If you are applying for a new job or dealing with a legal case, there’s a chance you might need to take a hair follicle test. This type of test involves examining your hair to see whether or not you have a history of drug usage, so it’s no surprise that it can feel stressful or invasive to some. Many people worry that hair follicle tests can detect drug use that happened months ago or identify drugs not found in urine tests. Do you really need to worry about a hair follicle test? Explore our guide to see just how far back they can detect drugs.
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What Is Hair Follicle Testing?
Hair follicle testing is a type of test that can identify drug or medication usage. It works by collecting a few strands of hair from your head and looking for the presence of certain drug metabolites inside of your hair. These substances are chemicals that your body generates while breaking down drugs. The metabolites end up in your bloodstream and eventually travel to your scalp. The protein structure of your hair can trap these metabolites and keep them long after they’ve left the rest of your body.
Substances Detected During Follicle Testing
Some follicle tests may only check for a specific drug in your system while others may examine your hair more thoroughly for any trace of any type of drug. Common substances found in hair follicle testing include:
- Heroin and other opioids
- Phencyclidine (PCP)
The Science Behind Hair Growth and Follicle Tests
To understand how long a hair follicle test lasts, it’s important to consider how hair growth and drug metabolites work. On average, people grow around half an inch of hair every month. This means that you grow around six inches of new hair each year. However, there is a lot of variation in hair growth rates. The food you eat, your age, and your personal metabolism can all affect how fast or slow your hair grows.
The drug metabolites that a test looks for are usually bound to the protein or the melanin in your hair. They only show up in the hair you grow around seven to 10 days after drug usage. Therefore, hair from a couple of years ago isn’t going to have drug metabolites from the drugs you took a month ago. Once metabolites end up in your hair, a lot of lifestyle changes affect how long these metabolites last. Hair treatments like bleaching or perming your hair can affect drug testing, and even the shampoos you use will affect how long drug metabolites last. The amount you sweat, how dark your hair is, and how oily your hair naturally is can all affect the amount of drug metabolites in your hair.
Disproving the 12-Month Myth
As you can see, a lot of different factors go into the detection window for a hair follicle test. Many people think these tests can detect substances up to 12 months in the past, but this is mostly a myth. This rumor tends to get spread because it’s a simple, round number that clearly shows the difference between hair and urine tests.
The reality is that hair follicle testing windows are a lot less precise. If two people take the same amount of a drug six months before a test, one person might test positive while the other tests negative. Everything from your diet to your personal hygiene habits will affect how accurate a hair follicle test is and how far back it can go. The amount of drugs you take and how often you take them also affects whether or not a detectable number of metabolites appear in your hair for months to come.
Realistic Detection Windows for Hair Follicle Tests
The length of time the test looks at will heavily depend on the length of hair collected for the test. In some cases, it might theoretically be possible to detect drug usage 12 months back or even further. However, most standard hair follicle tests only look at your recently grown hair. Especially if you have shorter hair, it’s impossible to see which drugs you were using a year ago. To help standardize testing, many labs only collect hair within 1.5 inches of the scalp. This means that they usually cannot detect drug usage more than 90 days in the past. The average hair follicle test is just for the past three months of your life.
|Can theoretically detect drug usage 12 months back or further, but standard tests typically focus on more recent periods.
|Hair Length Collected
|The length of hair collected heavily influences the detection period. Shorter hair limits historical detection.
|Many labs collect hair within 1.5 inches of the scalp to help standardize testing.
|Standard hair follicle tests usually cannot detect drug usage more than 90 days in the past, covering roughly the past three months.
Potential Limitations of Hair Follicle Testing
In addition to having very vague detection windows, hair follicle tests are also falling out of favor because they aren’t always accurate. 2017 research suggests that false negatives are fairly common. If a person’s hair hasn’t trapped a lot of drug metabolites, it can be harder for a hair follicle test to detect them. A 2015 study found that only about half of the people who reported recent cannabis use tested positive for the drug in a hair follicle test. Accuracy rates can range from around 2.9% to 65% depending on the drug.
Another challenge of hair follicle testing is that it works best on long, untreated hair. However, in most cases, it can be very hard to dictate how people care for their hair. By the time a hair follicle test is ordered, a person may have cut their hair or treated it in a way that makes it harder to detect drug metabolites.
Ultimately, hair follicle tests can be a useful tool, but they’re not entirely foolproof. Until you take the test, it can be quite hard to tell whether or not a hair follicle test will detect past drug usage. If you’re tired of having to worry about how far back a hair follicle test can detect drugs, getting clean is one of the most effective solutions. Sober living makes it easy to face drug tests with confidence.
At Live Free Recovery Services, we’re dedicated to helping our clients succeed. We offer compassionate, evidence-based care that gives you the tools you need to overcome addiction. To learn more about our services, contact our team today.
Can a hair follicle test go back 12 months?
A hair follicle drug test can detect drug use going back approximately 12 months, it depends on the length of the hair sample collected. Typically, a test can detect drug use for up to. However, a hair sample taken from a part of the body where hair grows more slowly, like the legs arms, may have a detection window of up to 12 months. Overall, the typical detection window head hair follicle drug test is 90 days, but a longer history of up to 12 months is possible with hair from slower growing areas.
Published on: 2024-02-12
Updated on: 2024-02-12