How Drug Tests Work for the Non-Scientist

What test you should order with pros and cons of each collection method.

How do drug tests work?

We get asked that question almost daily. The answer is really long…and often ends with the person that asked the question eyes glazed over.  So…to keep that from happening now and from you falling asleep or not finishing this article, let’s put the answer in terms that your client (non-scientist) can understand.

The simplest way to explain how a drug test works, is for you to understand that we are not looking just for the actual drug the individual took, but also what your body makes out of the drug they took.  Confused yet?  If you’re like most people, you probably are…drug testing can be very confusing.   But it is really fairly simple…Let’s start with a common drug of abuse.

The very popular Marijuana.  The substance in Marijuana that gets individuals “High” is a molecule named “THC”.  Most people are familiar with THC and know its connection with marijuana.  When you ingest THC through smoking or eating it, your body immediately starts to get rid of it…or processes it out of your system.  This is a really complex process that results in a new molecule being created by your body called a “Metabolite”.  Your body takes the THC in marijuana and creates a Metabolite called THC-COOH.  You can’t buy THC-COOH on the street.  The only way an individual is going to have THC-COOH molecules in their system, is if their body made it from THC they ingested. This works for all drugs.  All drugs have metabolites.  When an individual is getting tested for Marijuana use…the test is looking for THC and THC-COOH. It will be present in the individual’s urine, hair or nails.  When the test identifies the metabolite in their system.  The test confirms the individual ingested the drug.  It’s that simple.

So…How do we find and identify the Metabolites?  The urine, hair or nail sample is sent to a highly specialized lab that puts the sample under an extremely powerful microscope that uses a process called “mass spec/gas chromatography” to identify the drug or drug metabolite present in the sample. The mass spec/gas chromatography identification process is 100% accurate. There are no errors…When the mass spec identifies the THC-COOH metabolite in the sample.  It is confirmed that the donor is using Marijuana.  Without question.

The biggest question you have to answer is, “What kind of sample do you want to send the lab?”  For Legal applications, we recommend you tailor your choice based on the length of history and the type or types of drugs you are looking to identify.  There are three different types of samples or methods of drug testing that we recommend for legal applications.  Those are Urine, Hair, or Nail tests.  Which test you select is crucial to the application of the results.

Our recommendation for legal application is that you order both a Urine and a Hair or Nail test.  The urine will cover recent activity and the Hair/Nail test will provide a longer history of the donor’s drug use or lack of drug use. The combination of these two tests will insure you get a complete look into the donor’s potential drug use and will make it extremely difficult for the donor to adulterate the results.

The following is a brief description of each type of sample or test with the Pros and Cons of each one. Our hope is this will help you understand why we recommend the tests we do.


Urine or “UA” testing is the most widely used method of testing. In legal applications we recommend strict observation of the test with adulteration and dilution testing of the sample to prevent the donor from adulterating the sample.

PROs: Most drugs of abuse and prescriptions can be detected in urine within a few hours of ingest and some drugs can be detected for up to a month. Urine is easy to collect, is inexpensive and requires little to no notice for the donor.

CONs: Given the opportunity…Urine samples can be altered by the donor.  Some drugs can only be detected in urine for 24-48 hours with most drugs being un-detectable in urine within 2-3 weeks of abstention depending on use.


Hair testing is now seen as a powerful tool for the detection of drugs and is widely used in legal and employment applications.

PROs: Hair provides a long-term history of drug use up to 90 days from the date of collection. Hair is easy to collect, stable and easy to transport.  Hair is difficult to adulterate for the donor and requires little to no notice for the donor.

CONs: Drugs are detectable in hair at the rate of growth and it can take 7-10 days for recent drug use to show up in hair. Samples must be a minimum of 1.5 inches in length (scalp hair) and the donor may not have enough hair to provide a sample immediately, and could be required to collect body hair or scheduled for a second collection when their hair is longer. Donors can tamper with hair by cutting, or bleaching if given the opportunity. The sample site on the scalp may be visible until the hair regrows.


Nail testing is on the cutting edge of drug testing technology and has many similarities to hair testing with the advantages of greater stability and a longer window of detection. Technological advancements and greater usage have resulted in lower costs making nail testing more affordable. (same cost as hair at KT Health)

PROs: Nails provide the longest-term history available of drug use of up to 8-12 months from the date of collection. Nails are four times thicker than hair and capture more of the metabolites than hair resulting in easier detection. Nails are extremely difficult to adulterate and are simple to collect and transport with minimal impact to the donor (appearance).

CONs: Nails grow really slow. It can take up to 14 days for recent drug use to show up in the nails.  Samples must be a minimum weight and the donor may not have enough nails needed for an adequate test and may be required to return multiple times for collections which can elongate the testing process. Donors can tamper with nails by cutting them off if given the opportunity.

Instants or Dip

We don’t offer or recommend “Dip” testing for legal use.  But we get asked about them regularly. So, we thought we would include them in this discussion.

Instants/Dips are widely used for NON-Legal or employment screenings.  May be used if you are interested in recent drug use only.

PROs: Fast results. Most test show results immediately. Little to no training needed to administer.

CONs: Instant drug tests are not certifiable and are not recognized by the State of Missouri or the DOT for legal or employment applications. They tend to have a high level of Non-confirmable results when retested with SAMSHA level drug testing. Testing for adulterants or dilution is not available. Most drugs of abuse are only detectable for up to 24-hours after ingestion if at all. Prone to false positives. Results are un-reliable and not court admissible.

In our opinion…doing a drug test with-out SAMSHA certification and Legal admissibility is doing a drug test purely for entertainment purposes.

Hopefully, this article has given you a better understanding of what drug testing can offer you and your clients and why we recommend the type of tests we do.  If you have a question, or need assistant in selecting a test or tests.  We are here to help.