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  • Writer's pictureMitchell Stern

How Long Does Weed Stay in Your System? - How to Pass a Drug Test

Updated: Feb 24, 2023

If you're searching for 'How long does weed stay in your system?' chances are that you've got a drug test coming up; and that you're ability to pass your drug test is questionable at best.

Don't worry, we've got you.

In this article, you're going to learn:

  • How long weed stays in your system

  • How drug tests are performed

  • Ways to induce a false negative result on your drug test

Table of Contents

How Long Does Weed Stay in Your System?

It depends. The commonly accepted answer is 30 days, but it could be up to 45 days for heavy users with slow metabolisms.

Conversely, a young person who only takes a couple of puffs of some dirt weed at a party may be able to give a clean test sample after only 14-15 days.

There are simply too many variables in the equation to be able to give a one-size-fits-all type of answer. These factors include:

  • Hydration habits

  • Metabolism

  • Age

  • Frequency of use

  • Amount of marijuana consumed

  • Quality of the marijuana

The reason weed stays in your system so long is that THC is fat-soluble and bonds easily with any lipid-based compound.

These compounds exist in abundance throughout the human anatomy and take time to break down.

Understanding Drug Tests

The first step toward knowing how to pass a drug test is understanding how drug tests are administered and performed.

On the day of your drug test, you'll likely be asked to give a urine sample. This sample will likely be collected in a purposefully-designed bathroom with little to no consideration for privacy.

You will likely be asked to empty your pockets and leave your belongings behind, although this is usually done on the honor system.

During sample collection, you may also be subject to observation.

If you're able to give your sample without anyone watching, consider yourself lucky.

How Are Drug Tests Performed?

After the sample is collected, the testing center will perform a variety of specimen validity checks. These are done to ensure the sample has not been compromised.

The extent to which specimen validity checks are performed varies from testing center to testing center.

Specimen validity checks include:


Temperature is the most commonly performed validity check. A fresh sample should be between 90.5 - 98.9 degrees Fahrenheit. Anything else will immediately send up red flags and cause the sample to be discarded.

Virtually every testing center monitors for temperature abnormalities.


The sample must have a pH between 4.0 - 10.0 to be considered valid

Specific Gravity

The sample should have a specific gravity between 1.005 - 1.030


The human body manufactures creatine at a constant rate. Low amounts of creatine indicate that the sample donor may be deliberately diluting their urine to mask a positive result.

A high amount of creatine would also be a red flag. A normal test sample should be between 20 - 400mg/dL of creatine.


Glutaraldehyde is a common adulterant that is used to mask positive results. Unfortunately, labs can also test for it and there's no excuse for having even trace amounts in your system.

Any sample must be negative for Glutaraldehyde.


Nitrites and other oxidizing agents can be used to induce a false negative result. However, like Glutaraldehyde, nitrites can be discovered by specimen validity checks.

Samples should be nitrite-free unless the donor is suffering from an infection like a UTI, in which case, the test result will be discarded.


After passing specimen validity checks, the sample will be screened using an immunoassay test. One of the most commonly used tests is the Enzyme Multiplied Immunoassay Technique (EMIT), although there are other types (RIA, FPIA, etc...)

If the results are positive, the test will then be confirmed with a GC/MS (gas chromatographer - mass spectrometer), which has the ability to identify any and all compounds within a given sample by breaking down the sample to the molecular level.

Once the sample is processed by GC/MS, the chances of a false positive are virtually zero, so it's essential that you pass the initial EMIT test.

The EMIT test relies on the concentration of THC metabolites, and therein lies its greatest vulnerability.


The standard USDOT cutoff is 50ng/ml of THC, although private industry may lower the cutoff to 25ng/ml in some cases.

Diluting your sample just enough, without using adulterants, is your best bet for passing a drug test.

If you're thinking about trying to excuse a positive result with the old 'Someone else was smoking it nearby' excuse, you should know that passive inhalation was only able to achieve 10ng/ml in test subjects.

Which Drugs Will a Urine Test Reveal?

There are three commonly-used drug screening panels. Although this article primarily focuses on THC, we will be discussing all three tests.

5-Panel Test

  • Amphetamines (meth, speed, ecstasy)

  • THC (marijuana)

  • Cocaine

  • Opioids (heroin, morphine)

  • Phencyclidine (PCP)

8-Panel Test

  • Barbiturates

  • Benzodiazepines

  • Propoxyphene

10-Panel Test

  • Methadone

  • Methaqualone

Does Delta-8 THC Show Up on a Drug Test?

Yes. Since the test is looking for THC metabolites and not just THC itself, Delta-8 will show up on a drug test.

Drug Testing Myths Debunked

Now that you know a little bit about what's going to happen on the day of your drug test, let's take a second to talk about what not to do.

Don't Rely on Excuses

If you think you're going to get off the hook with a clever excuse, think again. Drug testing centers have heard them all.

Here are the most common excuses:

I don't smoke weed, but someone was smoking near me.

In reality, passive inhalation only accounts for about 10ng of THC and cannot cause a positive result if standard cutoffs are used

I used to smoke, but then I stopped, and now when I exercise and burn fat, all the THC gets released into my blood

The truth is that body fat does not break down fast enough to release significant quantities of THC into the blood or urine

My romantic partner smokes and may have transferred some THC through sex

THC cannot be transferred through sexual contact

Here are some other things you should keep in mind:

Vinegar, cranberry juice, niacin & goldenseal won't help

  • These liquids supposedly shift the pH of urine and mask a positive drug test result

  • In reality, your body metabolizes the acid

  • Niacin does not increase your metabolism but may be used to disguise diluted samples

Strenuous exercise will not speed up the process

You simply can't burn enough fat in the time required.

