Diabetes mellitus is a common endocrine disease in cats. While type 2 diabetes is the most common form seen in cats, other underlying causes may contribute to insulin resistance. Guidelines for diagnosis vary and often do not take into account prediabetic cats. The goals of treatment are to maximize the chance of remission, while minimizing the risks of hypoglycaemia. The first part of this webinar series presents the pathogenesis and diagnosis of diabetes in cats and well as an introduction to current treatment and monitoring recommendations.