4-6 weeks of new growth is preferred for the HTMA test. The sample is that is needed is as close to the scalp as possible. If your hair dye has bleach or peroxide, you will have to either wait for new growth (or leave a hidden section un-dyed) or you can send fingernails or pubic hair. We encourage scalp hair though as that is the most accurate sample. The lab does not accept beard, armpit, or other hair.