Hair testing is becoming more popular due to it can be used to show up to 90 days of drug use. When an individual consumes any type of drug, that substance enters their blood as metabolites. Those drug metabolites then are carried through your blood till they are filtered and deposited in your hair.
Hair drug testing is used to test for drug usage within the last 90 days. Hair testing uses 1-1/2 inches of hair, representing about 3 months worth of head hair growth growth. Hair on your head is used because it grows evenly at about 1/2 an inch a month.
After a drug is used, it takes around 7-10 days for the hair containing the drug metabolites to grow out of the head enough to be cut. That means hair test will not include the drugs used within seven days prior to the test.
At the collection center 50 to 120 strands hair will be cut off and sent to a testing center. At the testing center the hair the hair is dissolved using various chemicals solvents to free the drug metabolites that may be in the deep withing your hair. Once any drug metabolites are freed using the solvents, your sample will be tested by a (GC/MS) gas chromatography/mass spectrometry to test if any drugs are present in the sample.