How to Pass a Drug Test After Smoking Weed

NuggMD Team
July 27, 2021

The information is provided for informational purposes only and does not relieve readers of their obligation to obtain qualified medical, legal or other professional advice.

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There are quite a few methods to pass a drug test, but which ones work?

For the modern-day cannabis user, the infamous “drug test” can pose a daunting challenge. The truth is, company-sponsored drug tests can force you to make difficult decisions about your health and/or career. Unfortunately, many private corporations and most federal organizations still test for marijuana even in the face of convincing research showing that marijuana use reduces opiate use.

Sadly, this is a reality for both recreational users and medical users in many states. Even the few states that have passed workplace protections for cannabis patients still allow marijuana drug testing for parolees, federal workers and certain job categories. Passing a planned drug test is simple; just stop using marijuana for a long enough to eliminate the remaining traces of THC.

Before we get into the nitty-gritty, understand that the methods of passing a drug test listed below have successfully been used in the past by some, BUT the only sure method of passing a drug test is abstinence

How Long Does Weed Stay In Your Body?

While studies have provided some insight on how long THC stays in the system, the topic’s largely still debated. The National Drug Court Institute estimates that detection times can last from 4 days to more than two months! But on average, occasional users can be detected up to 4 days after use and frequent users can be detected for more than a week.

Despite the estimated detection periods provided above, you usually aren’t given the option to delay your drug test. Not surprising, right? So, let's take a look at the types of drug tests we face, and methods that are commonly used to pass them.  

On average, occasional cannabis use can be detected for up to 4 days after use.

What Types Of Drug Tests Are There?

Believe it or not, urine isn't the only way to detect cannabis in your system. The time parameters for detection quoted above are for urine, but hair, blood and saliva tests can also detect THC and new tests are being developed that can detect cannabis in the breath. Let's review the basics.

Urine Tests For Marijuana

Urine tests are the most commonly used drug tests worldwide. THC can be detected for more than two months in urine in extreme cases. For most casual users, THC can be detected in urine for a couple of weeks after consumption. 

Urine tests are the most common method of testing for marijuana use.

How Does A Urine Drug Test Work?

Marijuana urine tests detect delta9-THC-OOH when it's excreted in your urine after consuming marijuana. Urine drug tests use a dip stick that is saturated with an antibody that reacts with the THC. The dipstick is inserted into the urine specimen. The urine moves up the dipstick through absorption (capillary action), and if there is any THC present in the urine, the antibody on the dipstick changes color.

Most urine drug tests are set to a sensitivity level of 50ng/mL, although some tests can be more sensitive. A urine drug test usually requires at least 30mL/ of urine. Urine drug tests are more than 99% accurate, so there's little hope of fooling this test if you have a detectable amount of THC in your urine.

How To Pass A Urine Test For Marijuana

Again, the only guaranteed way to beat a urine drug test is to abstain. If your livelihood or freedom depends on a clean urine drug test, don't use marijuana. If you find yourself in a pickle because you didn't follow this advice, there are methods you can try, but nothing is guaranteed.

drug test results
The only fool-proof method for passing a drug test is abstinence.


The most common method used to beat a drug test is to dilute the urine. This is done by increasing fluid intake to the point of frequent urination. First morning urine samples are avoided because the metabolites will build up in the urine overnight. 

Proponents of this method usually load up on B vitamins while pushing fluids because B vitamins color the urine, giving it a less diluted appearance. This won't make a difference with a high-quality lab test that measures the specific gravity of urine to check for dilution, but it does help with simple dipstick tests that rely on visual confirmation only. 

many people try to drink water to dilute canabis naturally
Dilution is the most common way to try to beat a drug test for marijuana.

If a lab does reject a sample because it's too diluted, they usually provide a second chance to provide a new sample, so you shouldn't use any cannabis before you get the results of the test.

Aside from the risk of failing a drug test, there are health risks to pushing large amounts of fluids or taking diuretics to increase urine output. Believe it or not, you can actually overdose on water. This is called water intoxication and it's fatal if untreated because it disrupts the metabolites that keep your heart beating.

