What Is a Continuous Glucose Monitor (CGM)?

A continuous glucose monitor (CGM) is a small, wearable device that continuously checks your blood sugar (glucose) levels (BGLs) without the need for daily fingersticks. However, many CGM manufacturers still recommend cross-checking your BGLs with a blood glucose meter (BGM) before you make insulin dosing decisions.

It’s important to keep in mind that BGMs and CGMs technically measure different things, which explains why readings may not always match, though they shouldn’t vary substantially. Instead of using blood, CGMs measure glucose in the fluid under your skin. They show your current trending level and whether your levels are rising, dropping or holding steady. In comparison, a BGM will only give you a flat number, a single moment in time.

Whereas CGMs let you see the road ahead—empowering you to decide how you travel down it, BGMs give you a quick snapshot with no clear visibility through your windshield (so to speak).

With real-time alerts, phone graphs and helpful insights, CGMs help people with diabetes (PWD) (and some members of the general public) make better choices about food, exercise, stress management and medication. 

They can also help you safely and effectively meet your A1C and time-in-range targets! So let’s talk about exactly how they get the job done.

How do CGMs work?

Different CGM brands work in unique ways, but they tend to share several common features. The Senseonics Eversense 365-Day CGM stands out for its implantable design, so most of the details below won’t apply to it. If you’re curious about Eversense-specific features, talk to your healthcare provider (HCP) or explore the manufacturer’s website.

Most CGM sensors are made of three main components:

• A sensor (a thin filament, wire-like piece) that sits just under the skin: senses/measures the BGLs in the fluid around your cells.
  
• A transmitter that sits above the skin: snaps onto or is built into the CGM sensor and transmits data, via bluetooth, that translates into your blood glucose values.
  
• A receiver, like your smartphone or a handheld device: receives your blood sugar data and shows you what it is. Note that if you do not rely on a mobile phone or trust one for your diabetes care, CGM manufacturers must provide a physical version. Check with your insurance to verify this.

A CGM sensor is usually inserted with a simple at-home applicator that uses a fine needle. Inserting a CGM sensor is quick, simple and often painless. Sometimes you might hit a spot that makes you bleed (lovingly known within the diabetes community as a “gusher”)—that’s why it’s so important to rotate your injection sites, which we cover later in this guide. That may happen the longer you live with diabetes, but rest assured, when this happens, it usually just takes a bandage and a call to your manufacturer to get a replacement! 

Inserting a CGM sensor typically takes just a few minutes and can be done at home. The needle retracts immediately, leaving the sensor in place. The transmitter remains visible on the skin and is secured with adhesive. Many sensors can be worn for 7 to 15 days. Wear time varies by device. If it falls off before the wear period is up, that’s a good reason to call your manufacturer for a replacement, too! Don’t be shy about it. You paid for the medical device and are entitled to ask for a replacement if it fails.

What’s the difference between standard CGMs and an implantable one?

Before we share which CGM options are available today, we don’t want to gloss over the differences between Eversense 365-Day CGM and the others listed below too quickly, especially if you’re wondering whether it could be right for you!

The main differences between Eversense and other CGMs are:

• It requires a yearly in-office procedure to use, which can be attractive versus changing your sensor at home yourself every 7 to 15 days.
  
• It is implanted and not removed by the person with diabetes—a certified healthcare provider must do it. While certified providers have expanded over the years, access to them remains sparse compared to the ease of doing it yourself at home.
  
• It requires fingerstick calibrations, while some CGMs only allow for factory calibrations.

What CGM options are available today?

CGM brands and models available in the US today include:

• Dexcom G7 CGM (10 day and 15 day)
• Dexcom Stelo OTC CGM
• Abbott Freestyle Libre 2 Plus CGM
• Abbott Freestyle Libre 3 Plus CGM
• Abbott Lingo OTC CGM
• Abbott Rio OTC CGM
• MiniMed Simplera CGM
• MiniMed Instinct CGM
• MiniMed Guardian 4 CGM
• Senseonics Eversense 365-Day CGM

Remember, the only implantable option on this list is Eversense, and options vary by region. If you are viewing this site from another country, speak with your healthcare provider about options that apply to you, as they may differ from those listed. Eligibility and recommendations vary by product. It’s always best to speak with your healthcare provider about what might be the best fit for you and what might not be suitable, such as whether a CGM is appropriate for a small child.

On a similar note, many other OTC CGM products exist if you do a quick Google search, but it’s a buyer-beware market. Those products are not intended for people who use insulin, which requires broader low and high blood sugar ranges than most OTC options provide. 

