This paper presents a critical review of continuous glucose monitoring studies that address accuracy, utility in assessing glucose variability, detection of hypoglycemia for improved metabolic control or reduced glucose variability, impact on quality of life, reduced fear of hypoglycemia, and applicability in helping patients to overcome their reluctance to intensify insulin therapy. This analysis can be used to delineate the evidence that is still missing when considering continuous glucose monitoring as an established tool in clinical practice and for reimbursement of the system and services.