Fraser Horton
Fraser Horton
Last Updated on October 1, 2020

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?

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 Australia Work Places?

Compared to the USA, drug testing for substance abuse is less common in Australia, both before the employee gets the job and during the course of the employment. 

According to Practical Law, in Australia, employers have the right to require drug testing but it’s primarily used in safety-critical areas such as transport, energy generation, and more recently, in the construction industry. It’s typically done if there’s an “express obligation” and in agreement with the employee.

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?

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 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 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.

Home tests are often urine tests, and they give 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.

What Helps the Body Detox Marijuana?

Cannabis users often ask how they can decrease the levels of THC before taking a 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). 

So let’s find out how you can help your body flush the weed out faster.

There are different ways you can help your body go back to normal after consuming marijuana. The most common advice is consuming 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 niacin (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.


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


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