How long can you test positive for marijuana on a drug test?
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As cannabis users face drug tests from their employers, many people are asking:
How long does weed stay in your system?
The Short Answer:
Urinalysis test: 4-6 weeks, tests for THC metabolites by analyzing urine
Blood test: Usually up to 7 days, though occasionally up to 4 weeks, tests for THC and/or metabolites by analyzing blood
Mouth Swab / Saliva / Oral Fluid test: Usually 24-48 hours, though occasionally 96 hours to 8 days, tests for THC by analyzing saliva
Breath test: 3-4 hours, tests for THC, however ineffective for vaped and edible cannabis by analyzing breath
Hair Follicle test: 3-4 months, tests for THC metabolites by analyzing hair (fingernails are also occasionally used)
Eye Test: During the experienced impairment only, tests eyes for signs of marijuana impairment
Note: Weed is notorious for staying in the body for a very long time. THC tests are only able to check for prior use, they cannot detect impairment. In places where marijuana is legal, the only fair way to test employees is to use an active impairment test, like Gaize. All other THC tests will show use for days to months after the last use.
What factors influence how long weed stays in your system?
The question of how long weed stays in your system depends on several factors related to your individual physiology and patterns of use:
Metabolitic Rate: People with faster metabolisms tend to expel THC more quickly, while those with slower metabolisms retain cannabis metabolites for longer periods.
Body Mass Index (BMI): THC is fat-soluble and can be stored in fatty tissues. Individuals with higher BMIs generally have detectable THC levels for an extended time after use. Conversely, those with low body fat will have less inherent ability to store THC after use.
Frequency of Use: Chronic, heavy marijuana users will have THC remain in their systems longer compared to infrequent, occasional users.
Dosage and Potency: Consuming larger doses of more potent cannabis products leads to higher THC levels that take longer to fully metabolize and eliminate.
Method of Consumption: Smoking marijuana results in a faster metabolism of THC versus ingesting edibles, which undergo additional metabolism by the liver.
Age: Older individuals tend to metabolize and excrete THC more slowly on average.
Gender: Due to differences in body fat percentage, females often metabolize THC at a slower rate than males.
Hydration Levels: Being well-hydrated can help flush out THC metabolites faster compared to dehydration.
Genetics: Each person's unique genetic makeup influences how efficiently they metabolize and eliminate substances like THC.
Clearly, some of the factors influencing the amount of time that marijuana stays in your system are not possible to change. Others, however, are possible to influence. If you’re facing a THC test, it may be helpful to work out, drink lots of water, and stop using marijuana.
Worried about passing a marijuana test from your employer?
Testing for THC by employers has long been the only way they have to maintain a workplace free from drug use. Now, with marijuana being legal in much of the world, simply testing for THC is unfair, discriminatory, and in some states even illegal. Think of it this way: taking adverse action against an employee based on the presence of THC in their body is like telling someone that they can’t have a beer after work. That’s totally unfair and employees are demanding better. Just as you can responsibly consume alcohol on your off time, marijuana users can responsibly use weed on their personal time.
If your employer still tests for THC using chemical drug tests, encourage them to adopt Impairment Detection Technology, like Gaize. Our product is an eye test for impairment that only works when someone is actively too high to be driving or working. It’s being used by employers all over the world to enable safe marijuana use by their employees. Using Gaize, marijuana users can safely consume weed and be verified to be safe to work.
So, if you’re a marijuana user that would like fair treatment at work, recommend Gaize to your HR team.
How to recommend Impairment Detection Technology to your employer:
Make them aware of the shortcomings of traditional chemical drug tests.
Provide an alternative way to keep the workplace safe - Impairment Detection Technology.
Mention the fact that many states are making it illegal to take adverse action against employees for the simple presence of THC in the body.
Note the cost savings available for those that adopt Impairment Detection Technology.
If appropriate, feel free to contact Gaize and we’ll reach out to the appropriate person in your company.
The long answer:
Marijuana testing is extremely commonplace for many workplaces and in case a police officer suspects that you could be driving while impaired. However, not all cannabis tests are created equal. They have massively variable windows in which THC, the impairing molecule in cannabis, and its metabolites may be detected. This causes obvious problems, particularly in states where cannabis is legal. Formerly, an employer or police officer simply needed to find the presence of THC to show that a crime or workplace violation had been committed. In states where cannabis is legal however, that’s no longer true. Police officers and business leaders in those states must instead show that an individual was actively impaired in order for a crime or policy violation to have been committed.
If you’re being tested for impairment by the police, the most important thing to know is that there is no amount of THC that has been correlated to a predictable level of impairment. Said another way, there is no scientific basis for being charged with impaired driving based on a THC test. The only valid ways to detect active marijuana impairment are a Drug Recognition Expert evaluation or a
Some states have attempted to instate “per se” limits for the amount of THC that can be in the body before someone is considered impaired. These are not based on any scientific evidence, and most states are reconsidering these laws.
For businesses, it’s even more challenging. They have no tool other than Gaize to defensibly detect active marijuana impairment.
Which type of test for Cannabis is best?
The answer to this question is entirely dependent on the reason for testing. In the following section, we’ll explore the use cases for each type of cannabis drug test, and the Gaize impairment test.
Urinalysis THC Screening: THC discoverable for 4-6 weeks since the last use.
Urinalysis drug screening uses urine from the test subject to detect the metabolic markers of drug use. This type of screening is commonly used in workplaces, though many states no longer allow for adverse action based on the presence of THC in the body. This testing is extremely invasive, often requiring test administrators to observe urine coming out of the genitals of test subjects. Urinalysis usually costs $80-$400 per test, depending on the substances being tested for, and results take several days to several weeks to be returned.
This study only lasted 30 days, but metabolites are still clearly and easily detectable at that time. Another study showed 46 days until the participants were below cutoff limits.
Blood THC Screening: THC usually discoverable for up to 7 days, though occasionally up to 4 weeks since the last use.
Blood THC tests are most often conducted by law enforcement. They are very accurate in determining the presence of drugs, including THC. These tests are also very expensive to conduct, costing several hundred to over $1000 per test. Blood tests must be captured by a specially trained phlebotomist, and results can take days or weeks to be returned. This testing is typically only conducted when a crime is suspected, like driving while impaired. Importantly, there is no scientific backing for testing some amount of THC in the blood and correlating that with impairment.
Note: While most cannabis users will not have detectable THC in their blood by 7 days since the last use, in several studies, there have been much longer detections of THC in blood. In this study, 11 participants had detectable THC for 26 days and one participant had THC still detectable in blood for 33 days. These results were confirmed by this study.
Mouth Swab / Saliva / Oral Fluid THC Screening: THC usually discoverable for 24-48 hours, though occasionally up to 8 days since the last use.
Oral fluid, also known as Saliva can contain THC from marijuana use. These THC tests use a mouth swab to collect saliva, which is then analyzed by either a machine, or a chemical assay to detect active THC. They are used by both law enforcement and commercial entities, with law enforcement usually using machines like the Draeger Drugtest 5000 or the Abbott SoToxa machines. Commercial entities usually use simple dip sticks that detect the chemical in the oral fluid.
Unfortunately, these tests are not selective to THC vs. CBD, and are therefore fraught with problems. Saliva THC tests are notorious for having high rates of false positives and for that reason are typically followed up with a blood test. The advantage to saliva THC tests is that they can be conducted quickly with results in around 10 minutes. Like blood tests, there is no amount of THC in saliva that scientists have ever correlated with impairment.
Of note, one study found that THC was detectable in oral fluid for up to 8 days after the last use. This is much longer than normal and results are highly variable. It does look like reliable detection is confined to 24-48 hours though. The accuracy of mouth swab oral fluid testing devices is notoriously poor, with false positive rates around 15%.
Breath THC Screening / THC Breathalyzer: THC discoverable for 2-3 hours since the last use. Only works for smoked cannabis.
THC breathalyzers are an emerging technology that test breath samples for minute traces of THC. These tests are extremely sensitive and extremely expensive. They are unproven but likely to become useful in jurisdictions where cannabis is still illegal. In those places, the presence of THC in the breath would constitute a crime. In places where THC is legal, marijuana breathalyzers are not useful. This is because no amount of THC in the breath has ever been correlated with a predictable level of impairment. Marijuana breathalyzers also only work for smoked marijuana, meaning that users of edibles are not detected, and it’s unclear if these work for vaped THC. The test results are very quick however, with most samples being evaluated in just a few minutes.
Hair Follicle THC Screening: THC discoverable for up to 3 months since the last use.
Hair follicle tests are typically only used by employers. They cost several hundred dollars to run and results typically take one to two weeks to be available. While less invasive that urinalysis, hair follicle tests have a high rate of false positives. Hair follicle tests can detect THC for an extremely long time - up to three months since the last use. In places where cannabis is legal, employers are typically not allowed to take adverse action against an employee for the simple presence of THC in their body.
Eye Movement Test / Gaize Impairment Screening: Tests for impaired eye movement, not the presence of THC. Impairment is discoverable during the experienced impairment only.
