How Long Does THC Stay in Your Hair?

thc in hair follicles
By Rebecca Olmos Updated March 8th

Fact-checked by Deb Tharp

Hair follicle drug tests are one of the most common types of drug tests. This leads many cannabis users to wonder: “How long does THC stay in hair follicles?”

When consumed, THC enters the bloodstream and reaches several different body parts, including the hair follicles. As the hair grows, the THC remains in it. While the cannabinoid remains in the hair longer than other bodily excretions, like urine or skin cells, the results of the hair follicle tests may not always be reliable. 

This article will clarify how long THC stays in the hair, the process of testing hair follicles, and how to detox your hair to prepare for cannabis drug testing.

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THC and Your Hair

THC is short for delta-9-tetrahydrocannabinol. It is the main compound in the cannabis plant, responsible for many of the reported therapeutic and psychoactive effects, known as the “high.” 

THC naturally exists in the plant as THCA, the non-active form of THC, and converts to THC when heat is added in a process known as decarboxylation. Once consumed, the THC enters the body and is dispersed through the bloodstream. From there, it interacts with various parts of the body and brain through the endocannabinoid system.¹ 

One of the places THC can be transferred into is the hair, via the sebum–an oily substance naturally produced by the body. It is excreted through the skin and the hair, which helps to lubricate the hair follicle. 

THC can also end up on the hair via contamination or application, like through the fingers after touching cannabis material², touching contaminated surfaces, or applying a cannabis topical directly to the hair or skin. Through this mode of transfer, others who may not have consumed cannabis directly may have traces of THC found on them. This is one of the reasons researchers believe hair follicle drug tests may produce inaccurate results.³ 

How Long Does THC Stay in Hair Follicles?

hair drug test

When consumed, THC from the cannabis product enters the body and interacts with the endocannabinoid system to deliver its effects. THC and other cannabinoids remain in the body, absorbed and stored in fat until excreted through bodily fluids.⁴ 

Through some testing methods, clinicians can detect cannabis in the system as long as 2 to 5 days for light users and 1 to 15 days after the last exposure for heavy users. So, even if you have abstained from cannabis use for a few days before your drug test, THC may still be detectable. Urine samples, especially in heavy consumers with high body fat, can detect THC consumption up to 30 days after the most recent use.

Hair samples can detect usage as far back as 90 days.⁵ The extended time that cannabis stays in the hair makes hair follicle testing ideal for those looking to detect usage further back in time, in cases where pre-employment screening is needed. 

Several factors can affect how long THC stays in hair follicles, and as the hair grows, the traces of THC remain in the hair and follicle. These factors, along with the frequency of use, dosage, metabolism, method of use, and other health factors, like diet and exercise, all affect the length of time THC stays in the system.⁶ 

What is a Hair Follicle Drug Test?

Hair Follicle Drug Test

When THC enters the body, it is metabolized into a byproduct called THC-COOH, the substance detected in drug tests to give a positive result. The body can store this byproduct in places like fat cells for weeks or months. 

In hair follicles, clinicians can detect cannabis up to 90 days past usage, but in some cases, depending on the hair growth rate, THC can be detected for up to 12 months.

To conduct a hair follicle test, clinicians will collect 100 to 120 strands of hair from either the head or other places on the body. The hair is then sent to the lab for testing. 

While the hair may hold on to THC the longest, there is some noted unreliability with these tests, with one report finding that cannabis was only found in 52% of the hair samples of self-reported cannabis users.⁷  

Hair follicle tests have also been linked to racial bias. One review found that some drug compounds link to melanin, a compound found in darker hair. In comparison to less pigmented hair, higher concentrations of drugs were found in darker hair, despite equal administration of drug dosage.⁸ 

Although hair follicle tests can better detect cannabis use in high-use consumers, THC can also be detected in one-time drug use. The potential to produce a false positive and long turnaround time makes the test unsuitable for all employers. Hair follicle testing is not federal testing approved. 

How to Pass a Hair Drug Test

Pass a Hair Drug Test

The only way to guarantee you pass a drug test without fail is by abstaining from cannabis use. For users who are unable to abstain from cannabis use, like medical patients, this may not always be a realistic option. In these cases, it may be better to search for an employer who does not require drug testing.

For those who can, a detox is the next best method when trying to pass a hair follicle drug test. Detoxes should start 60 to 90 days before your test if possible. Natural detox methods are the safest and include lifestyle changes, like diet and exercise. 

Be mindful, though, while exercise may increase the rate at which cannabis is detoxed out of your system, it may also increase the likelihood of a positive test in the short term. This is one reason why it’s best to start detoxing from cannabis as soon as possible.

Some cannabis users turn to hair removal methods, like shaving, in order to remove hair before a follicle test. While this can eliminate some areas that the test administrators may take a sample from, it can also lead them to believe that you are dodging the test. Additionally, hair samples may be taken from several parts of the body.

Some users have turned to resources that claim certain shampoo products will remove traces of THC or cannabis from the hair. Not only do these products contain ingredients that may damage the hair and scalp, but they also may be traceable through drug tests. And depending on the state you are in, trying to cheat a drug test may result in serious legal penalties. 

