Fraser Horton
Fraser Horton
Last Updated on June 11, 2021

Hair drug testing has been a practice since the 1970s when employers first started testing their employees for illicit drug use. Today, common drug tests include blood, urine, saliva, and hair tests that test for the presence of common drugs and opiates. Tests most commonly screen for the presence of the following drugs:

  • Barbiturates;
  • Benzodiazepines;
  • Amphetamines;
  • Methamphetamines;
  • Opiates;
  • Opioids;
  • Codeine;
  • phencyclidine (PCP);
  • Methadone;
  • Oxycodone;
  • Cannabis.

The test checks for the presence of drug metabolites and drug residues by looking at the federally appointed cutoff level which determines whether you get a negative or a positive drug test result. 

If you’ve been researching hair follicle tests for cannabis use and you’re wondering how long cannabis is detectable in hair samples, as well as how you can pass the test, read on.

How Does Weed Get in the Hair?

After weed consumption, cannabinoids go through the bloodstream, and cannabinoid metabolites end up scattered throughout the body. Once you’ve smoked or ingested cannabis, its metabolites always end up in the bloodstream and get in your hair via the bloodstream.

Cannabis metabolites bind to the tissues and cells around the root of your hair (underneath the surface of the scalp), and they can stay there for about three months. As the hair grows, the cannabinoids become incorporated into the hair follicle, therefore they’re incorporated in the hair strand. It takes about 10-15 days for this to happen, after which you could get a positive result on your hair follicle drug test. It takes one picogram of THC per milligram to trigger a positive test result.

Technicians cut and test about 100 strands of hair. Since human hair grows at a rate of 0.5 inches per month, testing the 1.5 inches of hair (the length that would grow in 3 months) near the root will show if you’ve consumed cannabis or not. That’s why testers check the bottom part of the hair.

What Is the Hair Follicle Drug Test?

While urine tests look for recent drug use, hair follicle drug tests show habitual and regular drug use. Since they have the longest detection window of all tests (it has a 90-day window), they’re nearly impossible to pass if you’re a regular weed user, and as a result of that, they’re commonly used as evidence in the court of law. 

The procedure requires the tester to take 1.5 inches of hair and test it to figure out your weed habits. After consuming weed, it takes about 5-10 days for the cannabinoid THC to bind to the hair and show on a hair drug test. If you’ve smoked weed in the past three months, you’re likely to fail the test as human hair doesn’t grow that fast.

The long detection window often makes some cannabis users uneasy, especially if their work requires mandatory drug testing. Therefore, people try to find ways to pass the test by:

  • Shaving their hair off;
  • Using detox shampoos;
  • Using home remedies (detox salts, vinegar, tar shampoo, and others).

Please note that the above examples are purely for informational purposes only. We’re not recommending that you cheat your way out of drug tests especially if it’s illegal in your state/country.

Below we’ll discuss the above methods in detail for educational purposes.

How to Pass a Hair Follicle Test?

There are a few things that you can try if you have a hair drug test pending. 

Stop Consuming Cannabis

No detox method can help you if you don’t quit cannabis before your drug test. As with the saliva, blood, and urine drug test, you need to give your body time to start eliminating THC metabolites. Hair analysis for cannabinoids is pretty exact, so make sure you give your body enough time to get back on track.

Aloe Rid Detox Shampoo and Zydot Ultra Clean Shampoo

Doing a shampoo detox may clean your hair and remove drug toxins from the hair shaft so you’re left with no traces of drug use. These shampoos are often used a day before the test, and often with a purifier (to provide a chemical coating on your hair) and a conditioner (so the hair doesn’t look like it’s been tampered with). Products that are often used for such purposes include Old Style Aloe Rid Shampoo and Zydot Ultra Clean Shampoo, often together with the Macujo Method.

The Macujo Method

This is one of the most popular methods in online communities that can help pass the hair follicle test. However, there’s no evidence that it’s 100% effective. People often use it when they’ve used cannabis recently and need to pass the hair follicle test.

  1. Stop using cannabis before your test.
  2. Damp the hair with warm water, apply vinegar, and massage the roots for at least 10 minutes (note that if you have a sensitive scalp, vinegar may cause irritation).
  3. The goal is to remove the oil from the roots of the hair, so don’t soak it or you’ll be adding an additional barrier on top of the hair oil.
  4. Add a few pumps of Neutrogena Clean and Clear and massage the mixture into the scalp and hair (the aim here is to break open the hair cuticles so you can rinse out the metabolites).
  5. Keep the mixture for half an hour under a shower cap, and then rinse thoroughly.
  6. Use Old Style Aloe Rid Shampoo or Zydot Ultra Clean Shampoo, and rinse again.
  7. Use the shampoo once more and rinse.
  8. Wash again with a few drops of laundry detergent (keep in mind that your hair and scalp might get damaged).
  9. Do the method three times the day before your test.

The Jerry G Method

A 1997 study showed that bleaching and dyeing your hair greatly reduces the detection of drug metabolites, hence the Jerry G Method which was developed as a way to beat a hair drug test. This method starts 10 days prior to the drug test. 

  1. Stop using cannabis before your test.
  2. Bleach your hair and use a permanent hair dye same as your natural color after you’ve bleached it. Do this 10 days before the test.
  3. After you’ve bleached and dyed your hair, wash it with Old Style Aloe Toxin Rid Shampoo.
  4. After 10 days, bleach and dye your hair again, and wash it with Old Style Aloe Toxin Rid Shampoo.
  5. On the day of your test, make a paste out of baking soda and water, and apply it to your hair. Keep the mixture on your hair for 2.5 – 3 hours and rinse with water afterward.
  6. Wash again with Toxin Rid, and rinse with water.
  7. Wash again with Zydot Ultra Clean Shampoo.

Bleaching and dying the hair may damage the strands enough so testers won’t be able to detect THC metabolites.

Final Thoughts and What Not to Do

Hair follicle testing is hard to trick, so the best option would be to go the natural detoxification way which takes about 90 days and will enable you to have the desired results on your mandatory drug screening. 

The worst thing to do would be to shave all your hair, since that will result in the testers taking body hair (like armpit hair), which will make it harder for you to pass the test since body hair grows at a much slower rate and replaces itself less often compared to head hair. Keep in mind that a lot of people get caught while trying to beat the hair follicle test, and losing your job for that reason isn’t good for your CV. Or worse, you can face criminal charges and end up in prison if it’s illegal in your country/state. Therefore, your best bet would be to wait it out and detox naturally for at least 90 days.


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.