Her career includes serving as Medical Director for the Kidney/Pancreas NIDDK intramural transplant program and at the Birmingham VA Medical Center and Section Chief of Transplant Nephrology at the University of Alabama at Birmingham. Dr. Mannon is a past president of the AST and is a deputy editor of the American Journal of Transplantation. She is the chair of Women in Transplantation, an initiative of the Transplantation Society, chair of the Policy and Advocacy Committee of the American Society of Nephrology, and co-chair of the Scientific Registry of Transplant Recipients Review Committee. She is a trustee of the Banff Allograft Pathology Foundation.

She was recently named a UNMC distinguished scientist for 2022. She is board certified in internal medicine and nephrology.