Medically Reviewed by
Jason Crawford

Article Last Updated on December 25, 2022

Drug testing or drug screening at work is a common practice in some countries in the world, especially in the United States. That is why a lot of people are curious about the detoxing period, particularly marijuana users since pot is one of the most commonly used drugs in the world.

Some companies perform this test as part of the pre-employment assessment, while others exercise their right to test their employees (through a blood test or urine drug test) once in a while to check their compliance with work ethics.

So, what if you run into a job advertisement you really want to apply to, but remember you smoked weed one week ago at your friend’s party? Will you test positive if you took a few pulls from a joint on your day off and your boss surprises you with a drug test a week later? What about if you smoked one bowl? How long does one bowl stay in your system?

In this article, we’ll answer these questions by looking into how long weed stays in the human body and the length of time during which marijuana is detectable in your system. But first, let’s find out how drug testing became a thing.

The Emergence of Drug Testing in the World

In the States, contemporary drug testing is a leftover from the politics of President Ronald Reagan and the War on Drugs in the 1980s. 

In 1988, Reagan signed an executive order that made drug testing compulsory for federal employees and some contractors. Corporations quickly followed suit and, by 1987, around 25% of the Fortune 500 companies in America had performed drug tests on their employees. 

Since then, drug testing in one form or the other has spread around the world.

The implementation of drug screening programs aimed to reduce drug use in general, but the evidence available shows little correlation between drug tests and reduced drug use. Moreover, there’s insufficient support for the assumption that recreational or medical cannabis use adversely affects employees’ productivity.

How Common Is Drug Testing in US Workplaces?

Drug testing for substance abuse is rather common in the US compared to other parts of the world. It’s often conducted as a pre-employment measure, and after you have received the job it can be done as random drug and alcohol screening, as part of the annual physical examination, or as a measure after an accident at work.

While regulations differ from state to state, according to the Analysis of Employer drug testing in the US, the top 5 industries that require pre-employment drug testing are:

  • Government;
  • Health-care and hospitals;
  • Manufacturing;
  • Automotive;
  • Transportation and Logistics.

Why Do I Have to Be Drug Tested at Work?

There are a few reasons why some employers insist on mandatory workplace drug testing, which include:

  • Identifying employees with drug problems. One of the main reasons why employers require drug tests during the pre-employment phase is to limit the chances of employing a person who engages in substance abuse. These employees often pose a risk to the productivity of the company, which is one of the highest values in the workplace for employers.
  • Protecting the business and the company. If an employee makes a mistake at work which harms the business and the company or the employers and customers, and is found to be under the influence of drugs, the company is liable. The company can be held accountable by the government as a result of the actions of the employee, which often results in lawsuits and trials which can taint the image of the company. Drug testing can prevent all this and promote the good reputation and professionalism of the company.
  • Maintaining the safety of other employees. Employees thrive in a healthy and productive work environment. In cases where an employee is under the influence of drugs, it often affects their productivity and overall performance in the workplace. As a result, workplace collaboration, morale, and productivity can suffer because the other employees won’t feel as motivated to do their best work. Drug abuse can also affect personal safety as well as the safety of others, which can also hold the company liable.

Has Drug Testing Deterred Marijuana Users?

While there is no definitive answer to this question, drug testing may deter users from drug abuse. Drug testing in the workplace may reduce the consumption of drugs because of a few reasons. First, employees are generally afraid of getting caught, next comes the probability of the punishment, and finally, the severity of the penalty, which can result in losing one’s job.

While different companies have different policies with regard to drug testing, generally they test employees in the following 4 situations:

  • Pre-employment. A drug screen is quite common before a new hire starts working, especially in government and military jobs.
  • Post-accident. Drug testing is quite common in the aftermath of a workplace accident, especially in cases where an accident has injuries or fatalities in order to determine whether drug use may have contributed to the accident.
  • At random times. In companies that have a drug-free workplace program, random and unannounced testing is quite common.
  • When there’s reasonable suspicion. If an employee comes to work showing signs of intoxication, like uncoordinated movement or slurred speech, a mandatory drug-test is often the first thing the employer orders.

Even though drug testing may not have eradicated drug use from the workplace, according to a 2020 systematic review of the effectiveness of employer‐led interventions for drug misuse, in some environments, employer-led interventions have proven to be effective.

How Does Your Body Process Weed?

The term weed is used for the recreational or medicinal drug that comes from different variants of the Cannabis plant. This plant consists of almost 500 bioactive compounds including groups like cannabinoids, terpenoids, flavonoids, and alkaloids (Bohini et al., 2018).

