Guy has worked as a cardiologist on the North Shore since 1998, both at North Shore Hospital and in private practice at Waitemata Cardiology. He left Rosmini College for Auckland University where he did a Bachelor of Chemistry, followed by a medical degree.

After training in cardiology at Greenlane, Guy undertook additional training to gain particular areas of expertise. This included:

• Interventional Fellowship at Auckland City Hospital, learning angioplasty and stenting of narrowed coronary arteries
• Examination to become a Testamur of the North American Society of Pacing and Electrophysiology, gaining proficiency in the assessment of slow heart rhythms causing faints and funny turns, and in the procedure of pacemaker insertion.
• Advanced Fellowship in Cardiovascular Imaging at the Cleveland Clinic Foundation, learning the technique of echocardiography and applying it to patients with heart valve abnormalities and reduced pump function of the heart.

He has published scientific research in all these areas, but his focus is on taking good care of his patients .