Hair strand testing is done for a historical view of what has been taken in by someone. That is to say, it gives you information for what the person being tested has taken in from the last 30 to 90 days, depending on the length of hair being tested. You can use head hair for testing, cut as close to the scalp as possible, or body hair. Hair strand testing is looking for metabolites of the drugs that have been stored within the hair as it grew from the person’s scalp (or body).
Laboratories are also able to segment a head hair sample, which means that they cut it into sections A, B,and C with each segment giving a snapshot of drug use within a thirty day timeframe going back to ninety days from testing. Hair grows about .5″ per month so a sample of 1.5″ would show what had been taken in within the last 90 days.