What is a CGM and how can I use it to see how I’m doing on Mounjaro?

Continuous Glucose Monitors (Libre sensors, Dexcom) are small skin surface applied devices heels on for 10-14 days with adhesive and tie to a cell phone application via Bluetooth. A small & short filament goes into your skin and collects data about the blood glucose levels in the interstitial fluid & once a minute, reports the blood glucose number to the app. The app makes a line graph as time goes by to show trends in highs and lows, plus indicate how much time is spent in the target blood glucose range. This is referred to as time in the target range (TIR: Time in range)  and is defined be a blood sugar level of between 70-180. The goal is to spend as much time as possible in the target range. 


Additionally, across a week or two, the CGM can show your average blood glucose number. This number generally aligns to an estimated A1C. Users of CGMs can enter notes about what food they ate, if they exercised and at what intensity level and for how long. These devices are instructive for T2Ds to learn real time what different meals and activities are beneficial or harmful. Doctors offices can be permitted to see the information to assist in treatment plans.


CGMs have been internationally approved devices to use for treatment protocols and also for going-forward outcome goals for treatments in trials. One of the SURPASS-3 studies that was done was to see how well Mounjaro keeps patients’ blood sugar in the target range (it did very well).


“With the advent of new technology, CGM has evolved rapidly in both accuracy and affordability. As such, many patients have these data available to assist with self-management and their providers’ assessment of glycemic status. Reports can be generated from CGM that will allow the provider and person with diabetes to determine TIR, calculate GMI, and assess hypoglycemia, hyperglycemia, and glycemic variability.”

Glycemic Targets: Standards of Medical Care in Diabetes—2022 

Diabetes care, 2022