67 citations,
May 2013 in “Therapeutic drug monitoring” Wait 4-5 weeks after drug use before hair testing and cut hair into three segments to confirm single drug exposure.
30 citations,
March 2012 in “Journal of Analytical Toxicology” THCCOOH levels in hair decrease from root to tip and don't match well with self-reported cannabis use.
September 2023 in “Scientific reports” Segmental hair analysis can track testosterone over time but needs adjustments for sex, hair color, and washing frequency.
July 2022 in “Research Square (Research Square)” Hair analysis can somewhat track past testosterone levels but is influenced by factors like hair washing, growth rate, sex, and hair color.
20 citations,
October 2017 in “Drug testing and analysis” Drugs localize differently in hair strands based on their properties.