I've got a hair follicle and urine analysis test for a government job in approximately 6 months. I plan on quitting the day after 4/20. If I fail this test I am indefinitely barred from any government job for life and my degree becomes worthless so it's not an option. I have been smoking weed continuously for 4 years now. I know your hair has to be a minimum of an inch and half so they can go back 90 days. I'm just not sure of how long it takes for the metabolites to leave the body. How long should I wait after quitting to shave my head?