A healthy adult can flush out about 20 liters of water per day, but only at a rate of about 1 liter per hour. Therefore, drinking any more than a liter of water per hour can become dangerous, and even more so for young or older people whose kidneys are less efficient. So, no brainer, talk to your doctor before pushing fluids or taking diuretics, especially if you have any health conditions that can affect metabolite levels. 


Adultering urine involves putting bleach, vinegar, baking soda or other substances in your urine after it's in the cup. First, this is very difficult to do with a direct observation test. Second, it's not a very reliable method. 

Some test-takers will sneak in a vial of adulterant to throw off a drug test, but these are usually detectable.

EMIT drug tests are sometimes thrown off by a few drops of Visine. Some testees try to use bleach, detergent, salt or glutaraldehyde (a cleaning solution), but these substances are usually detected by visual inspection or smell. 

Klear and Whizzies are commercial adulterants that are harder to detect, but still detectable by a good lab. Also, they aren't 100% reliable and they don't help at all for those who are forced to urinate as someone watches--barbaric, we know.

In addition, major labs like Quest Diagnostics have figured out how to detect the most common adulterants in urine. They even have a chart of common adulterants used to cheat drug tests that they can detect. 

This leaves those in truly dire situations considering a more drastic option -- substitution.


In truly desperate situations, cannabis users have rigged themselves up with bags containing clean urine. IF they are allowed to urinate in privacy, they can then substitute the clean urine for their own. Some companies even sell dehydrated urine and synthetic urine to be used for this very purpose. 

There are a couple of major problems with this method. 1) Drug testers usually observe a person's body before they are allowed to provide their sample. Yes, it's creepy, and it's also a very effective way to tell if someone is wearing a rig. 2) The samples are almost always tested for temperature. This is a very easy way to tell if you're providing your own urine or not. That being said, there are ways to warm the urine first. The Whizzinator has several models that are designed to be warmed against your skin. They also sell synthetic urine. 

Hair Follicle Drug Tests For Marijuana

Hair tests suck. Hair follicle tests have been shown to have racially biased results because marijuana is more easily detected in thick dark hair than thin light hair. There's no way around this one other than shaving every single inch of hair on your body including your eyebrows. If you show up to a drug test in this condition without a medical explanation, you're probably going to be presumed to be using drugs. And you'll look weird too.

Hair drug tests usually require about 100 to 120 hairs from the crown of the head.

The test is performed by collecting between 100 and 120 hairs from the crown of your head. For those with little or no hair, they can be collected from any part of your body.  The hair is then sent to a lab. The test will detect drug use over the past 90 days, but it can't determine exactly when the drug use occurred because everyone's hair grows at a different rate. It is possible to have a false-positive result. It's also possible for a hair test to detect one-time drug use if the use was long enough ago for the hair to grow out and show it--usually about a week. 

How to Pass a Hair Follicle Drug Test

The best way to pass a hair follicle drug test is to stop using it for several months and then get a nice hair cut so the only hair on your head is clean hair. This obviously isn't an option for a test on short notice. 

If you're truly desperate, Neutrogena, Head & Shoulders (Fine/Oily), and Rave have been shown to cause lower drug concentrations in hair than Pert or Prell. There are also commercial shampoos designed to rid the hair of drug traces like Toxin Rid, but they're incredibly expensive and not guaranteed to work. 

Some have better success using Toxin Rid with the Macujo Method, which is a specific way of washing the hair with several different products to eliminate traces of THC in the hair and scalp:

  • Wash and rinse hair, then add vinegar and work it around on the scalp.
  • Then work Clean and Clear through the scalp.
  • Put on a shower cap and let the chemicals work for half an hour.
  • Shampoo hair twice with Toxin.
  • Wash hair with a tiny amount of Tide.
  • Shampoo hair again with Zydot Ultra Clean
  • Repeat the process 3 times a day before the test and once more the morning of the test.

Obviously, this method would be very hard on the hair and it could also result in scalp irritation, allergic reactions and even hair loss!  

Some have reported success passing a THC drug screen with special hair cleansers.

Understand that hair drug tests aren't as sensitive for cannabis as other methods. In fact, hair follicle drug tests can be so inaccurate that family courts in many states don't even allow them! If you're facing one of these tests, your better alternative may be a lawyer.

