What is the difference between CGM and BGM?
Both BGM and CGM provide information about glucose levels.
The key differences between them are:
Measuring frequency. The frequency of obtaining glucose values differs when using BGM versus CGM. With BGM, a person with diabetes might test their blood sugar levels several times a day, typically before meals and bedtime, depending on their type of diabetes and medication. With CGM, the glucose levels are measured continuously. The glucose values measured by the sensor in the skin are transmitted every 5 minutes, and they are combined to create a glucose curve. This provides a complete picture of glucose levels for the duration that the patient is wearing the sensor
Measuring glucose levels in blood versus interstitial fluid. BGM and CGM also differ in terms of how glucose values are measured. BGM measures glucose in capillary blood drawn from the fingertips (or sometimes from other places, like the palm of the hand). The sensor of the CGM solution, by contrast, is placed in the skin, specifically in the fat layer below the skin (subcutaneous fat tissue). There, the glucose level is measured in the fluid between the cells (interstitial fluid)
The difference in the measuring site (blood versus subcutaneous fat tissue) is one of the reasons that BGM and CGM values do not match at any time point. BGM reacts more rapidly to changes in glucose concentrations than CGM as changes to glucose levels in the interstitial fluid take more time to manifest.