Impact of Gender Identity Field in the Veterans Health Administration Electronic Health Record, 2016‒2023

<b>Objectives.</b> To distinguish differences in physical and mental health between transgender and gender-diverse (TGD) veterans identified via diagnostic codes, self-identification, and their combination. <b>Methods.</b> We used sociodemographic characteristics and physical and mental health diagnoses for TGD veterans receiving care in Veterans Health Administration (VHA). <b>Results.</b> Among the cohort of 12 745 TGD veterans, 69.3% were identified solely using self-reported gender identity data, 23.4% were identified using only TGD-related diagnostic codes, and 7.2% had both TGD-related diagnostic codes and gender identity data in their medical record. TGD veterans identified using self-reported gender identity data were younger and more racially and ethnically diverse compared with those identified with only diagnostic codes. Across nearly all independently examined health conditions, TGD veterans identified via self-reported gender identity were at lower risk compared with those identified via diagnostic codes. <b>Conclusions.</b> Inferences drawn from studies of TGD veteran health may be significantly impacted by choice of methodology for defining the TGD veteran cohort. New analyses using self-reported gender identity data, as opposed to diagnostic codes, are critical to understand the health of this population within VHA. (<i>Am J Public Health</i>. 2025;115(3):403-413. https://doi.org/10.2105/AJPH.2024.307920).