Blood Test For THC

On rare occasions, such as for a traffic accident, highly sensitive security job or court-sanctioned testing, a person may have a blood test for marijuana. It's a simple test that only requires a small vial of blood, but it's invasive and as with any blood draw, it does carry a small risk of infection or bruising, so blood tests are not commonly used to detect cannabis. 

Blood tests are pretty air tight. They're accurate down to the nanogram. Chances are, if you're taking a blood test for drugs, it's due to an accident or other run-in with the law. That means you won't have time to plan for it. Luckily, blood tests for casual marijuana use only detect THC for 1 or 7 days after consuming. Those who smoke more often, or consume large amounts of edibles can show THC in their blood for several weeks

Blood tests for marijuana aren't very common.

It has to do with how our bodies process and store cannabinoids. When we metabolize THC, we create a byproduct called THC-COOH which is the primary substance tested for when testing for cannabis use. This substance is easily absorbed by fat cells and stored, and fat cells can store cannabis for weeks or even months! This is why cannabis is detectable for longer than any other drug.

As we naturally burn fat, we release the THC back into our bloodstream for filtration and removal from the body. Even simple activities like exercise can cause these metabolites to transfer from our fatty tissues back into our bloodstream. This doesn't mean you're actually getting high from these small releases. It just means that it's detectable. It's unknown whether any impairment accompanies these small releases of THC from your fat cells, but anecdotal evidence seems to indicate that it doesn't. 

Still, studies about THC metabolism can give us insight into how we can reduce the possibility of THC showing up in blood after abstinence. A 2009 study repeatedly injected rats with THC for 10 days. They then induced lipolysis, which is the process where your body breaks down fat cells, either by injecting ACTH or depriving the rats of food for 24 hours. They then measured THC levels in the blood. Lipolysis increased the amount of THC in the blood

So, whether THC is detectable in your blood depends on how much fat you have, how quickly your body metabolized THC, how much you consume, how much you exercise and even how much you eat. 

How To Pass A Blood Drug Test

There are only two ways to pass a blood drug test: detox or abstain. There is nothing you can eat, drink or use to clean your blood of cannabis.

Naturally detoxing (aka, abstinence) can take between 30 and 60 days to completely eliminate all traces of cannabis in your system, and up to 90 days if you're a very heavy user with ample fat cells for storage of THC-COOH. Most people who have fair warning to detox will:

  • eat a very clean diet (veggies, veggies, and MORE veggies), 
  • drink plenty of water (NOT sugary drinks because they increase FAT!), 
  • exercise to work up a good sweat daily,  
  • try to lose a few pounds if they are heavy, and then
  • eat well in the days leading up to the test to avoid lipolysis.

But detoxers are careful not to lose too much weight when detoxing because this could actually slow down the body's metabolism to the point that it slows down THC elimination. The main focus is on having the healthiest nutritional input possible, exercising to work up a sweat and increase metabolism, and drinking plenty of healthy, non-sugary fluids.

Exercising might help speed up metabolism and clearance of THC from fat cells.

Sadly, there isn't a way to clean the blood of THC on short notice. In these cases, a person might be tempted to try detox aids to speed up metabolism, but these tend to work by diluting your urine and increasing your urine output. You can't dilute your blood. They don't work for blood tests at all.

So, naturally detoxing and abstinence are your only effective ways to detox from THC for a blood test. Luckily, blood tests for THC aren't that common.

Mouth Swab Drug Test For THC

Mouth swabs, aka oral fluid or saliva drug tests have the second  shortest window of detection times from ingestion and are only up to about 98% accurate. Most tests can only show cannabis use within the past 24 hours, although in rare cases THC can be detected for up to a week. The short testing window, in addition to the lack of invasiveness (unlike urine and blood tests), makes saliva drug tests an increasingly popular option for both testers and testees.

Saliva tests for marijuana are becoming increasingly popular due to their shorter detection window.

Oral marijuana tests work by detecting delta-9 THC in your saliva, as opposed to other tests which detect metabolites like THC-COOH. When THC is eaten or smoked, some small amount of it remains in the lining of your mouth and is slowly released into your saliva for up to 24 hours. There are several different test designs. Some involve spitting a small amount of saliva into a tube, while others use a cotton swab to collect saliva from your mouth. The tester is usually involved in collection of the sample, so it's difficult or impossible to tamper with this type of test.

