Kim is a research physiologist, specialising in digestive disorders such as inflammatory bowel disease. She currently serves as Distinguished Professor of Medicine and was formerly Dean of the Graduate Division at UCSD. She is the Editor-in-Chief of The Journal of Physiology and a Past-President of the American Physiological Society.

Her research focuses on the transport and barrier properties of the gastrointestinal epithelium and how these are deranged in the setting of various disease processes. Her work is relevant to the understanding of diarrheal diseases, particularly those caused by infectious agents such as Salmonella, and also to the mechanism of action of probiotics.