Effective troubleshooting for a diabetic small animal patient starts with the initial diagnosis of diabetes. Preempting trouble with a thorough and complete history, physical examination, laboratory assessment, and extensive and thoughtful client education before discharge, are crucial first steps toward avoiding trouble altogether. As problems arise, careful consideration of the many variables that contribute to effective diabetic control is necessary. As monitoring strategies evolve and treatment options expand, the clinician's ability to accurately assess and adjust the glycemic control in his or her troubled diabetic patient improves. Common causes of trouble in diabetic patients are reviewed and various strategies for the diagnosis and management of these disorders are discussed in this article. Every effort was made to draw from recently published reports of clinical cases. Few diseases will tie together owner, patient, and therapy as intimately as diabetes mellitus, and few problems will be solved without fully considering all potential factors.