How Far Back Does A Hair Follicle Test Detect Drugs?

How Far Back Does A Hair Follicle Test Detect Drugs?


Hair Follicle Drug Tests can trace the usage of certain illegal drugs for an extended amount of time, say, a maximum of 90 days. The main reason behind the introduction of the hair follicle drug test is their accuracy and their longer detection period which other drug testing methods will find it difficult to trace over. That is the reason they are preferred over other drug testing methods despite their complex testing process.

hair follicle test

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We use chemicals and other forms of drugs every day in and day out, but what makes it illegal is the amount of intake. There are two ways where a person gets addicted to illegal drugs, either intentionally or unintentionally.

Considering the unintentional factors, the drugs that we consider illegal are used in different drug forms or combinations. Doctors are very much aware of these and hence prescribe a moderate amount so that the patient does not consume excessively leading to overdose and addiction. However, some patients do take more than the prescribed dose which leads to an overdose of the medication, subsequently leading to addiction.

Pertaining to the intentional factors, it is obvious that some people use these drugs either via false prescription or through smuggling to get addicted. In contrast, the drug testers have come up with various drug testing methods to prove them guilty. However, they were not effective and were open to loopholes. This is where the Hair Follicle Drug Test came to the rescue.

What is a Hair Follicle Drug Test?

Hair follicle drug testing is one of the drug testing methods where a hair sample is collected from the head or any other parts of the body to test for the presence of prime illicit drugs. The hair sample tests became prominent because of their accuracy and their extended detection period. It was in 1987, where NIDA considered “Hair” as a specimen for testing for drugs. Due to their accuracy, it had been approved by the FDA to consider Hair Drug Testing as one of the testing methods for detection of drugs.

Be it pre-employment, random, post accident, followup or during probation, hair drug tests outperformed other drug tests by their accuracy percentage in various fields. The below table demonstrates the efficiency of the hair follicle drug test compared to the urine and oral fluid tests.

The lab test results in 2003-2007 differed drastically when the hair drug tests were considered. The urine tests and oral fluid tests carried 4.15% and 4.73% positive test result rates whereas the hair drug tests carried a successful positive detection rate that stands at 10.73%.

The Massachusetts Civil Service Commission identified hair drug test as a progressive drug testing method in March 2013. Considering the facts, screening the hair sample for drugs is taken upfront for major drug crime identification tests and in major institutional testing.

Subsequently, the SAMSHA identified the usage of Oral and Urine drug testing for short-term drug exposures, and Hair and Nail drug testing for long-term exposures.

Hair drug tests cannot detect all the drugs that are considered illegal, but they can detect the presence of major illicit drugs that are preferred by most of the institutions during pre-employment, probation or other causes.

Major Drugs That Hair Drug Test Can Detect

Hair drug tests can easily identify the below-mentioned drugs for up to 90 days after last consumption.

  1. AMP
  2. COC
  3. MAMP
  4. MDMA
  5. PCP
  6. THC
  7. Alcohol
  8. Opioids

The hair drug tests performed well in identifying the above-mentioned drugs in an effective way and the positive test rates during the period 2003-2007 for non-regulated workplace workers were precise.

The below mentioned comparative chart pictures the efficiency of the hair drug tests for all the major illicit drugs in the United States.

The accuracy for COC usage in the non-regulated workplaces was higher during the period 2003-2007. This was rightly identified by the hair follicle drug tests with accuracy when compared to urine and oral fluid samples.

You may be wondering “How long the hair follicle drug test can detect drugs?” The maximum limit of the detection period is 90 days, but it differs based on the drug variety and the amount of intake.

It should be noted that not all the drugs retain in the hair for such a long time (90 days). For instance, alcohol stays in the hair for a maximum of two days, after which it is difficult to trace the drug metabolites. There are high chances of tracking if the individual is a regular drug abuser. For an occasional drinker, the drug traces may be visible in a feeble amount in the preliminary test which could be confirmed on the confirmatory testing.

How Does The Drug Traces Enter Into Hair?

This is a reasonable question since the hair is considered to be a dead cell. To be clear, keratin is a connective tissue that connects the hair to the root. As the hair grows, the nutrients and other molecules that circulate in the blood enter the hair via keratin. They get stored in the hair for a long time as they are locked up as a dead cell and have no exit point.

This helps the laboratory testers to trace the drug usage by the individual. The concern is that drug metabolites cannot stay in the hair for a long time. They do have an expiry date, but differs from one drug to another. Let us sneak a peek into the detection periods of hair drug test for different drugs.

Hair Drug Test Detection Periods for Different Drugs

In the below tabular column, you can identify the different time period that the hair drug test would take to detect the drug metabolites.


Hair Sample Detection Period


Maximum of 2 days. The hair drug test cannot accurately find out the drug presence after 2 days of intake of alcohol.


About 90 days, varies for different brands


About 90 days


Maximum of 90 days


From 30 to 90 days, varies for different brands

Crystal MAMP

Maximum of 90 days


Maximum of 90 days


Up to 90 days


Up to 90 days

These are some drugs that are stored in the hair follicles and can be easily detected for an extended period of time.

Now that you are aware of the detection period, have you ever wondered how the hair drug tests are conducted? The fact is, if the tests are so accurate, the tests would definitely be complex.

How Does The Hair Follicle Drug Test Work?

The hair follicle drug tests work similarly to other tests. The hair sample is collected only during the test to prevent tampering or fraudulent practices. It may take place in a laboratory or in your workplace where they might collect your hair sample from your head or any other parts of your body for testing. Generally, hair sample is taken from the crown of your head, preferably 100 to 120 strands of hairs. However, if you do not have enough amounts of hair on the head for sample, then there are chances that they would collect hair from other parts of your body.

Hair follicle drug test involves two methods of testing – ELISA and Gas Chromatography. ELISA is a preliminary test that helps the tester to identify whether the person had taken the drugs for the past 90 days. It takes only 24 hours to identify the result. If it is negative, you are free from drug usage. If it sounds positive, then a confirmatory test using gas chromatography is done. This is a confirmatory test to determine the presence of drugs in your body. If it is positive, then it confirms that you are taking drugs and necessary action will be taken.

Considering the accuracy, the hair drug tests are 90% accurate in their indication of a person’s intake of drugs. If you have applied dye or color to your hair, you can still pass the hair drug test because there are fewer chances that the dye will enter into your hair from outside. In that case, various views are prevailing on the Internet about passing the hair drug test. Among them, only a few are legitimate.

One sure thing is that hair drug tests are difficult to cheat, but there are some hair drug test based myths and facts that are pretty familiar among the crowd. One such epic thing is that if you shave your head hair, you can escape from the drug test. As we have already discussed, if your head hair is shaved, the laboratory can take hair from other parts of the body. That can make things more critical because body hair can retain the drug for a longer time compared to the head hair.

You can try to escape the hair drug test if you are aware of the drug metabolites in your hair before any forthcoming test. There are certain testing tools like PDT-90 Hair Drug testing kit that can help you to determine drug presence in your hair before the actual drug test.

Final Words

It is irrevocable that hair follicle drug testing has arrived as enlightenment in the world of drug testing. The presence of drugs in the body is not a crime unless it is in the acceptable amounts; the hair drug tests reflect the same. From the above detection duration chart for different drug substances, you may have known about the hair drug test accuracy, detection time and its efficiency. If you are free of drugs and if your drug test is on the cards, there is nothing to worry. But if you are an occasional or regular drug abuser, it is time to clean yourself off the drug accordingly.

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