Medically Reviewed by
Jason Crawford

Article Last Updated on January 10, 2023

If your workplace is subject to frequent drug screening or you’ve applied for a job that requires you to take a drug test, you must be looking for some ways to flush the weed out of your system. Many marijuana users face the same problem in states where cannabis consumption is not legalized yet, or if their employer has a strict policy against marijuana use.

Sometimes, you have weeks to prepare and simple abstention may be enough, but other times you may not have enough time. You may be caught off guard which may cause you to test positive on a drug test and put stress on your job. These situations are especially unfavorable for individuals who use weed for medical reasons as it’s harder for them to abstain from their medicine.

Whatever the case, you might be looking for some tips on how to pass through a drug screening, which is what we’ll cover in this post. Please note, however, that we are not condoning cheating on drug tests or trying to beat the system. This article is purely for informational purposes only.

Drug Tests Are Designed to Detect THC Metabolites

THC (tetrahydrocannabinol) is the main mind-altering active ingredient in weed that causes feelings of elation, also known as “the high.” Unlike the other primary cannabinoid present in marijuana, CBD (cannabidiol) which is not psychoactive, THC temporarily alters the functions of your mind and your body.

The most common effects caused by THC are feelings of euphoria and relaxation, altered perception of time, deep relaxation, feelings of bliss, heightened creativity, and often impaired body coordination.

How THC Behaves in the Body

When a certain amount of THC enters your bloodstream it’s able to travel through different parts of your body and influence various bodily functions, which is why weed is often used as medical marijuana.

After a few hours, when the effects start to subside, the body starts breaking THC down into smaller byproducts, also called metabolites. This process goes on in the liver where over 80 metabolites of THC are produced and subsequently stored in the fat cells of the body because THC is a fat-soluble molecule.

From here, the metabolites are gradually eliminated by the body fat mostly through sweat and urine. THC metabolites may live snuggly in the fat cells of people who are regular users of marijuana and accumulate there over time, making it harder to eliminate shortly before a scheduled drug screening.

Drug tests are designed to detect one THC metabolite and it’s called THC-COOH, which is the most abundant metabolite and easily detected. Depending on factors like frequency of use and strain, different types of drug tests can detect its presence over different periods.

Types of Drug Tests

Different drug tests have different detection windows, meaning that some may detect the use of weed for longer periods than others. Let’s see what they are:

  • Blood test – not the most commonly used test, but fairly accurate. It can detect traces of THC metabolites for up to about 36 hours after last use;
  • Urine test – by far the most commonly and widely used test for years because of its accuracy and practicality. Urinalysis has different detection times depending on how often marijuana is used, where for infrequent cannabis use the detection period is shorter (1-3 days or a week) and for heavy users, it’s much longer (up to 21 days depending on frequency);
  • Saliva test – not a very common marijuana drug test and most relevant after smoking marijuana. It can detect THC up to two days after smoking;
  • Hair test – the most accurate and can detect drug use for the longest period of time. It can detect levels of THC in the hair follicle for up to 90 days of previous use and it’s most reliable for the detection of chronic cannabis users and long-term substance abuse.

How to Eliminate THC from Your System Before Drug Testing

Normally, it would take about 30 days of abstaining from using weed for your body to flush out all traces of cannabinoids and THC metabolites. However, sometimes you need to do a drug screening sooner than that so you’ll have to speed up the process a little bit.

Every drug test has a cutoff level at which THC is detectable, so if you can’t flush out the THC completely, you should at least try to get it below this threshold. Let’s see what you can do to avoid getting positive results if you need to take a blood or a urine drug test soon.

Natural Detox

If you have enough time, the best and safest way is to allow your body to take care of the excess THC metabolites on its own while you temporarily abstain from weed use. If you’re a casual weed user, your body probably hasn’t accumulated large amounts of THC and it will take less time to flush it out.

You can also alter your diet a little bit and increase the intake of fiber and green leafy veggies, and include some mild to moderate exercise.

Hydrate, Hydrate, Hydrate

The classic method for detoxing your system from THC or any substance is drinking enough water. You need to properly hydrate yourself anyway, but when you have an upcoming urinalysis you’ll want to up your water intake just a little bit more.

However, you’ll have to be careful not to overdo it, as when urine is overly diluted, it could arouse suspicion and cause impairments on the test, meaning you’ll probably have to retake it.

Generally, it’s recommended to drink about 3 gallons of water a day and pee as much as you can, but don’t force your water intake, because overburdening your system with fluids is definitely not recommended.

Take Vitamin B12 or Niacin

Speaking of diluting urine samples, some people take vitamin B12 because it helps to add the color back to the urine and make it look more natural and not as pale.

Other people also take niacin, which is a form of vitamin B3 as it’s considered to be able to help the body flush out the THC metabolites sooner. However, niacin is better suited for occasional users and it’s not recommended for heavy users as it may cause side effects.

Use Natural Diuretics

Natural diuretics that make you pee more often and flush out the water in your body can help. Tea, coffee, and cranberry juice are well-known products that can aid the natural detoxification process and help you get negative test results.

You can also try some over-the-counter diuretics if you feel like they would be more helpful in your particular case, but don’t try anything stronger as you don’t want to mess with your body’s natural process.

Do Detox Kits Work?

Nowadays there are many detox kits and detox products, none of which have been FDA approved and their efficacy may be dubious at best. Even though some people may have managed to pass their drug tests this way, they’re still not the best choice.

What’s Not Recommended

Tampering with your urine sample by adding adulterants like bleach, vinegar, goldenseal, and others, and using synthetic urine are not recommended methods as drug tests will easily detect any irregularities. 

Final Thoughts

THC is not easy to eliminate or to lower below cutoff levels, but it’s not an impossible process. Even though it stays in your body for a long period of time, there are ways you can help your body flush it out sooner, mostly by abstaining from marijuana use and drinking lots of water.

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.