To fail a hair follicle drug test does there have to be a certain number or amount of thc present or is it any amount that will fail you?

Positive test will: Once the test is positive means you had used the drug usually within a window of 90 days.

THC: In “Pharmacokinetics of Cannabinoids” by McGilveray IJ it is stated “Hair tests are more likely to detect regular than occasional marijuana use. One study found that 85% of daily users tested positive for marijuana, versus 52% of occasional smokers (1-5 times per week).