US Drug Test Centers Blog
1 in 5 Hair Drug Tests Come Back Positive. Here Is What a Hair Test Shows.
In July 2026, the Quest Diagnostics Drug Testing Index reported something that caught many employers off guard. Nearly 1 in 5 workers who took a hair drug test in 2025 tested positive. That is 19.1%, up from 13.1% in 2021.
Compare that to urine tests, where the positive rate was 4.3%. Same workforce. Very different picture. So what’s going on, and what does a hair test actually tell you?
How a Hair Test Works
When you use a drug, it travels through your blood. Your blood feeds your hair follicles, and tiny amounts of the drug get locked into the hair as it grows.
At the collection site, the collector cuts a small sample of hair from close to the scalp, about the width of a pencil. It does not leave a bald spot. If head hair is too short, body hair can sometimes be used. The lab then tests that hair for drugs.
How Far Back Does a Hair Test Go?
A standard hair test looks back about 90 days. Head hair grows about half an inch per month, and labs usually test the 1.5 inches closest to the scalp.
One thing people do not expect: a hair test is not good at catching very recent use. It takes about a week or more for hair containing the drug to grow above the scalp where it can be cut. So a hair test is about patterns, not last weekend.
Why the Positive Rate Is So Much Higher
There are three big reasons hair tests catch more:
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A longer window. A urine test sees a few days. A hair test sees about three months. Someone who uses every other weekend may pass a urine test with good timing, but not a hair test.
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Harder to cheat. The collector watches the sample being cut. There is no cup to swap and nothing to dilute.
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It shows ongoing use. Quest noted that hair results may reflect recurring or chronic use, not one-time use.
What Hair Tests Are Finding
In 2025, Quest found that hair tests were positive for:
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Marijuana: 15.1%, up almost 59% from five years earlier
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Cocaine: 4.0%, up from 2.7% in 2021
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Methamphetamine: 2.5%, up from 2.1% in 2021
Marijuana made up more than half of all positive hair tests.
What a Hair Test Doesn’t Do
A hair test is a strong tool, but it’s not the right tool for every job.
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It does not show impairment. It cannot tell you if someone is high today.
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It is not ideal after an accident. For post-accident or reasonable suspicion testing, you want a test that catches recent use, like a mouth swab or urine test.
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It is not accepted for DOT testing. DOT-regulated drug tests must use urine for now. Hair testing can be part of a non-DOT program, or used separately where state law allows.
Myths about passing a hair test
You will find plenty of shampoos and "detox" methods online. Here is the reality:
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Special shampoos may remove a little from the outside of the hair, but the drug is locked inside the hair shaft.
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Bleach and dye can lower drug levels somewhat, but labs can still detect use, and heavily treated hair is a red flag.
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Shaving your head means the collector will take body hair, which can have an even longer window.
When should employers use hair testing?
Hair testing works best when you want to know about a pattern of use. Common uses include:
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Pre-employment testing, to see the last three months, not just the last few days
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Random testing in non-DOT programs
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Programs with past cheating problems, because the collection is hard to tamper with
Many employers use more than one test type. For example, hair for pre-employment, urine for DOT-required tests, and mouth swab for post-accident testing.
How US Drug Test Centers can help
US Drug Test Centers offers hair testing for employers and for individuals, including EtG hair testing for alcohol. We can help you decide where hair testing fits in your program and set it up at collection sites nationwide.
Call 866-566-0261 or visit www.usdrugtestcenters.com.
