Drug tests don’t test for drugs.
Actually, sometime the native drug is included in the test. But most drug tests look for the metabolites of drugs. That is, they look for what a body produces in response to exposure to the drug, rather than the native drug. That way you know whether the drug was actually ingested.
We don’t test the hair follicle.
Erroneously referred to as “hair follicle” testing, hair is cut off at the skin. If head hair is not available, body hair can be used. Because body hair grows much more slowly, it can detect a longer history. Each half inch of head hair is about 30 days of history. They test up to 1.5 inches for a maximum of 90 days.
Split vs. Single Specimen
In urine testing, often a “split specimen” will be collected. Only one sample is tested, but a second, sealed specimen is collected in the event the donor wants to challenge the test results using a different lab.
It’s negative if it’s below the cut-off.
A “cut-off level” is a threshold. If the level of a drug is below the cut-off, it’s called a negative result. Lower cut-offs yield more positives. Most workplace drug test cut-off levels mimic those describe by the U.S. Department of Transportation.