Continuous glucose monitoring (CGM) is the insertion of a sensor into the body’s fatty tissue which transmits blood glucose levels to a receiver as shown below:

It works by measuring the glucose concentration in the interstitial fluid (fluid found in between the body’s cells) as an approximate guide to the blood glucose concentration of the blood. Therefore, it is roughly 15 minutes behind the actual blood glucose concentration. This means it is less accurate after meals (blood glucose changes more rapidly) and is more accurate when blood glucose levels are stable. The Dexcom G5 (the CGM system that I use) also needs to be calibrated twice daily.

Below is an example of a CGM graph:

This CGM graph was produced using the Dexcom G5 system.

It is a very handy tool to have because in the short term, it notifies the user of low or high blood glucose concentrations so appropriate action can then be taken and it can also notify other people (for example, your parents). In the long term, it can help to identify trends in blood glucose levels over time. At Diabeasy, we use this data to help adjust your insulin dosing regimen accordingly.

An application that provides a lot more information than the Dexcom app is called sugarmate (https://sugarmate.io/). This is because it provides some other numbers which can help to get an idea of our blood sugar control.

This is a screenshot from the app and the important values to note are:

  • Estimated HbA1c- the HbA1c has been the most common test for blood glucose levels as it provides an indication of how much glucose has been bound to blood cells thereby acting as a measure for longterm glucose concentration over three months. However, it is not the full story as this number does not take into account variability which is how much the blood glucose concentrations vary.
  • Standard deviation- this is a measure of blood glucose variability and is an insight really only generated by the use of continuous glucose monitoring. The standard deviation reveals how much the blood glucose concentration varies and a very high standard deviation can have consequences on the body, even though the HbA1c may be in the suitable range.

Make sure to contact your health professional for them to set your targets and goals for your blood glucose levels as everyone has a different situation.