How To Pass A Mouth Swab Test For THC

Unless you're facing a surprise test on the roadside, it's pretty easy to detox for one of these tests. In fact, it's a great time to simply take a weed tolerance break. A tolerance break is where a cannabis user stops using cannabis for a short period of time in order to return cannabinoid receptors to their normal levels. This usually takes a week or two, but some studies show it can take up to a month for heavy users. What better time for a t-break than when one is about to take a drug test?

If you're in a pinch and have the opportunity, some find that it can help to clean the heck out of your mouth before providing a sample. They will brush thoroughly, using a waterpik or floss if possible to get between gums and teeth. Rinsing repeatedly seems to help. Some have found that heavy rinsing with mouthwash or hydrogen peroxide is also helpful in a time pinch. NEVER SWALLOW HYDROGEN PEROXIDE OR MOUTHWASH. Diluted hydrogen peroxide rinses are often preferred because they won't lead to false positive alcohol tests like mouthwash does.

Cleaning the mouth very thoroughly might help pass an oral drug test.

Keep in mind that an antiseptic rinse only alters your saliva for up to 30 minutes. It's also not a foolproof method. Like all other methods here, it's still very possible to fail your drug test. This is more of a desperate hail mary. You're better off just avoiding situations where you would be forced to submit to such a test while high on short notice. In other words, don't drive or operate heavy machinery while high.

Breath Test For THC

Breath tests for THC are a brand new technology. They detect THC in your breath much the same way alcohol is detected with a breathalyzer. These tests have the shortest detection time for marijuana consumption and are therefore much less likely to yield false-positive results for intoxication. Since marijuana breathalyzers are so new and therefore of unknown reliability, they are still very rare but may become more popular in the near future.

Breath tests for THC are beginning mass production in 2021.

Hound Labs has created a THC breathalyzer that they say can only detect THC use within the past four hours, which allows them to differentiate "between the person who smoked cannabis legally and responsibly at a BBQ on Friday night, versus their colleague who smoked Monday morning on the way to work." The tests are set to be commercially available in Spring/Summer of 2021 with mass production ramping up throughout the year.

However, they don't seem to be able to accurately detect edible consumption. So, if you see these tests in the near future, they may be used in conjunction with saliva tests. They're also, as-yet, unproven in the field; so should you fail one of these tests on the road or at work, a legal challenge should be possible with a very good lawyer. Court approval is required to use these tests as evidence for arrests.

The Takeaway

In summary:

  • Urine tests can show cannabis use from a few days to several weeks.
  • Hair follicle drug tests can show cannabis use for up to 90 days.
  • Blood tests can show cannabis use for between a few days to several weeks.
  • Saliva tests have the shortest current detection window, from 24 hours to a week.
  • Breathalizers may be able to cut that detection time to 3 or 4 hours in the near future.

In all cases, casual users are much less likely to have a false positive test for impairment, while heavy users who are overweight are most likely to have a false positive test for impairment.

The inaccuracy of THC testing leaves plenty of room for legal challenges in the case of a positive test, but positive tests can and will still cost you. So, the safest and most effective way to pass a drug test for marijuana will always be abstinence. This is the only good advice to give a person who is facing a drug test. Anyone who tells you otherwise is probably trying to sell you a product that has an unproven success record or doesn't work at all.

Your freedom isn't worth risking. So, never drive while high. Never use cannabis if doing so could endanger your freedom, for instance if you're on parole and not approved to use it medically. Note that mere physician approval won't protect most parolees. They must get permission from the parole board or a court order to be legally protected. And never use cannabis if your job, child custody, or any other aspect of your life could be endangered by detection of your use. It's simply not worth the risk considering the highly likely outcome of a positive test. 

Unfortunately, this is the world we live in for now; but attitudes toward cannabis are changing, and we're likely to see testing for past cannabis use end in the future as tests that detect actual impairment become available.

NuggMD Team
NuggMD is the nation's leading medical cannabis technology platform, facilitating access to medical marijuana for patients in California, Nevada, New York, Oklahoma, Pennsylvania, Ohio, Missouri and now New Jersey. NuggMD's patients receive their evaluations entirely online via face-to-face video chats with licensed doctors from the comfort and privacy of their own home.

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