The best way to ensure that all traces of cannabis are out of your system is to abstain from consumption for as long as possible. If you are a daily or high dose consumer, be mindful of adverse potential withdrawal effects, including irritability, headaches, reduced appetite, or increased anxiety. 

If you are a medical cannabis patient, consult your doctor before changing your dosage or preparing for a drug test.

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What About CBD and Hair?

CBD is short for cannabidiol, another cannabinoid found in the cannabis plant that has become increasingly popular over the years. It provides several different therapeutic benefits without the intoxicating effects of THC. It has been used by patients to treat pain, inflammation, and epilepsy.

Since CBD does not produce an intoxicating effect, users wonder if CBD stays in the system and will affect a drug test like the hair follicle test. Since many drug tests are testing for traces of THC-COOH, CBD is unlikely to trigger a positive result.

Users should still be mindful of the type of CBD they consume. CBD products are unlikely to cause a positive drug test result only if the CBD products they consume are an isolate with zero traces of THC. While hemp-derived products may say that they are CBD only, they may still contain up to 0.3% THC. These small traces may not be detectable if the user consumes small sporadic dosages, but this may be different for daily consumers.

CBD products purchased in a dispensary are more often than not going to contain small traces of THC. Make sure to read the label fully if you are worried about the presence of THC in your system.

If you are consuming products with trace amounts of THC in them, the cannabis will stay in your system similarly to THC-rich products: stored in fat cells and passed through the body via urine, sebum, hair follicles, or other secretions. In these cases, it’s best to follow the same natural detox methods as you would for high-THC products. These methods include abstaining from CBD consumption, as well as changing your diet, and exercising. 

Various factors will affect how long CBD stays in your system, including dosage, metabolism, diet, type of product used, and frequency of use. 


Sebum excretions of the skin are just one way THC can leave the body, making hair collection and testing one of the most common ways to test for cannabis use. THC can remain traceable in the hair for up to 90 days and sometimes longer. CBD is unlikely to trigger positive drug test results, but users should still be mindful of the type of products they are using to make sure no amount of THC is present. 

While it may be tempting to shave your entire body of hair before taking a hair follicle test, that may be more suspicious than practical. And even if you are able to come back and retake the test when your hair grows back, the shaving will not have removed any remaining traces of THC in your system.

Several factors will affect how long cannabis remains in your hair, including your dosage, method of consumption, frequency of use, diet, metabolism, and even the length and color of your hair. The most effective way to remove any traces of THC in your system is to naturally detox the body through abstinence of use, diet, and exercise. 

It can be tempting to turn to quick-fix, over-the-counter products that claim rapid results, like shampoos, but the chemicals in these products may do more harm than good. They could potentially harm your hair or scalp and be detectable on the drug test. Depending on where you’re living, tampering with your drug test may result in serious legal consequences. 

Detox methods may also induce withdrawal effects in some users. Consult with a physician if you are a medical cannabis patient or are worried about adverse effects from changing your consumption habits. 


¹ Lu, Hui-Chen, and Ken Mackie. “An Introduction to the Endogenous Cannabinoid System.” Biological Psychiatry, vol. 79, no. 7, Apr. 2016, pp. 516–525,,

² Paul, R., et al. “Detection of Cannabinoids in Hair after Cosmetic Application of Hemp Oil.” Scientific Reports, vol. 9, no. 1, 22 Feb. 2019, Accessed 12 Feb. 2020.

³ Moosmann, Bjoern, et al. “Finding Cannabinoids in Hair Does Not Prove Cannabis Consumption.” Scientific Reports, vol. 5, no. 1, 7 Oct. 2015, Accessed 26 Mar. 2020.

⁴ Sharma, Priyamvada, et al. “Chemistry, Metabolism, and Toxicology of Cannabis: Clinical Implications.” Iranian Journal of Psychiatry, vol. 7, no. 4, 2012, pp. 149–56,

⁵ Hadland, Scott E., and Sharon Levy. “Objective Testing.” Child and Adolescent Psychiatric Clinics of North America, vol. 25, no. 3, July 2016, pp. 549–565,,

⁶ Wong, Alexander, et al. “Exercise Increases Plasma THC Concentrations in Regular Cannabis Users.” Drug and Alcohol Dependence, vol. 133, no. 2, 1 Dec. 2013, pp. 763–767,,

⁷ Gryczynski, Jan, et al. “Hair Drug Testing Results and Self-Reported Drug Use among Primary Care Patients with Moderate-Risk Illicit Drug Use.” Drug and Alcohol Dependence, vol. 141, Aug. 2014, pp. 44–50,

⁸ Bourland, James. Hair Color Bias Literature Review.

The information in this article and any included images or charts are for educational purposes only. This information is neither a substitute for, nor does it replace, professional legal advice or medical advice, diagnosis, or treatment. If you have any concerns or questions about laws, regulations, or your health, you should always consult with an attorney, physician or other licensed professional.

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