Extended Cleansing is a Waste of Time

Cleansing before the day of the test won't actually purge your system of THC. Your body will continue metabolizing it at a constant rate until it's gone.

4 Strategies for Beating a Drug Test

Now that you know what not to do, let's take a look at what you should do to pass your drug test.

Most of the literature will tell you that the best way to pass a drug test is to abstain from drugs entirely. But chances are that the time for abstinence has passed, so let's delve into some real answers!


Deliberately diluting your urine sample is the best way to through off a metabolite test. Just follow these steps:

  • Fill your bladder with water 2-3 hours before the test

  • Pee 30 minutes prior to the test, and DO NOT give your first void urine of that day

  • DO NOT give first void urine during the test either. Make sure to pee a bit before collecting the sample.

  • Take B2 two hours prior to the test to color your urine yellow. Clear urine will through up red flags.


Diuretics will make you pee more and can help you dilute your urine on the day of the test. Common diuretics include:

  • Caffeine

  • Cranberry juice

  • Lasix (Furosemide) - Available by prescription only in the United States; but over the counter in Mexico


Although diluting your urine is helpful, it may not be 100% successful, especially in the case of heavy users.

One way to increase your odds of passing a drug test is to add an adulterant to the sample that will either mask the metabolites or oxidize (eliminate) them.


Tampering with a urine sample, in any way, is inherently risky. Aside from the obvious ethical issues, if you're discovered, your test result will be labeled a 'Fail.'

Cheating on a drug test is never forgiven, and you could even face legal consequences in some places.

Now, it's also true that not every lab takes the time to test for adulterants, but the technology does exist.

That being said, let's look at some common adulterants and examine how they work.


Visine is difficult to detect and will help mask a positive result. Just drop a few drops in the sample cup during collection.


Bleach will help "clean" a sample but can easily be detected by adulterant testing. You can surreptitiously introduce bleach into a urine sample by dripping a finger into a cup of bleach prior to the test and then subtly dipping your finger in the sample.

This will impart just enough bleach to clean the sample while hopefully staying under the radar in the event of an oxidizer check.

Just make sure to wash your hands after.


Use in the same way as bleach. Detergents are less effective but more difficult to detect and can be easily explained. Iodine is another good option

Clear Choice (Glutaraldehyde)

Although easily detectable and commonly tested for, glutaraldehyde deactivates most screening methodologies to produce a false negative result and cannot be reversed in a lab

Klear & Whizzies (Potassium and Sodium nitrite)

Nitrites are a powerful oxidizing agent that affects GC/MS confirmation of THC. However, nitrites are commonly tested for and are easy to detect.

However, your body will also naturally produce nitrites in response to a urinary tract infection. So, if you test positive for nitrites, your best bet is to claim that you're recovering from a UTI.

Urine Luck (Pyridium chlorochromate)(PCC)

Another strong oxidizing agent that affects screening methodologies and GCMS confirmation of THC and opiates. Although easily detectable and commonly tested for, the effects of PCC cannot be reversed in a lab.

Stealth (Peroxidase and peroxide)

This product combines two different compounds to form a powerful oxidizing agent that affects screening methodologies and GCMS confirmation of THC and opiates.

Unlike other adulterants, peroxidase and peroxide are more difficult to detect, though not impossible, and the effects cannot be reversed in a lab.


Another option is to substitute clean urine for your own. Although this presents several obvious challenges, including:

  • Obtaining clean urine

  • Getting the clean urine into the sample cup

  • Ensuring the urine passes the specimen validity checks, including temperature

If you find an answer to all of those questions, then more power to you; but this isn't a method we endorse.

Top 3 Detox Cleanses

Although their efficacy is questionable, some people still prefer prolonged cleanses. There are a number of products that claim to help you purge your system.

They include:

Natural Detox Ingredients

There are a variety of natural ingredients that may help you detoxify faster. The Yogi Tea brand has a trio of Detox teas that work well and taste great.

Some of the common ingredients in detox teas include:

  • Milk thistle

  • Cranberry

  • Dandelion root

  • Ginger root

  • Beet root

  • Yellow dock root

  • Parsley

Test Before You Test

Before you go in for your formal drug test, it's a good idea to buy a home-based drug testing kit and see whether or not you're likely to test positive.

Home drug testing kits are readily available and be purchased at your local pharmacy or on Amazon.

Legal Challenges

Although prospective employees have no legal right to challenge pre-employment drug screens, workers who are already employed may be able to mount a legal challenge in the event of a positive drug test.

Avoid signing anything that gives your employer the right to arbitrarily test you.

If you think you're being singled out for testing, consult an attorney to review your legal options.


You can object to having your urine tested on the basis of the 'right to privacy.' Mass testing violates the privacy rights of many in order to identify a small minority of drug users.

The Fourth Amendment to the Constitution protects individuals from unreasonable search and seizure and could potentially be used as a defense in the case of government jobs but may be less effective when used against private employers.


No test is infallible. Examinations of testing equipment have uncovered remarkably high error rates and poor quality control of samples.

In addition, urine testing only reveals past drug use and offers little to no indication of on-the-job performance.

In other words: Urine testing does not indicate toxication.


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