also depend on the type of test being performed. Estimates for marijuana tests are as follows:
- Urine tests can detect THC in the urine for between 3–30 days after the last use.
- Saliva tests can identify THC for up to 24 hours after use, sometimes longer.
- Blood tests can detect THC for three days.
- Hair follicle tests can detect THC for up to 90 days.
How Much Marijuana Exposure Leads to a Failed Drug Screen?
Most drug screens can identify relatively small THC, and the THC in a given dose of marijuana varies. Some researchers have examined precisely how much an individual must smoke to fail a drug test.
A study from 2012 focused on marijuana users smoking a single joint that was 6.8 percent THC. Urine concentrations of this chemical were highest between 0.6-7.4 hours after smoking. Using a urine test, scientists identified metabolites of THC in 100% of frequent users. Metabolites were also identified in occasional users, but there tended to be fewer.
The study concluded that “THCCOOH, THC-glucuronide, and THCCOOH-glucuronide were measurable in all frequent smokers’ urine and 60%, 100%, and 100% of occasional smokers’ urine samples, respectively.”
Another study from 2017 looked at hair sample testing from 136 marijuana users reporting no use, light use, or heavy use. Investigators cut hair into 1 cm sections to test for exposure of up to 30 days prior.
The results of more than three-quarters (77%) of heavy users and 39% of light users came back positive. No non-users revealed evidence of THC, indicating that, although possible, false positives in hair tests appear to be rare.
Factors That Influence Detection Time
Several factors affect if a test detects the presence of marijuana, including the following:
Test Sensitivity – More sensitive tests can identify lower amounts of THC.
THC Dose – Marijuana drug screens look for the presence of THC, not marijuana itself. Moreover, the amount of THC that an individual ingests is likely the most significant factor. THC’s effects are collective, meaning that someone who smokes several times during a brief period has to ingest higher doses of THC than a person who smokes just once. Therefore, they are more likely to test positive.
While the potency of each THC dose is also a factor, how “high” a person feels is not a reliable tool to measure. Other factors can intensify a marijuana high, especially the use of other drugs or alcohol.
Body Fat Percentage – Because marijuana has a high affinity for fat, individuals with higher body fat concentration may metabolize cannabis at a slower rate than someone leaner. Body mass index (BMI) is a method that can be used to estimate body fat.
However, BMI is not always the best way to measure body fat because weight also increases along with more muscle mass. That said, a person who is overweight is probably going to store more THC in their body than someone is not.
Sex – Typically, females carry more body fat than males. For this reason, women may break down marijuana at a lower rate.
Hydration Levels – Dehydration raises levels of THC in the body. While drinking copious amounts of water is not likely to affect a drug screen in any significant way, being severely dehydrated might.
Moreover, proper hydration can prevent a drug screen from revealing unusually high concentrations of THC. For people whose test results border on positive and negative, this could suggest that being dehydrated may increase the likelihood of testing positive.
Exercise – Exercise is not believed to impact the rate at which the body metabolizes THC significantly, but engaging in exercise right before a drug screen may affect it. One small study of 14 regular marijuana users focused on the effects of 35 minutes of exercise on a stationary bike.
Findings revealed that THC levels increased significantly, suggesting that exercising right before a drug test may raise the risk of testing positive. Experts posit that exercise may prompt fat cells to release THC. In fact, individuals with higher BMIs in the study had more significant increases in THC.
Metabolism – For a drug screen to have negative results, the body must clear THC from the system and its associated metabolites. Persons with faster rates of metabolism will tend to eliminate THC more rapidly than those with lower rates.
Unfortunately, there is no reliable way to accelerate a person’s metabolic rate. Exercise might help the body metabolize more THC, but, as we have discussed, exercising right before a test may increase the likelihood of producing a positive result. In the end, the most significant factors are the time between the last exposure to the drug screen and the type of test being conducted.
Treatment for Marijuana Abuse
If you fear failing an upcoming drug test and have been unable to stop using marijuana, you should consider seeking professional help. Although marijuana’s potential for causing dependence and addiction is believed to be relatively low compared to most other drugs, use can become habit-forming. Some people find it challenging to quit using when they want to.
Just Believe Detox and Just Believe Recovery specialize in the treatment of drug and alcohol abuse. We are also equipped to treat co-existing mental health disorders and provide emotional and social support. We offer therapeutic services, such as psychotherapy, counseling, group support, and mindfulness therapy, aimed at helping individuals uncover the root causes of their addictions.
If you are struggling with marijuana abuse, please contact us today! Discover how we help people break free from the chains of addiction for life! Call: 877-497-6180