In order to really understand the hair follicle testing process, it’s important to be familiar with standard drug detection levels.

Contrary to folklore, your sample is not going to be sent to some CSI lab where they are looking for even a single molecule of drugs in your system.  Tests like that are not feasible due to technology, resource, and financial limitations.

Instead, what the drug testing industry uses is standard drug detection levels (aka Level of Detection – LOD).  This gives the industry some uniformity in terms of their test results and also represents a level of detection that current technology and financial constraints deem reliable.

Most people are not aware of this but there are actually two commonly used testing methods which are used in drug testing.  The enzyme-linked immunosorbent assay (ELISA)  is the most common method of testing and, really, the only one you need to be concerned with.

The reason that we focus on the ELISA standard drug detection levels is because most testing laboratories will perform the ELISA test first and only if drugs exceed the Level of Detection will they then be tested using the much, much more accurate form of drug testing, gas chromatography–mass spectrometry (GC-MS).

If your sample exceeds the standard drug detection levels with the ELISA test the lab will then perform a GC/MS test on the sample to determine precise levels of drugs in the sample.

The GC/MS test is expensive which is why it is only used AFTER your sample has been determined to exceed the standard drug testing levels in the less expensive ELISA test.

The chart below illustrates why this is a big deal when it comes to passing a drug test.


As  you can see, the for marijuana, the standard drug detection levels are 1.0 pg/mg using the ELISA test and 0.1 pg/mg using the GC/MS.  That’s a huge, huge difference.

You don’t need to beat both.  You just need to pass the ELISA test.  If your sample contains less than 1.0 pg/mg of THC metabolites, the GC/MS test is not even performed.

Pass a Hair Follicle Drug Test