How Far Back Can a Hair Follicle Test Detect Drug Usage?

I have a job interview coming up and a friend of mine who works there said they do hair follicle drug testing before they hire you. I’m not much of a drug user, but I did partake a while ago at a party I was at. Is this something I should be worried about? How far back can a hair follicle test detect use?

Generally speaking, a hair follicle drug test can detect usage up to 90 days ago. By no means can it detect any usage within the past 90 days. For example, recent consumption tends to not show up on hair follicle screens. This is because it takes around a week or so for the metabolites to actually become embedded within the hair follicle. Also, consider that human hair grows at different rates from person to person. On average, human hair grows 0.5 inches per month. Most laboratories only analyze the first 1.5 inches of hair. If you do the math, it equals to roughly 3 months worth of hair.

In some cases a specimen cannot be collected from the scalp (usually due to baldness), so what happens is they choose another part of the body to take hair from (i.e. underarm, chest, leg, etc.). Because body hair tends to grow at a different rate than head hair, it can be said that body hair carries a longer detection window than head hair.

If you have hair on your head, and the party was more than three months ago – chances are everything will be fine. However, if you’re not entirely sure or you’re still skeptical about it, you might consider getting your own personal hair follicle test before going in for the job. The process is easy, and it’s an effective way to get the answers you need.