Last updated : July 14, 2025
If you have long hair and in your 40’s, will a hair test show what you did in college? Hair grows at a rate of approximately ½ inch per month. So, in theory, if you had hair that was 18 inches long, and you tested the ends of the strands, then you could find drugs consumed more than 3 years ago!
Don’t panic, laboratories today test the end of the hair cut from the root about 1.5 inches which provides a 90-day drug use history. Many employers use hair testing for their pre-employment or random programs to help ensure that applicants and employees are drug-free. Employers may decide to use hair testing because of its long window of detection, simple collection process and tendency to be difficult to cheat or adulterate.
The collector obtains a 100 milligram sample of hair (90 to 120 strands) cut at the scalp. The collector secures the hair sample in foil and completes chain-of-custody documentation in preparation for shipment to the testing laboratory. Since hair samples are obtained in full view of the collector, the process minimizes the likelihood of sample adulteration or specimen substitution. Hair can be collected from several head locations and combined to obtain the required amount of hair. In addition, body hair may be used as a substitute to head hair; but collectors do not combine head hair and body hair. Most of the issues with hair testing stem from the collector not providing adequate quantity of hair to the laboratory.
Is hair testing more expensive then urine drug testing? Yes it is, but you also get more information about the person being tested. Do you really want to hire a drug user? You should do everything possible when hiring a new employee to make sure they are not a drug user and not a thief. Do you really want to know? With a urine test most people can stop using drugs for a week out and pass a drug test. This is not possible with a hair test.
In November 2013, companion bills that would require the Department of Health and Human Services to recognize hair testing as an option for carrier compliance of drug testing requirements for truck drivers were introduced this week in the House and the Senate. The bills are aimed at preventing lifestyle drug users from landing jobs as commercial truck drivers. Before the U.S. DOT can authorize hair testing for illegal drugs in place of urine testing, the U.S. Department of Health and Human Service would likely have to authorize such standards first. Trucking companies currently drug testing truck drivers for hair in a non-DOT environment include: J.B. Hunt, Schneider National, C.R. England and Gordon Trucking. Safety officials at these companies guessed that when they started testing hair, they were going to catch quite a few people who had slipped past urine tests. They were right.
Why Hair Testing:
One of the major advantages of using a hair test is because of the longer window of detection, drug abusers should be detected at a much higher rate than urinalysis. It is without a doubt very difficult to cheat on a hair drug test. In side-by-side comparison studies with urinalysis, hair drug testing has uncovered significantly more drug use. In two independent studies hair drug testing uncovered 4 to 8 times as many drug users as urinalysis. The cost of a hair test is far less than the cost an employer will experience when hiring a substance abuser.
