Also known as urinalysis, this procedure requires that one provide a sample of urine. Either a test card is used on site for immediate results or the sample is sent away to a lab to undergo gas chromatography/mass spectrometry (also known as GCMS), high performance liquid chromatography or immunoassay analysis. Sample substitution or adulteration have become a significant issue in the United States due to the prevalence of synthetic and/or drug-free urine and a wide range of adulterants on the internet. Some people attempt to defeat a urine test by drinking copious amounts of water, however, a sufficiently diluted sample may be rejected due to its clear color. Samples that are too clear may be flagged and tested for specific gravity. If the sample fails the specific gravity test, the sample is rejected and the dilution is reported to the entity that ordered the test. Some diuretics and herbal extracts, such as goldenseal, are marketed as a quick "detox" from controlled substances, but their efficacy is questionable. Some types of urinalysis can even detect the use of these "detox" products. One of the methods to test for adulterants is to add some amount of an actual drug to a small portion of the sample and then retest that portion. If a masking agent is present in the urine, the resulting drug test will have a negative result despite the fact that a drug was added.
Hair testing is quite accurate and can go back normally 3 months
(6 months or longer possible with specialty tests),
showing any drugs of abuse used in the detection window. As hair grows out, any drugs used are encased in the hair shaft,
so the longer the hair, the longer back in the individual's drug history the lab can detect. Accredited hair drug testing labs, however,
only use hair within about 2.5–4 cm of the scalp, and discard the rest. With head hair each 0.5 inch (0.8 cm) corresponds to about 30 days.
This limits the detection history to about 90 days, depending upon the rate of growth of the individual's hair. Some people attempt to circumvent
this through shaving their heads. In the absence of the required amount of hair on the scalp, body hair can be used as an acceptable substitute. It
is also possible to use body hair to do hair drug testing, but since body hair grows slower, the head hair window of detection measures will not apply
to body hair.
Additionally, for pre-employment hair testing, the inability to obtain a sample may be grounds for not hiring the individual. Hair Testing labs are regulated by CLIA or SAMHSA (not FDA). There is a growing trend in major companies and law enforcement agencies to utilize hair analysis on account of its efficiency and reputation as the gold standard when considering test accuracy. This technology makes use of radioimmunoassay technology with subsequent confirmation by mass spectrometry.
Saliva / oral fluid-based drug tests can generally detect use during the previous few days. Saliva or oral fluid based drug tests are becoming more prevalent because of their convenience and the fact that they can not be adulterated. Furthermore, on-site oral based tests in particular enable the implementation of random testing programs, proven to be the most effective type of drug screening. Oral fluid based tests are as accurate as urine and can be obtained from quality suppliers in the United States. Testing is usually performed by employers, for either pre-employment, random, post-accident, reasonable suspicion, or return-to-duty testing. Oral fluid based testing most closely mimics results found with blood and is preferable for detecting on-the-job drug use or in post-accident applications in this case because the degree of intoxication can be approximated based on the amount of substance in the blood.
Detection in saliva tests begins immediately upon use: