Continuous Glucose Monitoring
Starting Out - 101 Series

A Starter's Guide to Continuous Glucose Monitoring (CGM)

Having diabetes is a full-time job. You have to monitor your diet, activity, stress levels, sleep along with simultaneously calculating and managing carbohydrate to keep tabs on your blood sugar levels. In this article, we explain what is a CGM and how you can use the data obtained to help you manage and navigate your journey towards diabetes reversal.

What is Continuous Glucose Monitoring (CGM)?

It is a process that continually monitors the glucose (sugar) in your blood through an external device that’s attached to your body, to give real-time updates on your blood glucose patterns and trends.

What is Blood Glucose Meter (BGM)

Blood Glucose Meters (BGM) measure glucose levels in your blood at a single moment in time and require deliberate action to get a reading,

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Difference between Continuous Glucose Monitor (CGM) & Blood Glucose Meter (BGM)?

Blood Glucose Meter(BGM) Continuous Glucose Meter (CGM)
A 'Finger-stick Blood Glucose Meter' (BGM) provides a measurement of the blood glucose level at a specific moment in time (when you prick your finger) A CGM typically generates a new glucose level every minute, and records the reading every 15 minutes for a duration of 14 days or 2 weeks.
BGM is similar to a photograph-providing a  single blood sugar "snapshot" CGM is like a video - providing a constant stream of information on glucose level, trends and overnight data

How does the CGM device measure glucose levels?

CGMs measure the body’s glucose levels in real-time by sensing the glucose present in tissue fluid (also called interstitial fluid) through a sensor placed on your skin and transmits those readings to a small recording device called receiver. The CGM device has 3 components: the Sensor, Transmitter, and Receiver.

  • The Sensor consists of a tiny probe that is inserted under the skin of the upper arm using a simple applicator. Once placed, the device continuously records your glucose levels throughout the day/night for a duration of 14 days.
  • The Transmitter sits on top of the sensor and is attached to an electrode that sends glucose information to a separate receiver or a smartphone app.
  • The Receiver displays real-time glucose level, whether blood glucose is trending up or down, and your overall glucose history.
  • AGP Report - The blood glucose reading from the CGM device is then converted into a standardized report called an Ambulatory Glucose Profile Report which gives a detailed picture of your 14 day readings and includes a summary of your glucose profile, daily glucose graphs and the times you measured above and below your target range.

What is an Ambulatory Glucose Profile Report?

Developed by the International Diabetes Center, an Ambulatory Glucose Profile (AGP) report, is a standardized way of reporting continuous glucose monitor (CGM) data. It is a tool that provides a simplified way to look at data on your blood glucose patterns and trends based on at least 7 to 14 days of CGM data.

What are the General & Specific benefits of using a CGM?

  • CGM plays a vital role when it comes to predicting your current level of metabolic fitness thus helps in positively influencing improvement of your future metabolic health.
  • It allows you to keep a real-time check on how your body is functioning by offering you instant metabolic data to make the necessary changes to your lifestyle and reduce the likelihood of a surprise diagnosis later in life.
  • CGMs are particularly useful after meals and overnight, as they record when glucose levels drop or rise below a preset threshold.
  • CGMs provide a good way to monitor time spent “in range” (time spent within a normal, pre-specified blood sugar range) for people that have trouble reaching and maintaining target blood sugar.
  • CGMs are particularly useful if you often have lows and are unaware of when they happen (hypoglycemia unawareness).

How can I use the CGM data to reverse diabetes?

The AGP report allows your healthcare team to assess blood glucose levels, trends and patterns thus helping identify the times of day when glucose levels are consistently low, high, or fluctuating. The general goal for individuals with diabetes is to have glucose levels stay within the target range of 70 to 180 mg/dL for at least 70% of the day, and spending less than 3% of their time in hypoglycemia (under 70 mg/dL). This information from an AGP report helps your doctor set relevant goals for your diabetes management by providing care that's more precise and effective.


At the end of the day any data is meaningless if it cannot be interpreted correctly or not used by a provider to aid in diagnosis and a more focused treatment approach. Remember, CGM is a personal tool and not necessarily a single aspirational target or range that is universal. Your individual goals will depend on your needs, dietary and lifestyle habits, comorbidities and complications. Based on your unique presentation and recorded CGM data, your doctor will educate you on how to interpret and use your data to make the appropriate decisions to achieve your blood sugar goals.


Is CGM accurate? 

Yes, CGM or continuous glucose monitoring machines are accurate. The tiny sensor within the arm takes the blood sugar reading every 5 minutes 24/7 till the device is worn. The readings are precise and are recorded in real-time. You can also calibrate the readings taken by your CGM with your glucometer to check the accuracy. 

How long does a CGM last?

The sensor device inserted into the body that takes the readings can be worn for 7-14 days. The graph can be downloaded on your phones and laptops and you can use that with your endocrinologist to titrate the insulin doses accordingly.

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