The most popular cannabinoids are Tetrahydrocannabinol (THC) and Cannabidiol (CBD). The former is the plant’s most psychoactive compound, shown to exhibit “pain-relief, appetite-stimulation, brain-health, antioxidant, anti-nausea, and antispasmodic properties” (McClements, 2020), while the latter is non-psychoactive and used for its medicinal properties, mainly anti-inflammatory properties and pain relief.

The way that your body processes weed compounds largely depends on your metabolic rate since our body disposes of the cannabinoids through metabolism. If you are a heavy user, it might take more time for your body to detox, so the frequency of use is also a key factor. Moreover, the individual’s lifestyle such as eating habits and level of exercise play a role too. 

Once they enter the bloodstream, cannabinoids are turned into metabolites by the liver’s metabolic enzymes. The fact that THC and CBD are lipid-soluble is why they are absorbed and stored in the fat cells. If you have a higher level of body fat (higher body mass index- BMI), your body will store more cannabinoids. 

How Long Does Weed Show Up in a Drug Test?

Marijuana use has been getting higher in recent years in the USA, and while some marijuana smokers do it recreationally, others use medical marijuana for certain health conditions. Regardless of whether you’re a regular smoker, or if the last time you smoked from a bong was 4 weeks ago, here is all you need to know about the type of drug tests that your employer can give you in order to test for substance abuse, and how long can weed show up in a drug test.

How long marijuana stays in your system depends on several factors:

  • The amount of weed consumed;
  • How often you use;
  • Your level of tolerance;
  • Your physical activity, metabolic rate, body mass index, and weight;
  • Your hydration levels;
  • If you have consumed weed on an empty stomach;
  • Other medical conditions you might have.

Depending on the amount of time that has passed before your last use, and the type of marijuana drug test you are taking, the test will show a positive result from four hours up to 90 days.

Today there are different drug tests which determine the concentration of THC in the body, but the most commonly used are the following:

  • Urine test
  • Blood test
  • Saliva test
  • Hair test
  • Home test

Urine Test

Urinalysis is the most common form of drug testing, especially in the workplace. Urine testing is a painless procedure done by taking a urine sample which is then tested for the presence of illegal drugs or prescription medication in the body. 

Heavy smokers on occasion opt for synthetic urine in order to cheat the test. Since this is illegal, we will provide you with information about how urine testing works so you can learn if your body has enough time to detox.

When testing for weed, the urine test contains immunoassays with antibodies that are sensitive to THC’s main metabolite 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH). The federal cutoff level for THC-COOH is 50 ng/mL, so if your result shows more than 50 ng/mL, it’s positive and you’ve failed the test. In this case, the first test is followed by a Gas Chromatography/Mass Spectrometry test to double-check the result with a lower cutoff level of 15 ng/mL.

How Long Will THC Stay in Your Urine if You’re a Regular User?

So if you were wondering how long does weed stay in your system, we have your answer but it’s not as straightforward as you might have expected it to be… A study conducted by Mayo Clinic Proceedings in 2017 gave the following marijuana detection window based on how frequently the participants consumed the drug:

  • Occasional Use (Less than 3 times a week): 3 days
  • Moderate Use (3-4 times a week): 5-7 days
  • Chronic User (Once a day): 10-15 days
  • Heavy Chronic Users (Several Times a Day): 30+ days

Another study shows that if you’re a nonuser, after a single weed exposure, the urinary amount of THC metabolite is detectable for only 72 hours

A third study published in Experimental and Clinical Psychopharmacology back in 2000, tried to identify the detection window for chronic weed smokers, i.e individuals who’ve smoked weed more than 5,000 times. 

There were 17 participants who abstained from smoking weed for a month. The study gave some interesting results:

  • 6 participants: passed the urine test after 30 days.
  • 5 participants: after one week.
  • 4 participants: after two weeks.
  • 2 participants: after three weeks. 

Blood Test

A blood test conducted to check for drug use is done by drawing blood and testing it to detect any presence of certain drugs and opiates. Unlike the other testing methods, blood tests are invasive and more difficult to administer. Additionally, because the window for testing blood is the smallest, this type of test is used less frequently.

With a blood test, your drug test results will be positive from 4 hours up to 24 hours after you have consumed weed, depending on the quantity consumed. Although, if you’re a frequent user, weed can show up on your blood test for up to a week.

Saliva Test

Oral fluid testing is one of the newest and less invasive forms of drug testing compared to urinalysis. It is done by taking a swab of saliva and testing it for the presence of drugs and opiates. It is less easily tainted compared to urinalysis although it’s more expensive.

Weed can be detected in the saliva for up to 72 hours from the time you consumed it.

Hair Test

The hair follicle test is gradually becoming a more common way to test for drug use in the USA. Its biggest advantage is that it gives the biggest window for detecting drug presence in the body. It can be done by either using hair from the head or body hair.

