Dr. McKenzie has been a small animal general practitioner for twenty-five years. He is a past President of the Evidence-Based Veterinary Medicine Association, and in 2015 completed his MSc in Epidemiology at the London School of Hygiene and Tropical Medicine. He has taught veterinary students, written a monthly column for Veterinary Practice News magazine, and in 2019 published a book for pet owners and veterinary professionals—Placebos for Pets? The Truth about Alternative Medicine in Animals. Since 2021, Dr. McKenzie has served as Director of Veterinary Medicine for Loyal, an animal health company developing therapies to extend healthy lifespan in dogs.