Dr. Nulsen earned his bachelor's degree from Georgetown University in Washington, DC. He earned his medical degree from the Icahn School of Medicine at Mount Sinai in New York City, and continued there for his residency in internal medicine, serving as chief resident. He completed his gastroenterology fellowship training at UCLA, where he was chief fellow. During training, Dr. Nulsen researched novel approaches to gastrointestinal bleeding and patterns of medication use in irritable bowel syndrome. He also worked with the American Gastroenterological Association to develop the Gastro Cards educational app. Dr. Nulsen practices general gastroenterology and has clinical expertise in colon cancer screening, gastroesophageal reflux disease, motility disorders, functional bowel disorders, colorectal disorders, colonoscopy, and endoscopy. He is a member of the American College of Gastroenterology and American Gastroenterological Association. He is board-certified in internal medicine and board eligible in gastroenterology.