If you work in an industry where drug testing is required, or have a job where they test you intermittently, it turns out that blood is one of the least effective tests for finding out about the rate of usage. For those one-time users, blood will stop being positive after about 24 hours. For those regular users who use one to five times a week, blood tests will remain positive for up to seven days. However, blood testing requires the use of a Phlebotomist, which is expensive, and most people don’t like being poked with needles.
However, it turns out that just for marijuana, the urine is an excellent test for determining regular use. One use of marijuana will last about seven days in the urine. However, for regular users, use may show up to 100 days after last use. This makes it hard to disguise the use of marijuana from your employer or other testing agency. So, as you might guess, urine testing has become the predominant testing for marijuana. Both urine and hair test for a marijuana metabolite known as THC-COOH. The more expensive and less often used Blood tests for THC levels, the active ingredient of marijuana.
The newest method of testing for drugs began in the 70’s, hair follicle testing. It turns out that a strand of hair grows for years and presents a true picture of the body during this time. While hair follicle testing has had some very interesting applications for the study of older civilizations and historical persons, it is not good if you have been a user and have a job that requires a clean record. Simply put, hair is a permanent record that can’t be altered by any known substance at this time. It turns out that your hair can be your worst enemy.
Hair is tested in the lab by the use of radioactive immune antibody testing. This test is impossible to alter in the hair. Positive tests are confirmed by spectrographic analysis as well, to rule out any possible lab contaminants. The hair is taken from the scalp, cut in a length of 1.5 inches. This provides a record of the last 90 days as hair grows about ½ inch per month. Studies have been done with hair analysis, but there is no correlation to level of usage when testing with hair. The hair will simply show the presence of the drug. With opiates and other products, hair can also show that degree of usage. However, if a longer time length is desired, a longer hair can be used for testing. So, hair can show marijuana usage months longer than urine testing. Urine testing is more specific for level of use, however.
What if you keep your head shaved?
Well, sorry to say, but body hair can also be tested. Due to the slow growth of body hair, body hair can only test for usage in the last calendar year. So, your hair can still be your worst enemy as many jobs that use this level of testing may expect zero usage results.
It is almost impossible today to hide marijuana usage from hair follicle drug tests. If there is some doubt about one type of test result, some jobs now require that the test subject to agree to provide other types of samples to clarify the test result. So, while a one-time use will not sink most people, anything approaching medium or even semi-regular use will be picked up by any qualified laboratory. Today’s testing is very accurate and evolving. Our best advice is to use avoid a job that requires hair follicle drug tests if you’re a regular smoker. If they test with urine though, there are many different beverages and pills that can help you pass. Be sure to read our post on The Best Tips for Passing a Drug Test after Smoking Weed