Gaize is an eye movement test for cannabis impairment. It works by putting the test subject through a controlled and automated test that requires test subjects to track a stimulus in a VR headset. This test looks for involuntary micro-movements of the eye and pupil reflex reactions that are consistent with cannabis impairment. Using advanced statistical and machine learning algorithms to analyze the data in real-time, Gaize is able to extremely accurately determine active cannabis impairment. This product is the only way to detect cannabis impairment in real-time with a portable, non-invasive testing process. Results are available in just 6 minutes, allowing for high throughput of test subjects.
You can learn more about Gaize by clicking here.
Impairment or presence of THC?
Driving under the influence of drugs (DUID) is a growing factor in impaired-driving accidents. Similarly, incidents of on-the-job impairment is increasing, and business owners are extremely concerned. With full legalization of marijuana on the horizon for the United States, and legal access to marijuana available in most states, knowing how long you can test positive for marijuana on a drug test is crucial information. Unlike alcohol, drug impairment testing is challenging due to the lack of a universal “limit” to determine impairment and the lack of current drug-detecting technology.
Here’s what you need to know about marijuana, the history of drug testing, THC, testing positive for marijuana on a drug test, and marijuana laws in the United States.
Haven’t smoked in weeks or months and still testing positive for THC?
That’s not surprising, unfortunately. THC and THC metabolite tests are very sensitive and these chemicals have a very long half life in the body. Drug testing services companies are very familiar with this phenomenon and the responsible ones will commonly warn employers about it. The bottom line though is that marijuana users can easily fail a saliva / oral fluid test for 48 hours following their last use of the drug. One study found THC in oral fluid for 8 days following the last use. That’s shocking - active THC in the saliva for over a week completely blows the idea that these are recent use tests out of the water. Urinalysis tests can be positive for much longer still. It’s not uncommon for these tests to be positive for at least 60 days, and sometimes as long as 4 months following last use. This is why it’s critical to use impairment detection technology in order to provide fairness to safe and legal THC users.
History of Drug Testing
Drug testing got common in 1971, ordered by President Richard Nixon shortly after the Vietnam War. The idea was for the military to start a urine drug testing program. The new program resulted in a very high drug positivity rate among returning military personnel which led to the Department of Defense defining drug testing requirements. The Army, Navy, and Air Force then established groups of active duty scientists for the development and implementation of drug testing procedures.
Thanks to the popularization of drug testing in the military, Quest Diagnostics began performing employer drug tests in the mid-1980s, and released the first Drug Testing Index (DTI) shortly after. This index examined positivity rates to provide an analysis of drug-use trends. In January 1988, the first DTI was published and it resulted in a drug test positivity rate of 13.6%. During the same year, both the Drug-Free Workplace Act and the Anti-Drug Abuse Act were passed by Congress. This was following several drug and alcohol-related accidents, the worst being a fatal train accident with the operator testing positive for marijuana.
The federally-mandated drug testing, along with a growing number of testing providers lead to testing among private sector employees. State regulatory agencies established guidelines for testing because of the increased awareness of drug testing. The Omnibus Transportation Employee Drug Testing Act was passed in 1991, which required the U.S. Department of Transportation (DOT) to test its applicants and employees. This was the first mandated testing required by law. It required trucking, aviation, railroads, mass transit, pipelines, and other transportation industries to test their candidates and employees for alcohol and drugs.
The Substance Abuse and Mental Health Services Administration (SAMHSA) was established to help implement the act in 1992. Its mission was to reduce substance abuse and mental illness in U.S. communities. Over time, the SAMHSA-5 has evolved to include marijuana, cocaine metabolites, amphetamines, opioids, and phencyclidine. The DOT guidelines require all drug testing to be lab-based and to include marijuana. This was the foundation for today’s drug testing, meant to prevent impairment in the workplace. SAMHSA-5 led to “zero-tolerance” policies which worked when marijuana and all other Schedule I drugs were illegal to use.
When the first U.S. states legalized marijuana for recreational use in 2012, the zero-tolerance approach started to become ineffective as the record low positivity rates of marijuana between 2010-2012 at 3.5% rose to a 16-year high in 2019. In most US states, and many other countries around the world, testing positive for THC can’t prove illegal or inappropriate behavior in today’s workplace.
Background on THC and Drug Tests
Delta-9-tetrahydrocannabinol (THC) is the main mind-altering chemical in marijuana responsible for most intoxicating effects. The duration that marijuana (THC) remains in a person’s system varies depending upon several factors, including: the amount of THC in the marijuana used, frequency of use, hydration of the person, metabolism of the person, the sensitivity of the drug test, and how much body fat a person has. Each of these factors can impact the period of time that THC is present in the body, and therefore all have an impact on drug test results.
