Forensic Alcohol Calculations in transgender individuals undergoing gender-affirming hormonal treatment

ABSTRACT There are an increasing number of individuals undergoing gender-affirming hormonal treatment (GAHT) to treat gender dysphoria. Forensic alcohol calculations require knowledge of the sex of the individual but this may disadvantage trans people as research has demonstrated that there are physiological changes in individuals who are undergoing GAHT. Using previously published studies on total body water (TBW) in cis individuals and the known changes in lean body mass and hematocrit in trans individuals, it is possible to revise the rubric for the estimation of TBW in trans individuals. We propose these revised equations are used for transgender individuals. When using these revised rubrics, we determined that for trans women the use of the cis male (sex at birth) anthropometric TBW equation only gives a small underestimation of TBW (0.9%) compared to the underestimation (−17.7%) of TBW using the cis female (affirmed gender) TBW equation. For trans men the use of gender at birth (cis female) TBW equation gives the largest disadvantage, underestimating TBW by -10.8 % compared to the affirmed gender (cis male) TBW equation that over estimates TBW by 6.6 %. For this reason, we recommend that if the sex at birth of an individual is not known or disclosed, any forensic alcohol calculations in the report are made assuming that the gender declared by the individual is their sex at birth. HIGHLIGHTS Large number of people taking gender-affirming hormonal treatment (GAHT) around the world Total body water is altered in individuals taking GAHT Forensic alcohol calculation results are affected by GAHT Recommended that in an individual undergoing GAHT revised Watson equation used Forensic alcohol reports state assumption that individual is cis (unless sex at birth is known)