Dr. Leong is an Instructor in Medicine and Assistant in Medicine in the Division of General Medicine at Massachusetts General Hospital, Endocrine Division and Harvard Medical School. His work focuses on the application of type 2 diabetes and hemoglobin A1c genetics to public health, health disparities, pharmacogenetics, and clinical practice. His research uses multi-ethnic cohorts and biorepositories-linked with electronic health data to determine whether the genetics of diabetes and related traits can be used to predict health outcomes, drug responses, diabetes progression, complications and comorbidities. He also performs Mendelian Randomization studies to evaluate causal associations of diabetes and cardiovascular risk factors. He leads clinical studies aimed at recalling carriers of diabetes-related genetic variants to undergo detailed physiologic characterization.