How long do the sample hairs have to be?

The hair sample should not be longer than 1.5 inches and can be as short as 1/8th inch if the person has buzzed hair, for example. The longer the sample length, the further back in time we are analyzing. Ideally, we want the more recent information. For a first hair analysis, 1 to 1 1/2 inches is fine (we find a ruler is helpful — some people accidentally send us hair samples 3 inches or even longer). For a repeat (progress) hair mineral analysis, you may want to use only an inch or less of hair that is closest to the scalp so that we have the most recent information and can see the more recent changes.