Understanding Continuous Glucose Monitoring (CGM) Data

by | Nov 7, 2022

With considerable research confirming the effectiveness of CGM in managing both type 1 and 2 diabetes mellitus and improving the quality of glycemic control, the adoption of CGM is rapidly increasing globally.

Continuous glucose monitoring (CGM) technology is a device that allows diabetic patients to continuously monitor and regulate their blood glucose (BG) levels and to reduce adverse metabolic states.

CGMs act as a personalized diabetes management tool that generates a large quantity of data necessary for expedient data preparation and interpretation for best therapy outcomes. The collected data helps an endocrinologist evaluate a patient’s progress and recommend alterations to their routine as well as treatment plans.

However, patients can also interpret specific data without a physician’s assistance and manage their lifestyle accordingly. This is why adequate user education is essential to ensure patients can monitor and interpret CGM data, make informed decisions, reduce the challenge of daily management, and regulate blood sugar levels effectively. Here are a few such CGM data and how to understand them.

Trend Arrows

The trend arrows in CGM provide an easy understanding of the direction and speed at which your glucose values are changing. They let you easily understand what is going on with your blood sugar levels and how to respond.

Interpreting these trend arrows can be helpful with premeal insulin dosing, before and after exercise, before bed, and understanding how glucose levels will trend in the next 30 minutes. The trend arrows can also help analyze how food, activities, and/or sleeping patterns affect glucose levels. For example, if the arrow rises rapidly after a specific meal or drink, one can take a walk to bring it down. It also gives a clear idea of what types of diet can spike sugar levels and thereby calls for restrictions.

Key CGM Metrics

This “Time In Ranges” Bar show the percentage of time you spend in five specified glycemic ranges:

  • Time in Range (TIR): The glucose levels between 70-180 mg/dl
  • Time Below Range (TBR): The glucose levels below 70 mg/dl
  • Time in severe hypoglycemia: The glucose levels below 54 mg/dl
  • Time Above Range (TAR): The glucose levels above 180 mg/dl
  • Time in severe hyperglycemia: The glucose levels above 250 mg/dl

The goal of this interpretation is to increase the green bar and reduce the red bars. In other words, one should aim to increase the time in range (TIR) and decrease the time below range (TBR) and time in severe hypoglycemia.

Most CGMs have customisable features that can be set to notify of any highs or lows. You have to set your optimal range under the “Alerts settings”. These alerts enable greater control over glucose management, empower better diabetes treatment decisions, and help reduce hypoglycemic and hyperglycemic incidents.

The Average Recommended Targets For TIR, TBR and TAR

AGP Report


(TIRhub.com, 2022)

The AGP report displays a specified duration of CGM data over a single 24-hour picture, clearly showing the variation of glycaemic control in a colour-coded and eye-friendly way to support meaningful clinical assessment and decisions. It is the general standard of care for reporting CGM data, per the American Diabetes Association.

It is a single-page report with three parts: glucose statistics like time in range, an ambulatory glucose profile, and a daily glucose profile. Through this report, you can quickly understand the time you spend above and below your target glucose range.

Here is what each section means:

Glucose Statistics and Targets

This section displays general metrics, including average glucose, glucose variability, and the time in ranges. It also includes the dates and duration of days the report is based on and the percentage of time that the CGM was used to collect data.

Ambulatory Glucose Profile

This graph combines your glucose readings over a specified number of days to display your trends across 24 hours.

  • Black line: This indicates the median of all the readings. You will see half of your glucose values above the middle black line and half below.
  • The two black horizontal lines: Represents your target glucose range.
  • Dark blue area: 50% of your glucose values lie in this area.
  • Light blue area: 90% of glucose your values lie in this area. This percentage may differ between AGP reports.
  • Dotted blue lines: 5% of your highest and lowest glucose values are represented above and below this line.

Daily Glucose Profile

Each box shows your glucose pattern on a single day.

  • Yellow area: Events of high glucose (hyperglycemia).
  • Red area: events of low glucose (hypoglycemia).

Once the analysis is made, the goal is to adjust lifestyle, diet, exercise, routine, medication, and insulin dosing to aim and spend more within the time in range. This means to try and maintain the glucose levels in the 70 – 180 mg/dl target range while having fewer lows and extreme highs. The wider the shaded blue areas on your report, the more variability there is in the glucose levels.

It’s best to identify when the glucose levels are lowest and highest and what is causing it to create an action plan. Comparing current and past AGP reports can also help understand strategies that work and those that don’t in regulating blood sugar levels. It can give better insights for you and your diabetes specialist into what changes are necessary to improve glucose patterns moving forward.

Making CGM Data Interpretation Easy

Our GluCare.Health app gathers data from connected devices, such as Fitbit, CGM, or connected weight scale, and displays them in the app in a user-friendly way that is easy to understand. We aim to be a part of our patient’s diabetes management journey from day 1.

GluCare’s model of diabetes management uses an Integrated Continuous Monitoring (ICM) methodology. This uses CGM data as part of other important parameters to give continuous feedback to our patients to maintain and improve the percentage of glucose time in range.

We track and stay connected with our patients 24/7 remotely using both humans and AI-based machines, so they never have to feel left out. Our patients can also clarify questions through the app anytime. Our healthcare team, including endocrinologists, nurses, educators, dietitians and health coaches, will attend to your questions at their earliest.

This near real-time patient engagement allows our care team to suggest corrective and proactive actions based on the information received or trends observed using factors such as glucose readings, sleep hygiene, activity, food logging, compliance criteria, etc. This instant feedback drives patient engagement and education about glycemic variability and, most importantly, makes compliance in diabetes management easy.

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