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Hair Follicle Drug Testing Facts

Some employers test job applicants for drug use as part of routine pre-employment procedures. The tests are usually conducted as a condition of job offers, so applicants must “pass” before starting work. Although testing often is conducted through a urine or blood sample, it also can be done through hair follicles. Some employers prefer hair tests because they detect drug use within a longer time period, and are considered more accurate and less invasive then other tests.

In addition to pre-employment screening, some employers may choose to conduct drug tests of employees after an accident or if they have reasonable suspicion that an employee has been using drugs. However, because it usually takes 5 to 10 days for drugs to appear in hair follicles, employers typically use other drug testing procedures in that situation.

Test Procedure

Tests typically are performed by collecting a hair sample and sending it a laboratory for testing. If a person is bald, a sample may be taken from his body, although pubic hair is not used. Hair collected from a brush also cannot be used. Usually only 1 1/2 inches of the hair, as measured from the root end, is tested. Since hair grows approximately half an inch per month, a hair follicle test can detect drug use within a 90-day time frame.

Drugs commonly tested for include:

  • Cocaine
  • Marijuana
  • Opiates, such as codeine and morphine, 
  • Amphetamines like methamphetamine, MDMA, and MDA
  • Phencyclidine, commonly known as PCP. 

Other drugs that may be tested for include hallucinogens, inhalants, anabolic steroids, and hydrocodone -- prescription medication known as Lortab, Vicodin, or Oxycodone. Hair drug testing does not detect alcohol use, according to Laboratory Corporation of America, which conducts these tests.

According to the Department of Labor, “The accuracy of drug tests done by certified laboratories is very high, but this certification applies only to the five substances tested for in federal drug-testing programs (amphetamines, marijuana, cocaine, opiates, and phencyclidine) and alcohol."

Drug Testing Laws

No federal law prohibits employers from test job applicants for drug use, although many state and local government regulate those tests. Some common rules that employers must follow are notifying applicants through job postings or application forms that drug testing is part of the screening process, ensuring that all applicants are tested in the same fashion, and having tests conducted at a state-certified laboratory.

Challenging Drug Tests

Employees can refuse to submit to a drug test, although if they are fired because of it, they may have no legal recourse. In some states, workers in these circumstances may be denied unemployment benefits. Workers who have been given drug tests and suspended or demoted as a result may be able to fight it if they can prove the drug tests were not conducted under the procedures outlined by the laws in their states.


Natalie Keith is currently a marketing copy editor for Boca Raton, Fla.-based book publisher Taylor & Francis Group. She has also been a journalist in Florida since 2004, specializing in real estate and construction. Among past assignments are writing and editing for publications such as Real Estate Weekly, New York Construction, Inman News, and Scaffold Industry magazine.