This kind of test has the highest length of detection period since weed and other drugs can be detected for up to 3 months.

Home test

A drug screen can even be done in your own home. It’s a great way to double-check if you will be detoxed before undergoing a test at work, or to test your kid for substance abuse.

An at-home THC test is most often a urine test which gives you a clear result in about 5 minutes depending on the test you take. The tests are similar to those that laboratories use to test for drugs. The test results can come out positive, negative, or invalid, in which case you need to take another test.

If I Smoke Once, Will It Show Up?

If you take a look at an article we’ve done on this subject titled How long does smoking weed once stay in your system, you’ll find out that this answer is different depending on the type of drug test you’ll be asked to take, but also how frequently you consume drugs. Meaning the detection time frame isn’t the same for first-time users as it is for daily users, and also, the results aren’t the same when taking a blood test, compared to doing the hair follicle test.

Regular and daily users have higher chances of getting a positive drug test since their body will need a longer time to detox from weed, while first-time users or users who hardly ever smoke weed will detox faster and probably get a negative result if they get tested using saliva, blood, or urine drug tests. Since the hair follicle drug test detects cannabis consumption for up to three months, both groups may end up with positive results.

How Long Does One Bowl Stay In Your System?

While the time frame for cannabis detection can vary based on the user’s tolerance level, how much they’ve consumed, their hydration levels, metabolic rate, and other factors, the average detection time is as follows:

  • Urine screen (has a 72-hour period for detecting THC metabolites for one-time users, while chronic users can test positive for up to a week);
  • Blood screen (infrequent users can get a positive result from 4 to 24 hours after using weed, and frequent users can get a positive test result for up to a week);
  • Saliva test (occasional users can expect to get a positive test result for up to 3 days, while heavy users can end up with a positive test result for up to 29 days);
  • Hair test (while this test offers the biggest detection window of up to 3 months, this is the least done test since it’s the most expensive one).

What Helps the Body Detox Marijuana?

Cannabis users often ask how they can decrease the levels of THC before taking a drug test. Depending on the period of time since you last smoked marijuana and how often you use it, there are some methods that can help you flush your body from the weed faster. 

Frequent users will need more time for their bodies to go back to normal compared to occasional users. And while using some prescription medication can result in a false positive on your test, this is rarely the case in weed testing (it’s more common when testing for other drugs). 

There are different ways you can help your body go back to normal after consuming marijuana. The most common advice is to consume a lot of water. Some sources go as far as saying that lemon juice and cranberry juice can help you, although this hasn’t been proven. The same goes for using a niacin detox (vitamin B3), as a recent study done by the Greater Baltimore Medical Center has shown, that dosing with high levels of niacin can result in tachycardia, flushing, skin rash, and vomiting, but not detoxing.

Apart from detox kits that contain detox drinks, some sources suggest doing exercise or fasting to reduce THC levels in the blood. To counter that misconception, a study done in 2014 by the Department of Clinical Pharmacology in Norway shows that neither food deprivation, nor physical exercise helps to release fat-stored cannabinoids faster.

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So, the answer to the question “Will I pass a drug test if I smoked weed one week ago?” is yes, there’s a decent chance you’ll pass the drug test but only if you’re an infrequent or first-time weed smoker. If you’re in good physical shape and have a high metabolic rate, the chances to pass the test are even higher.

If you smoke weed regularly, i.e. almost every single day, there’s a higher risk you’ll fail the test if you take it only one week after you stop smoking. For chronic users, the chances of passing the test in that timeframe are next to impossible.

Additional Sources

Bonini, S. A., Premoli, M., Tambaro, S., Kumar, A., Maccarinelli, G., Memo, M., & Mastinu, A. (2018). Cannabis sativa: A comprehensive ethnopharmacological review of a medicinal plant with a long history. Journal of Ethnopharmacology. doi:10.1016/j.jep.2018.09.004

McClements, D. J. (2020). Enhancing Efficacy, Performance, and Reliability of Cannabis Edibles: Insights from Lipid Bioavailability Studies. Annual Review of Food Science and Technology, 11(1). doi:10.1146/annurev-food-032519-051834

A passionate advocate for the benefits of cannabis. Fraser Horton, who has a background in botany and a strong love of nature, has spent years researching how cannabis affects the body and mind. He established Leaf Nation in 2020, where he has devoted himself to educating people about the legalisation of marijuana and its safe and responsible use. Fraser is committed to highlighting cannabis’ potential for improving wellness and working to dispel the stigma associated with its use.


The information presented on this page is provided as a public service to aid in education and is derived from sources believed to be reliable. Readers are responsible for making their own assessment of the topics discussed here. In no event shall Leaf Nation be held reliable for any injury, loss or damage that could happen if using or abusing drugs.