Abstract The proposed diversity supplement extends the parent grant's research on magnesium (Mg) supplementation in patients with diabetes mellitus (DM) and heart failure (HF), examining its differential impact across diverse racial, ethnic, and gender groups. This research addresses the knowledge gap surrounding the safety and efficacy of dietary supplements, particularly in the absence of FDA approval and comprehensive post-marketing surveillance. Preliminary data from the parent grant's pilot study suggest that Mg supplementation may reduce HF risk in patients with DM and enhance outcomes in those with HF. Given the substantial impact of HF and DM on millions of Americans, further investigation is essential. The diversity supplement comprises three specific aims to investigate Mg supplementation's role in diverse subpopulations. Aim 1 focuses on patients with DM from the parent grant, investigating whether oral Mg supplementation is associated with reduced incident HF risk, varying by race, sex, and ethnicity, with sub-hypotheses examining differences among African-American, Hispanic, and male Veterans. Aim 2 concentrates on patients with incident HF, exploring the relationship between oral Mg supplementation and the risk of death and hospitalization among HF patients, considering diverse populations. Aim 3 seeks to understand provider and patient perspectives on self-reported consumption of over-the-counter Mg supplementation in the context of HF prevention and management. Aims 1 and 2 will be achieved by interrogating the Veterans Affairs (VA) national EHR data that includes over 2 million Veterans with DM and 1 million with HF with ~20 years of longitudinal data on Mg supplements, serum Mg, and outcomes. As for Aim 3, in identifying and recruiting participants for the provider group, we will employ a strategic snowball sampling approach, guided by local champions. This method will facilitate the formation of two distinct focus groups: one comprising patients and the other consisting of physicians. The findings generated by this proposed supplement will offer valuable insights into the disparities in HF incidence and outcomes among different demographic groups, particularly those defined by race, ethnicity, and gender, while shedding light on the potential influence of mg supplementation in mitigating these disparities. This research addresses a critical gap in cardiovascular literature and has the potential to inform targeted interventions for at-risk populations and promote health equity in the context of HF.