Dr James Alexander is a Consultant Gastroenterologist at St Mark's Hospital and Imperial College Healthcare Trust, London and an Honorary Senior Clinical Lecturer in the Department of Metabolism, Digestion and Reproduction at Imperial College London. He is also the IBD lead at Imperial College Healthcare Trust. Dr Alexander completed his undergraduate medical training at the University of Cambridge and Imperial College. He was awarded his PhD for research on the role of the gut microbiome in colorectal cancer and he went on to be a NIHR academic clinical lecturer in gastroenterology at Imperial College London. He completed his specialist training in gastroenterology in the North West London region. He performs upper and lower GI endoscopy, and conducts general gastroenterology and specialist IBD clinics including complex and joint medical/surgical IBD clinics.

Dr Alexander's research interests include exploring the role of the gut microbiota in determining colorectal cancer and IBD pathogenesis, complications and treatment responses, as well as studying the impact of IBD therapies on immune responses to vaccination. He was the lead author on the British Society of Gastroenterology (BSG) position statement on COVID-19 vaccination for patients with IBD. He is a member of the BSG IBD Clinical Research Group and the BSG Gut Microbiota for Health expert panel. In 2023 he was awarded the British Society of Gastroenterology Young Gastroenterologist of the Year in Clinical and Translational Science.