man covered in shaving cream

How Long Does Weed Stay in Your System?

Recent years have seen a massive shift in how Americans, the medical establishment, and state governments view the use of marijuana.

In spite of the federal government’s continued insistence upon keeping it illegal, nine states now allow legal recreational use. Twenty-nine additional states allow for medical marijuana use. And a handful more, while not outright legalizing it, have decriminalized marijuana.

How does all this progress translate into the workplace? If you’re lucky enough to be in a state with legal recreational use, does that mean no more drug testing?

Well, no. Not even close. All nine legal states have language in their laws that explicitly allow employers to drug test to detect marijuana, even if the employee does not show signs of impairment.

While cannabis advocates feel that smoking a joint is no different from having a glass of wine, most companies haven’t come around to that way of thinking yet. So, you want to know how long does weed stay in your system?

A significant number of employers still require at least a screening, and many also perform random testing on their current employees. And if you are in a job that has federal screening requirements, such as truck driving, there is no leeway here.

Types of Screenings Most Employers Require

laboratory technician holding and labeling sample tubes of urine

Let’s take a look at five main types of screenings:

  1. Urine test: This is pretty straightforward. You pee in a cup, and someone checks the urine for evidence of substance. 
  2. Blood test: A blood test is the most accurate form of screening, but it is also the most invasive and expensive of all the options. For this reason, it is rarely used for anything other than for medical or legal purposes.
  3. Saliva test: Saliva tests are quickly becoming a popular choice for drug test screenings because they are minimally invasive. A quick swab inside the mouth is all the tester needs to collect. However, it is also one of the least accurate screenings since it only reliably detects very recent use. Cannabis use has to have been within the last 4-10 hours for THC to show up in a saliva test.
  4. Perspiration test: This is one of the newer screenings on the market. The person submitting to the test wears a patch on the skin for two weeks. This patch collects the person’s sweat which then is tested for the presence of illegal substances. This form of screening is most often used in legal situations, such as child custody cases.
  5. Hair follicle test: Hair follicle testing is becoming more popular in some cases because it has proven to be better at detecting long-term, habitual use. It is more expensive than some methods, but hair test is a useful type of screening.

So how long does THC stay in your hair?

woman looking worried at her pink magenta color hair.

There is quite a bit of information out there regarding urinalysis screenings, but hair follicle testing is much less-known, so there are fewer resources available for those concerned about a positive test result and want to know how long does weed stay in your hair?

So how long does THC stay in your hair? Here’s what you need to know about this kind of testing and how long THC will stay in your hair follicles:

  • Hair follicle screening looks much farther into your past than other methods. This type of testing usually results in a positive test for those who have used cannabis regularly in the past 90 days. Some tests even claim to go back a full year. A urine test, on the other hand, typically only registers use within the past 30 days.
  • This test was developed to look for habitual users. An individual who uses marijuana on rare occasions is less likely to have a positive result with this screening compared to someone who indulges on a regular basis. For this reason, hair follicle screenings for THC or other substances are not suitable in situations such as car accidents when authorities are trying to find out what happened leading up to the event.
  • Hair follicle screening detects THC metabolites that attach to the root of the hair. Washing, dyeing, and styling will not affect the outcome of the test. It takes about 5-7 days after ingestion for the THC to reach the scalp.

How Does a Hair Screening Test Work?

A woman has pulled out a handful of hair and is sad.

If you are required to submit to a hair follicle test, you will likely need to do so within a few days of the request. These tests may be administered in a hospital or at the workplace using an in-home test that is sent in. 

On the day of the test, the examiner will first verify your identity. Afterwards, they will take a hair sample of 100 hairs from your head to submit. 

If you are bald or have very short hair, she may need to get a sample of body hair instead. The follicle is the muscle on the tip of the hair shaft that attaches it to the head. It looks like a small white bulb on the end of the hair.  Strands that naturally shed do not have a follicle attached. The hair strand or shaft is composed of the outside or cuticle, the middle or cortex, and the core or medulla.

The hair goes to a lab for screening, and if a positive result comes up, it will go through a second test to verify the results. Negative results are available within 24 hours; positive results require 72 hours because of the second screening.

Hair Follicle Test: Common Myths Busted

Hair follicle tests are sensitive, picking up THC amounts as low as one picogram per milligram, for those of you keeping track. Basically, it’s hard to sneak ANYTHING past this screening.

Can I shave?

Sure. Will it ensure a negative result on your screening? Probably not. Having no hair to submit will just mean that you have to go back when you do have hair. It’s also likely to raise the eyebrow of an interviewer who just saw you with a full head of hair. And a fresh haircut won’t help either since the examiner submits the 1.5 inches of hair closest to the scalp where THC concentrations are the highest, pun fully intended.

Can I shampoo it away?

Nope. The THC metabolites attach themselves to the hair follicle and are in the hair to stay. Shampoos, dyes, and styling products will not change that. Don’t waste your money.

Some people enjoy marijuana only on special occasions, some used back in college but have not in years, and quite a few use it habitually for medicinal or recreational purposes.

All are wondering how that will show on a hair analysis. The more you partake the easier it is to detect. This means if you are a one time, or infrequent user, it is unlikely that you will test positive in a hair analysis.

If you have not used since college, unless college was 90 days ago, you have nothing to worry about. This type of testing is meant to identify a regular user and if you think you fall into that category, you might be tempted to find a way to “beat” the test.

Bottom Line


Bearded man, wearing a green sweatshirt and sunglasses, smoking

Hair follicle testing is designed to weed out (again with the puns!) those who habitually use marijuana or other substances.

If you are an occasional partaker, you will probably pass just fine. If you are a regular user, and you know you will be job hunting in the coming months, you would be wise to take a break until it is out of your system and the new job is secured.

Are you worried about potential drug testing? While there isn’t anything we can do to prevent a positive result on hair testing, you might be interested in our products. 

You can purchase an at-home drug test kit to see how you would do or if you are lucky enough to get some kind of heads up, stop all marijuana use for 90 days before your test is best. 


About Chris Wilder

Chris Wilder spent many years working as a part-time phlebotomist, [and yes he knows all the vampire jokes] while honing his writing skills. In 2017 he gave up playing around with blood to become a full-time writer. While dealing with blood might seem a cold and analytical vocation, his role of phlebotomist required dealing with nervous patients who needed plenty of empathy and compassion, Chris has carried this over to his written work. He believes that Quick Fix Synthetic products are the best chance of success. With his wide knowledge in this field and his understanding of how urine drug tests can affect the lives of everyday people like you and me, Chris can explain in layman's turns all the important information you need to know. In his free time, he likes to hang out with friends and check out local bands drinking a glass or two of his favorite Makers Mark Bourbon, while enjoying a recreational smoke. To keep himself in shape he takes extremely short walks with Lola, his incredibly lazy pet pug.

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