Continuous glucose monitor systems can consist of a disposable sensor placed under the skin, a transmitter connected to the sensor and a reader that receives and displays the measurements. The sensor can be used for several days before it needs to be replaced. The devices provide real-time measurements, and reduce the need for fingerprick testing of glucose levels. A drawback is that the meters are not as accurate because they read the glucose levels in the interstitial fluid which lags behind the levels in the blood