What is Continuous Glucose Monitoring?

The basics of CGM, how FreeStyle Libre portfolio works and what it means for people living with diabetes.

DIABETES CARE|Mar.29, 2024

Pardon us, but WTH is CGM?

It's a question you may be asking right now.

Many living with diabetes have become familiar with continuous glucose monitoring (CGM) as their tool of choice for managing their diabetes care. But for some — including those recently diagnosed with diabetes — glucose monitoring and CGM technology can feel a bit mysterious, maybe even overwhelming.

DW (don't worry), we're here to give you the 411. We're going B2B (back to basics) on all things CGM.

What is glucose?
Glucose is essentially sugar in your blood. When you eat, glucose levels may rise as food is broken down into simple sugars to act as fuel to keep our bodies running. That's where "blood sugar" comes from.

So, why does monitoring glucose matter?
When we eat, our bodies have to work to process the glucose we consume. Enzymes, with help from the pancreas, break down the food we eat, and our bodies tell the pancreas whether or not to release insulin to manage our rising glucose levels.

For people living with diabetes, the pancreas doesn't produce the insulin needed and/or the body's cells may not properly use the insulin being produced. That's where monitoring glucose becomes so important.

What is continuous glucose monitoring?
Our FreeStyle Libre portfolio tracks your glucose levels throughout the day so you can see the impact of the food you eat and the activities you partake in while knowing what care you may need. It'll alert you if your glucose levels are too high or too low.

It can help provide the information needed to manage serious health impacts that can come with conditions like hypoglycemia and hyperglycemia

How does continuous glucose monitoring work?
Our FreeStyle Libre portfolio measures glucose levels with a small sensor — the size of two stacked quarters — on the back of your upper arm that measures your glucose day and night for up to 14 days, providing ...

  • A real-time glucose result
  • An eight-hour historical trend
  • A directional trend arrow showing where glucose levels are headed

… right on your reader or, where available with your FreeStyle Libre branded iOS or Android app, so you can make informed daily decisions.

With the help of LibreLinkUp and LibreView1 in select areas, you’re able to share2 your glucose level information with loved ones or your physician as needed as you progress through your diabetes management journey.

If you’re looking for something smaller than two stacked quarters, our FreeStyle Libre 3 is the size of two stacked U.S. pennies – it's the world’s smallest, thinnest, and most accurate 14-day glucose sensor on the market. It also provides real-time glucose readings to a compatible smartphone without scanning.

The FreeStyle Libre 2 Plus is a 15-day glucose sensor. In the U.S., it’s authorized to connect to the Tandem t:slim X2 insulin pump. In other words, insulin can be automatically delivered to your body when you need it because the pump works with the sensor to adjust insulin dosing based on your glucose levels.

Where routine fingersticks3 would take blood to read your levels at a given time, CGMs continuously (get it?) read your glucose so you’re aware and alerted whenever4, wherever.5

That's the L&S (long and short) of CGM 101. With your glucose IQ raised a point or two, know that there are options for those living with diabetes to make informed health decisions, ASAP.


1 The LibreView data management software is intended for use by both patients and healthcare professionals to assist people with diabetes and their healthcare professionals in the review, analysis and evaluation of historical glucose meter data to support effective diabetes management. The LibreView software is not intended to provide treatment decisions or to be used as a substitute for professional healthcare advice.

2 The user’s device must have internet connectivity for glucose data to automatically upload to LibreView.

3 Fingersticks are required for treatment decisions when Check Blood Glucose symbol appears, when symptoms do not match system readings, or when readings are suspected to be inaccurate.

4 Glucose readings are not available during 1-hour warm-up, when sensor is too hot or too cold, when you see an error, "LO" or "HI" message, or no current glucose reading.

5 Sensor is water-resistant in up to 1 meter (3 feet) of water. Do not immerse longer than 30 minutes.

This story was originally published on May 26, 2022, and updated on March 29, 2024.


Products for prescription only. For Important Safety Information, please visit FreeStyleLibre.us.