Medically Reviewed by
Jason Crawford

Article Last Updated on January 14, 2023

Drug testing in the workplace is much more common nowadays than it used to be and it’s also becoming a frequent prerequisite for job applications.

For non-users, a drug test wouldn’t be a big deal, but for cannabis users, it can be disconcerting, and understandably so because it can cost them their source of income. Marijuana is still federally illegal, despite the legalization in most states, so many employers treat it as such.

By far, urine drug tests are the most commonly used because they’re inexpensive and pretty accurate. However, hair testing, although not as commonly used, is gaining favor over other types of drug testing because it’s the most accurate, and its detection window is much longer compared to other tests. Additionally, it’s the hardest to pass.

However, many people claim that there are ways you can get THC out of your hair, or at least render it undetectable by the test if you have an upcoming appointment.

In this article, we’ll explain how the hair strand test works and what methods are commonly used in the weed community to lower the traces of THC (tetrahydrocannabinol) in the hair. But of course, we are not recommending cheating your way out of a drug test – so the content of this article is purely for educational purposes only.

How Does THC Get In the Hair Shaft?

When you consume weed, the cannabinoids (THC and CBD) first get into your bloodstream, and then they get carried to the liver where they get broken down into byproducts. From there, the byproducts, also called metabolites, get stored in the body fat because they are fat-soluble.

THC metabolites mainly get deposited into the hair shaft through the sebaceous glands on the scalp that secrete a natural oil called sebum to protect the scalp from overdrying. Only a small portion of the THC metabolites get to the hair shaft from the bloodstream. 

As your hair grows from the hair follicle, the THC metabolites become incorporated into the structure of the hair strands. It usually takes 5 to 10 days for the metabolites to reach the scalp surface and be incorporated into new growing hair strands.

This is why hair follicle drug tests are so accurate – THC literally becomes a part of your hair. This, however, doesn’t happen only with THC but also with any other drug or medication. So, as you can see, your hair strands contain the history of your cannabis consumption, which is the reason why these tests are used to detect habitual drug use. 

Most tests look at the past 90 days of drug use, but some employers may order tests that go further back in time, like 6 or 9 months. However, due to environmental changes and chemicals in the hair, the test loses its accuracy beyond the 90-day mark.

How Does Hair Follicle Drug Testing Work?

The hair follicle drug test is designed to detect one particular THC metabolite called THC-COOH at a minute concentration of 50 ng/ml (nanograms per milliliter). Since the cutoff level is very low, the test is very sensitive, and therefore accurate.

Testing labs will need a small sample of hair that will be cut off from the top or the back of your head close to the scalp. The hair sample will be 1.5 inches in length because human hair grows about 0.5 inches every month, so 1.5 inches of hair would cover a period of 90 days.

If you shave your head or are naturally bald, you will be asked to provide a sample of body hair.

Hair Testing In Comparison to Other Types of Drug Tests

The biggest difference between the different types of drug tests is the detection time. The hair follicle drug test has the longest detection window among all types of drug tests and it’s used to detect habitual drug use. The urine test may be the most commonly used, but it only detects recent drug use, from 3 days up to 30 days. Saliva tests can detect THC within 72 hours, while blood tests have the shortest detection window of just 4 hours.

Commonly Used Methods for Getting THC Metabolites Out of the Hair

The most obvious solution would be to abstain from consuming weed long enough, or until your new hair growth is free from THC metabolites. 

However, the time frame for a natural THC detoxification is at least 110 days for occasional to regular users, and over 150 days for heavy users, and in most cases, drug tests are announced only a few weeks in advance. Ceasing your cannabis use immediately is always recommended, but people often look for alternative solutions, like detox products.

Bottom Line – Detoxing for an Extended Period of Time Is the Safest Way to Get THC Out of Your Hair

Being surprised with a hair follicle drug test at work isn’t music to anyone’s ears, so naturally, you would want to avoid getting positive test results. However, it’s not always so simple. The way THC metabolites deposit in your hair makes it nearly impossible to cheat, and not to mention the legal repercussions you might face (which is why we don’t recommend it).

Therefore, if you can afford to do a natural detoxing, do so. That way, you wouldn’t have to risk facing the law or damaging your hair and scalp with harsh chemicals by going through so much trouble that doesn’t guarantee any success.

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.