Importantly, THC is lipophilic, meaning that it readily binds to fat in the body and is then slowly re-released into the bloodstream over time. The THC that gets released by fat in the body is non-psychoactive, meaning that it will not cause a “high” in the user. This THC is still what gets detected in drug tests though, which is why testing for THC in the body is not a reliable way to measure impairment. You can learn more about that in another of our blog posts, here.
Drug tests are used to screen for marijuana use, and to help detect drug use, impairment, intoxication, and/or an overdose. They are also used to monitor drug abuse as well as compliance with prescription drugs. Detectable amounts of THC may remain in the body for weeks after marijuana use. THC is usually detectable for up to a month in blood, 24-48 hours in saliva, 4 weeks or longer in urine depending on how often it is used, and up to 90 days in hair. In comparison, drugs such as alcohol may disappear in just a few hours and are metabolized linearly, matching experienced impairment.
THC is primarily broken down by the liver. The by-products created by the breakdown are then cleared through the urine. This is not the same for THC stored in body tissue, however, as it continuously gets released into the bloodstream over time. It repeats this cycle of getting broken down by the liver and cleared in urine until it has all depleted from the body. Metabolites (tetrahydrocannabinol carboxylic acid or THC-COOH) typically appear in urine within 60 minutes following a dose of THC but this process can take up to 4 hours. These metabolites appear in the urine for a period of time that’s dependent on frequency of use and other factors already discussed.
Where is Marijuana Legal?
Marijuana laws are some of the most controversial in the United States. The federal government classifies marijuana as a “schedule 1 narcotic,” meaning drugs that lack a currently accepted medical use while also having a high potential for abuse. Marijuana is “legal for adult recreational use” in some states and “decriminalized and/or made legal for medical use” in other states. The states where adult recreational use of marijuana is legal are Alaska, Arizona, California, Colorado, Connecticut, Washington D.C., Illinois, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nevada, New Jersey, New Mexico, New York, Oregon, Vermont, and Washington. The states where marijuana has been decriminalized are Nebraska and North Carolina. The states that have made marijuana legal for medical use are Alabama, Arkansas, Florida, Oklahoma, Pennsylvania, South Dakota, Utah, and West Virginia. The states that have both decriminalized and legalized cannabis for medical use are Delaware, Hawaii, Louisiana, Maryland, Minnesota, Mississippi, Missouri, New Hampshire, North Dakota, Ohio, and Rhode Island.
Workplace Drug and Impairment Testing
Today, there are four common times to drug test in a workplace: pre-employment, post-accident, at random, and for reasonable suspicion. Pre-employment is typically done after a job offer is made but before the new hire starts working. This type of testing is becoming much less common, particularly in states that have legal marijuana. The exception to that is for positions where safety or security is critical. Positions that include regulation or funding from the federal government also require pre-employment testing.
Post-accident is testing that’s required after an accident to determine if impairment could be to blame for the accident, especially one that causes injuries or fatalities. Random drug testing is when employees are selected at random for unannounced drug testing. Some employers still require this, though many are moving away from it unless absolutely necessary. Reasonable suspicion is when workers are showing signs of intoxication at work enough to cause an employer to be suspicious and test them.
Pre-employment is the most common screening method and most states allow this type of testing, however, some require employers to give notice to applicants. Pre-employment drug testing has been ruled by courts as not representing medical examinations under the Americans with Disabilities Act. The Equal Employment Opportunity Commission however states that such tests should be conducted after an offer of employment is made as the employer may need to ask about the candidate’s medical history. It is also easier to not hire someone who fails a drug test rather than fire an employee who is already trained and a part of the company. Businesses considered safety-sensitive may want to conduct ongoing screens after workers are hired, to make sure that employees driving or operating heavy equipment are deterred from using drugs.
The downside to cannabis screening in the workplace is that, in states where it is legal, it precludes an employee from using the substance responsibly in their off-time. This is like telling someone they can’t have a beer after work, and employees are starting to push back on these requirements. The primary concern is that all current marijuana tests are retroactive - that is, they only measure past use, not active impairment. This is why Gaize was started. Gaize conducts an automated version of the tests law enforcement already uses, and the uses machine learning to evaluate impairment.
Conclusion
Marijuana impairment is extremely complex and difficult to detect accurately. Classic drug tests look for THC in the body by evaluating a body fluid (blood or saliva), breath, or hair follicles. These tests are fine in places where cannabis is legal, or where you only care about past use and not current impairment. For those situations that require knowing if someone is currently impaired by marijuana, eye movement screening using Gaize is the most accurate test available.
