Dr. John Gahagan is a colon and rectal surgeon in Pleasanton, California and is affiliated with multiple hospitals in the area, including Stanford Health Care Tri-Valley and Stanford Health Care-Stanford Hospital. He received his medical degree from Wake Forest School of Medicine of Wake Forest Baptist Medical Center and has been in practice between 11-20 years. Dr. John Gahagan has expertise in treating colonoscopy, colon removal, among other conditions - see all areas of expertise. Dr. John Gahagan accepts Medicare, Aetna, Cigna, Blue Cross, United Healthcare - see other insurance plans accepted.