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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

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?

Understanding Drug Tests

Which Drugs Will a Urine Test Reveal?

Drug Testing Myths Debunked

4 Strategies for Beating a Drug Test

Top 3 Detox Cleanses

Natural Detox Ingredients

Test Before You Test

Legal Challenges

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