How Do Continuous Glucose Monitoring Devices Work?

With a biosensor and app, you can easily manage your glucose levels in real time.

Refrigerators that can tell you when you’re out of milk. Locks that can tell you when your front door is left open. Technology has reached a point where it can alert us to things that we are unable to see but need to know about.

When it comes to health, a continuous glucose monitor (CGM) is that technology. These biowearables give you minute-by-minute information about your glucose levels so you can figure out what you need to do to manage or improve your health and wellness.

We can’t tell you when food is about to expire in your refrigerator, but we can tell you about what’s going on inside your body — how it reacts to the food you eat, exercise, life’s daily stressors, and, for some biowearables, medications you take.

Here’s what you need to know about continuous glucose monitoring devices, whether they’re for managing a chronic condition like diabetes or improving your health and wellness.

How Glucose Monitoring Technology Evolved

Blood glucose meters entered the health scene in the 1970s. This method gave people the chance to see the invisible: You could see your glucose level through a drop of blood by sticking your finger.

While this method is still used today, CGMs, like our FreeStyle Libre systems and Lingo Glucose system, have been game-changers because they continuously measure glucose levels while also telling you additional information, like whether your glucose is on its way up or down.

“When you look at the results screen on your smartphone,1 it will show you how your glucose got to that point. And that is the first step to providing you with unique insights about how your food, exercise, stress, or, in some cases, medication is impacting your health,” said Marc Taub, divisional vice president of technical operations for Abbott's diabetes care business.

“The trend arrow that shows how quickly your glucose levels are changing and which way they are changing is important because you might do something very different if your glucose levels are moving quickly up or down or if they’re steady.”

In other words, CGMs put knowledge at your fingertips.

How Does the Biosensor Function in a CGM System?

Our biosensors are a small, circle-shaped piece of health tech that’s the size of a small coin.2 It’s placed on the back of your arm where it stays put with medical-grade adhesive. It has a thin, flexible filament that painlessly2 sits just below the surface of your skin.

The filament is about the same width as three human hairs — and it’s where most of the magic happens. The filament on the biosensor reads your body’s interstitial fluid, which is the fluid that bathes your cells and brings them the nutrients they need. Our biosensor technology can translate the amount of glucose in your body and send that information to a phone or reader through Bluetooth every minute.

CGM Systems Go Beyond Wearables

“You can't yet measure glucose accurately with a device that sits on the skin’s surface, which is essential because false readings can lead to confusion, misdiagnosis or incorrect treatment,” says Taub.

When a device is sitting on top of your skin, it's limited to taking readings from the outside of your body. This can work if you’re interested in understanding your heart rate or body temperature. However, tracking your glucose means you need to go beyond the skin’s surface because accuracy and precision are critical when you’re using that information to dose insulin or make personalized decisions about your health. Unlike smartwatches and other wearables, biowearables give people the accuracy they need, every minute, because they can directly read biomarkers inside your body.

To understand what your body is telling you, you need a team of “translators.” The biosensor part of a biowearable sends data to a smartphone app, providing real-time readings and visibility into your body’s reaction to different activities throughout the day. In other words, the biosensor and app act like a GPS map showing you precisely where you’ve been, where you are and where you’re going. You can adjust your route, or health habits, so you can get to where you need to be.

The interstitial fluid is like a pool of information that you can read when you have the right tools. It’s the fueling station for cells, so the biomarkers there are especially helpful when trying to understand how what you do and how and what you eat affect your overall well-being. Just like how your body’s processes never sleep, your biosensor doesn’t rest either, taking measurements (even if you’re sleeping). That provides data around the clock, ensuring you know where your glucose is in real-time, which isn’t available with fingersticking.3

Continuous glucose monitoring technology has moved beyond fingersticks that can only tell you what your glucose levels are at a single point in time. Today, these types of biowearables give you real-time data, directly from your body.

That’s personalized health, powered by CGMs.


1 The FreeStyle Libre systems apps are only compatible with certain mobile devices and operating systems. Please check the Support section of our website for more information about device compatibility before using the apps. Use of the FreeStyle Libre systems apps may require registration with LibreView.

2 Haak, Thomas, Hélène Hanaire, Ramzi Ajjan, Norbert Hermanns, Jean-Pierre Riveline, and Gerry Rayman. "Flash glucose-sensing technology as a replacement for blood glucose monitoring for the management of insulin-treated type 2 diabetes: a multicenter, open-label randomized controlled trial." Diabetes Therapy 8 (2017): 55-73.

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.


The Lingo Glucose System is intended for users 18 years and older not on insulin. It is not intended for diagnosis of diseases, including diabetes.

The Lingo program does not guarantee that everyone will achieve the same results as individual responses may vary. Consult your healthcare professional before making changes to your diet or exercise regimen or if you have an eating disorder or a history of eating disorders.

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