Dr. Lukejohn Day is the UCSF Health System Chief Medical Officer. He previously served for five years as the Chief Medical Officer for the Zuckerberg San Francisco General Hospital and Trauma Center (ZSFG). In his role at UCSF Health, he is the key physician leader for developing and implementing medical care policies throughout UCSF Health, ensuring standardization of medical care practices and procedures across the health system, and enhancing the interactions between inpatient and outpatient services. He is a practicing gastroenterologist and a Professor of Medicine at the University of California, San Francisco School of Medicine. His research interests have focused on developing and implementing efficiency models for improving healthcare delivery and quality in large healthcare systems. Additionally, he has performed impactful and influential research to understand drivers of efficiency and quality for performing endoscopic procedures.

He is a member of the Oglala Lakota Nation in South Dakota. He is serving a two-year term as the President of the Association of American Indian Physicians (AAIP) and has been an AAIP governing board member for over a decade. He has published extensively on colorectal cancer screening disparities that exist for American Indians/Alaskan Natives, as well as on strategies for how to increase the representation of American Indian/Alaskan Native physicians in healthcare, especially within gastroenterology.