CGM devices might be professional or personal

Test Quick Guide
Continuous glucose monitoring (CGM) allows diabetics to monitor their blood glucose levels throughout the day and night, reducing the number of fingersticks blood tests are required each day.
Glucose is the sugar that your body uses as its primary energy source. Food is converted by the body into glucose and other chemicals that enter the bloodstream. The pancreas generates the hormone insulin, which transports glucose from the bloodstream into the body's cells.
Diabetes is a dangerous medical disorder in which either the pancreas or the body's cells are unable to receive insulin. Inadequate insulin in the body and cells can result in excessively high blood glucose levels, which can harm the body's tissues and organs if diabetes is not controlled.

What does the test measure?

The level of glucose in the fluid between the cells, known as the interstitial fluid, is monitored continuously. Interstitial glucose levels are closely related to blood glucose levels.

CGM devices use a very small wire sensor that is implanted just under the skin of your belly or upper arm to measure glucose levels. A transmitter attached to the sensor wirelessly transmits this data to a dedicated receiver or a device such as a smartphone.