Continuous glucose monitor

A continuous glucose monitor (CGM) is a device used for monitoring blood glucose on a continual basis by insulin-requiring people with diabetes, e.g. people with type I, type II diabetes or other types of diabetes (e.g. gestational diabetes). A continuous glucose monitor consists of three parts: a small electrode placed under the skin, a transmitter sending readings at regular intervals (ranging from every 1 to 15 min), and a separate receiver. Currently approved CGMs use an enzymatic technology which reacts with glucose molecules in the interstitial fluid generating an electric current. This electric current (proportional to the glucose concentration) is then relayed from a transmitter attached to the sensor out to a reader which displays the data to the patient. Traditional fingerprick testing of blood glucose levels measures the level at a single point in time. CGM use allows trends in blood glucose to be displayed over time. Some CGM devices have to be periodically calibrated by users with traditional blood glucose measurements, while some do not require user calibration. CGM is an increasingly adopted technology which has shown to have benefits for people with diabetes. Some studies have demonstrated reduced time spent in hypoglycemia or a lower glycated hemoglobin, both favorable outcomes. A Cochrane systematic review found that there is limited and conflicting evidence of the effectiveness of continuous glucose monitoring systems in children, adults or patients with poorly controlled diabetes. However, the use of continuous glucose monitors appears to lower hemoglobin A1c levels, more than just monitoring through capillary blood testing, particularly when used by individuals with poorly controlled diabetes together with an integrated insulin pump. However, there are important limitations: CGM systems are not sufficiently accurate for detecting hypoglycemia, a common side-effect of diabetes treatment. This is especially problematic as some devices offer alarm functions to warn of hypoglycemic episodes and people might rely on those alarms.