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Drug hair test: detection time based on the length of the sample

The drug screening test by hair analysis is an increasingly used method to detect the presence of illicit substances. Its main advantage is its ability to go back in time, sometimes up to several months before the test. However, this ability depends on several factors, including the length of the hair sample and the growth rate of the hair.






Drug hair test: detection time based on the length of the sample

How does a hair drug screening test work?


The hair drug screening test is a quantitative test that measures the specific amount of drugs present in a hair sample.


It is a tool for assessing drug use, although it does not allow for accurately determining when the substance was ingested. The test only provides information about the amount of drug present in the hair sample at the time of analysis.


The principle of operation of this test is quite simple and is based on the physiology of hair growth. After being ingested, drugs circulate in the individual's bloodstream. As the hair grows, these substances are incorporated into the hair structure.


Therefore, a hair sample acts as a kind of "log" of a person's drug use. It provides an overview of drug use over an extended period, unlike urine or blood tests, which can only detect drugs over a short period. That's why the hair drug screening test is a method of choice for getting a more complete picture of a person's drug use.


Sample collection and type for hair drug screening test


For a hair drug screening test, the hair sample is usually taken from the scalp. Indeed, hair is generally preferred because it grows at a relatively constant rate and is less likely to be affected by external factors.


The collection is simple and non-invasive. A small sample of hair is cut at the base of the scalp, usually in a discreet area. Generally, about 100 to 120 hairs are needed for the test, which corresponds to a thickness of about a pencil.


It is important to note that the collection must be carried out correctly to guarantee the accuracy of the test. The sample should be taken as close as possible to the scalp and should be long enough to allow for accurate analysis.


If head hair is not available, it is possible to use other body hairs. However, it is important to note that the growth rate of body hair can vary considerably. Therefore, using body hair can affect the drug detection window.


Drug detection based on sample length


The ability to go back in time to detect several months of substance use depends on the length of the analyzed hair sample. Indeed, the longer the hair sample, the more extended the detection period. For example, a 3 cm sample can trace drug use going back about three months.


However, it is possible to perform tests on a sample for a total duration of 12 months, provided

that the sample size is at least 15 centimeters long.


The tests are carried out in several stages to ensure continuous evaluation of the sample. The laboratory divides and tests the sample in the following time segments:

  • from the beginning up to 90 days,

  • then from 90 to 180 days,

  • then from 180 to 270 days,

  • and finally from 270 to 365 days.


This period of time can be considered as a general average. However, it is important to note that this duration varies depending on the individual's hair growth rate.


Indeed, if the individual's hair grows faster or slower than average, the detection period could be respectively shorter or longer. Therefore, these individual variations should be taken into account when analyzing the results.


Does hair growth rate affect the hair drug screening test?


The rate at which hair grows is influenced by a multitude of different factors. On average, it is estimated that hair grows at a rate of about 1 cm per month.


However, this speed can fluctuate depending on several elements, such as age, general health status, diet, and even genetics.


For example, young, healthy people may find that their hair grows more quickly, while hair growth can be significantly slower in older people or those suffering from certain medical conditions. Additionally, a diet rich in essential nutrients can promote faster hair growth, while a deficiency in vitamins and minerals can have the opposite effect.


Buying a hair drug screening test online


Buying a hair drug screening test can be done very easily on the internet. The participant can buy the screening kit directly from the laboratory. The screening kit will then be sent home, allowing the participant to do his own hair sample collection.


It should be noted that laboratories generally offer different screening options depending on the type of drug sought. For example, some tests can detect the presence of cannabis, cocaine, amphetamines, opiates, or other substances.


There are two types of hair drug screening tests:

  • the anonymous test

  • the legal test


The anonymous test is private and the results are only for you. This type of test can be useful for individuals who want private and confidential drug screening.

For the legal drug screening test, the laboratory will ask you to provide your doctor's address.


The doctor will be in charge of receiving the kit, taking the samples, and verifying the participant's identity. The laboratory report for a legal test can be used for legal or administrative procedures. Therefore, it is important to choose the right type of test according to your needs.


What types of drugs can be detected with a hair test?


The drug screening test by hair analysis is extremely comprehensive and can detect a variety of illicit substances. Here are some examples of drugs that this test can identify:


  1. Cannabis: This is one of the most commonly detected drugs. The test can identify THC, the main psychoactive component of cannabis.

  2. Cocaine: Cocaine is another drug commonly detected by hair analysis. The test can identify cocaine and its metabolites, indicating recent or chronic use.

  3. Opiates: The test can detect a variety of opiates, including heroin, morphine, and codeine. Opiates are often detected in hair tests due to their widespread use.

  4. Amphetamines: This group of drugs includes substances like speed, Adderall, and methamphetamine. Hair analysis can detect these substances and their metabolites.

  5. Ecstasy (MDMA): Ecstasy is a popular synthetic drug that can be detected by the hair test.

  6. Phencyclidine (PCP): Although less common, PCP is another drug that the hair test can detect.


The drug screening test by hair analysis is a powerful tool for detecting drug use, capable of going back several months depending on the length of the sample. However, it is important to understand that detection depends on several factors, including hair growth rate, and that the test provides a quantitative measure rather than precise dating of consumption.

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