Dr. MacGregor received his DVM from Cornell University, College of Veterinary Medicine in 1998. In 1999, he completed an Emergency and Critical Care internship at Tufts University School of Veterinary Medicine. Dr. MacGregor was a staff veterinarian at Andover Animal Hospital and Sudbury Animal Hospital from 1999 to 2001.
Between 2001 and 2004, Dr. MacGregor was a resident in cardiology at Tufts University, School of Veterinary Medicine. He became board certified by the American College of Veterinary Internal Medicine in 2004. Dr. MacGregor joined the IVG network of hospitals in July 2008.