This is why drug testing laboratories claim to be able to go back just 90 days. They are aware that their testing will grow progressively untrustworthy with time. Drug testing businesses limit their tests to a 90-day period by checking only 1.5 inches of your hair closest to the scalp. The remaining hair is discarded (for testing purposes).
Hair grows at about 1/2 an inch per month, so if you have a full head of hair, then the shortest a drug test can detect marijuana use is approximately 30 months.
The longer a drug tests can detect marijuana use. The more reliable the test is likely to be. There are several factors which affect how long your drug test can detect marijuana use: length of time since your last use, type of substance being tested for, and level of concentration in your system. It is possible to get a false negative result from a drug test, meaning that you would fail even though you do not use drugs. This could happen if you come into contact with drugs other than marijuana or if you drink alcohol during the test period. Some drug tests can detect marijuana up to 36 hours after use.
It is important to remember that drug testing companies cannot look inside your body to verify what has happened in the past. They can only check what is in your hair at any given moment. If you want to hide your drug use from your employer or clients, it is best to stop smoking or ingesting drugs well before your next drug test date.
90-day period Hair drug tests have the greatest detection time, detecting drug usage for up to 90 days. Depending on the medications used, a hair sample can sometimes be used to identify when drug usage began and whether it was ended. However, since drugs are not destroyed by sweating or other body processes, a positive result may indicate recent use as well as ongoing exposure.
30-day period A 30-day hair drug test has the ability to detect drug usage within the last 30 days. This method uses chemicals to pull information from the outer layer of each hair. Then, an analysis tool is used to look for specific drugs. Although this method cannot tell you how recently someone used drugs, it can reveal recent usage.
7-day period An 7-day hair drug test can detect drug usage in the past seven days. This method takes two samples: one at the beginning of the testing window and another at the end. If both samples come back negative, then it can be concluded that the user did not use drugs during that time frame.
The longer the hair, the better chance it has of showing recent drug use. However, there are factors other than length that can affect how soon after use a hair sample will show signs of drug involvement. Personal grooming practices such as coloring or cutting your hair can remove evidence of drug usage.
They can also supply synthetic urine or urine acquired from another person. While urine drug tests normally have a one-week detection window, hair follicle drug tests have a 90-day detection window. It can even go back a year depending on the length of the hair gathered. However, using this method will not produce as accurate results for recently used drugs.
Hair grows at a rate of about 1mm per month so with enough hair, you can find out when something happened more than six months earlier. Hair grows in bundles called fibers which are made up of cells called cortex cells and medulla cells. The cortex is much thicker than the medulla and gives it strength. Inside each fiber is an onion-like layer called the cuticle which protects it from damage and keeps its color. Under the cuticle is a second protective layer called the papilla which contains blood vessels that feed the hair. Next comes the cortex which is made up of live cells that continue to divide even after the stem cell that gave them life went back to being a stem cell. This is why it is possible for a hair to grow for several months after someone uses cocaine or other drugs that affect growth of neurons.
Cocaine and its derivatives are found in the hair of people who use it and those around them don't always know. For example, parents of young children may not realize that their kids are using cocaine until they notice their hair begins to thin out.
While the fact that hair drug testing has such a lengthy lookback time is an apparent plus, one disadvantage is that it cannot identify present impairment. Furthermore, its detection window begins around seven days ago. Thus, if you use drugs during that time, you will fail even if you are not using them at the time of the test.
Hair tests can also reveal whether you have recently used drugs even if you had stopped before your last appointment. This is because certain medications can remain in your system for several months after you stop taking them. Drug screening tests for hair typically check for amphetamines, barbiturates, benzodiazepines (such as Valium or Xanax), cocaine, methamphetamines, opiates, phencyclidine (PCP), and THC-COOH.
The longer the time frame of your hair sample, the more likely it is to show evidence of recent drug use. If you want to be sure that you won't pass a drug screen then we recommend that you wait until at least three months after stopping use before taking any more challenging tests. However, if you were using very small amounts of drugs intermittently over a long period of time, then your hair test results may not be accurate until much later. It all depends on how often you used drugs and for how long ago you stopped using them.
Drug usage can be detected in hair follicle drug tests up to 90 days before the test date. Drug use also can be detected in fingernails up to 60 days before the test date.
Fingernail growth is limited by a layer of tissue called the epithelium. This tissue grows back quickly after an injury, which explains why some people are able to grow their hands back after removing a nail. The epithelium also produces new cells daily, so it's very flexible and can withstand rough handling without damage.
Hair growth is limited by the same thing-the epithelium-but it doesn't repair itself as easily as the fingernail. This means that if you cut off one of your fingers, the wound will heal but the finger won't grow back. Hair also grows from the root, not just from the surface like fingernails. This is why people usually lose the same number of hairs each time they shave or cut their hair.
Because fingernails and hair grow deeper into your body, they're more effective than skin for storing drugs. However, both tissues repair themselves fairly quickly.
Hair drug tests have the greatest detection time, detecting drug usage for up to 90 days. While hair samples cannot tell how recently you used drugs, it does provide evidence of recent use.
In general, if drugs are used regularly, they will be found in your hair. Even after stopping drug use, traces often remain within the hair shaft for several months or longer.
Drugs can be classified as either direct or indirect acting. Direct-acting drugs affect the central nervous system (CNS) directly by binding to receptors in the brain and other tissues. Indirect-acting drugs affect the CNS by stimulating or blocking natural hormones that regulate hormone production, release, or action. Both types of drugs can be detected in your hair.
Direct-acting drugs include cocaine, heroin, marijuana (cannabis), psychedelic mushrooms, PCP (phencyclidine), amphetamines (speed), and gamma hydroxybutyrate (GHB). Indirect-acting drugs include alcohol, birth control pills, corticosteroids (anti-inflammatory agents), anticonvulsants (medications used to treat epilepsy), anorectics (food supplements), and thyroid hormones (for treatment of hypothyroidism).