However, some community members may struggle to afford options that should be covered by insurance and may turn to them anyway because something is better than nothing. While not officially recommended by Beyond Type 1 or healthcare professionals, this choice is certainly understandable.

Where can you place CGMs on your body?

CGM sensors can be placed on various areas of the body, including:

• Upper arms
• Abdomen
• Upper thighs
• Upper buttocks

Some PWD go crazy and end up in totally unique places. Check out Beyond Type 1’s “sites you’re afraid to try” Instagram series for ideas that work but aren’t always officially recommended by manufacturers. Don’t blame a PWD for getting crafty or curious about new sites every now and then! One site on your body can only take so much, even if you’re great at rotating sites, which you should do often to avoid bruising, swelling, redness or pain when one site is used too often.

Most manufacturers recommend avoiding areas on your body that you bend frequently, or that might be irritated by clothing. Overpatches are often recommended as well to extend the life and wear time of your CGM. Some diabetes community members have even reported successfully and safely restarting a sensor that is still intact to stretch its life and save on costs. However, that’s not officially recommended by any manufacturer, HCP or Beyond Type 1.

Follow the lore at your own risk!

What are the main benefits of wearing a CGM?

There are so many benefits of wearing a CGM! 

Here are the main ones that help numerous PWD live better lives:

• You can see your blood sugar level anytime without finger sticks, so your poor, calloused fingers get a break!
• You can track the direction of your BGLs—no more stagnant readings like with BGMs!
• You can understand how and when your body reacts to food, activity, insulin, medication, hormones, stress, etc.
• You can connect it smartly with your insulin pump or smart pen through connected apps. Talk to your insulin pump manufacturer to learn what CGMs integrate with your tech and how to get them to “talk to each other” on your mobile phone or another device! Some independent apps are available to help support this, too.
• You can customize alerts for when your blood sugar is rising or falling.
• You can catch and treat low blood sugar (hypoglycemia) or correct high blood sugar (hyperglycemia) earlier.
• You can get a clearer, more complete picture of your time in range (TIR), glucose management indicator (GMI), and A1C data before your next visit with your HCP. 
• You can share your CGM data with your healthcare team, friends and family.

And honestly, these benefits only scratch the surface! They are a worthwhile and life-saving investment for millions of insulin-dependent people. 

How do you get a CGM? Start by asking for a prescription!

Getting started with a CGM usually requires a prescription. Still, some over-the-counter (OTC) options (like Dexcom Stelo or Abbott Lingo) are available to those who are struggling to get a prescription from their HCP and are the intended users (usually, those who are not insulin-dependent or using any sort of insulin). Ask your HCP about trying out a CGM. Many have sample CGMs from the manufacturers to share. 

If you are eligible for a CGM, try to get a prescription first, even if it requires navigating insurance loopholes, because that will help ensure coverage and potentially avoid out-of-pocket costs.

Here are some tips to help you find the best option for you that’s covered by your insurance:

• Discuss device options with your HCP to find the best fit for you.
• Check which brands are covered by your insurance, including Medicaid and Medicare.
• Medicare covers Dexcom and Abbott’s FreeStyle Libre CGMs for eligible individuals.
• For Medicare or Medicaid coverage, contact your state health exchange to confirm eligibility.

If you do not have insurance and/or cannot afford a CGM, see if you qualify for the manufacturer’s affordability programs, which can be found via their websites. Anyone who wants or needs a CGM shouldn’t go without one. Websites like DiabetesWise (DiabetesWise Pro for your HCP) can also help you figure out which options are the most likely to be covered by your insurance if getting a hold of them becomes a pain or more work than it’s worth.

Why CGMs make a huge difference in diabetes care

CGMs have transformed diabetes management, offering a simple and effective way to track your BGLs. From real-time alerts to personalized insights, CGMs empower you to make smarter health decisions, helping you live safely and achieve your goals with confidence. CGMs reflect a broader shift in diabetes care aimed at easing the day-to-day burdens of management.

While there is controversy over the general public using them to track health and performance, there was a time when BGMs were not available off the shelf. Some diabetes community members hope this trend inspires a push for greater affordability and accessibility in CGM coverage and less of a slap in the face that off-the-shelf options are sometimes more affordable than those covered by insurance.

Anyone who uses insulin or another blood-sugar-lowering medication should use a CGM. CGMs are a powerful and informative part of care that can significantly improve the lives of wearers everywhere! CGMs can save lives by catching lows before they become dangerous, recognizing chronic high blood sugar patterns before they lead to complications, improving blood sugar stability and creating peace of mind for PWD.