Continuous glucose monitoring (CGM) system is largely used in clinical practice in patients with type 1 diabetes and insulin-treated patients with type 2 diabetes. It is a needful tool for a more comprehensive assessment of glucose control. Patients can benefit from real-time information on current glucose, glucose trend, and hypo or hyperglycemia alarms. Healthcare can rapidly understand how much time patients spend in a good glucose range, hypoglycemia or hyperglycemia. Several clinical trials have demonstrated the benefits of CGM in reducing glycated hemoglobin, as well as the time spent in hypoglycemia, and increasing the time in range. CGM reduces the rate of severe acute complications and hospital admission improving the quality of life. Patients on insulin treatment and pregnant women are the perfect candidates for CGM. However, even patients on non-intensive insulin treatment or other therapies might benefit from CGM to gain and maintain reasonable glycemic control, and again improve the quality of life.