How Long Can Marijuana Be Detected In A Hair Testing After Last Use?

Posted on Tue, 1 Nov 2016

Medically reviewed by Ask A Doctor - 24x7 Medical Review Team

Tue, 1 Nov 2016 Answered on

Thu, 17 Nov 2016 Last reviewed on

Question : Hello

I will be taking a hair follicle test today for a job..only drug I've ever used is pot..I have not smoked since may 17 almost 6 months ago. should I be worried about failing?

Answered by Dr. Dr. Matt Wachsman (18 minutes later)

Brief Answer:
YES

Detailed Answer:
The detection is on the basis of when the hair was at when you smoked. My hair is chemically stimulated to grow fast... ONE inch a month, most people's hair grows slower. So, if I used pot ONE month ago, the hair at ONE inch out would be positive. In you, that would be 2 to 6 inches from the skull and if you show up with a bald head they are going to fail you. They are likely to find pot at 2 to 6 inches out from the skull. There is no way to make it NOT show. There are easy ways to make it be falsely positive (shampoo in pot).

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar