Buying a Continuous Glucose Monitor

What is continuous glucose monitoring (CGM)?

Some people with diabetes measure their blood glucose several times a day. Perhaps they will conduct glucose readings before and after eating and in the morning when they wake up. But for those with more severe diabetes, it may be necessary to keep track of blood glucose all day long. That's where continuous glucose monitoring comes in. Using a continuous glucose monitor, diabetics can keep constant track of their blood glucose and can be alerted when their blood sugar needs to be addressed.

See Related: Best Sugar Substitutes For Diabetics

image of smartphone with glucose readout

How does a Continuous Glucose Monitor work?

In order for continuous glucose monitoring to work, a tiny sensor is implanted under the skin. This is often under the skin of the arm or belly. Every few minutes, this sensor will then measure blood glucose found in the fluid between the cells. These glucose readings are then sent to a monitor in order for the user to keep track of the blood glucose.

Who can use a CGM?

Generally speaking, if you are able to use a CGM system, you likely have Type 1 diabetes. While people with Type 2 diabetes do still need to monitor their blood glucose, they are sometimes able to manage their blood sugar with just diet and exercise or in some cases with the use of insulin. Type 1 diabetics, on the other hand are extremely rarely able to manage their blood sugar without the taking some form of insulin. It is for this reason that they are more likely to require a CGM system. Those who suffer from high blood glucose on a very frequent basis will be more likely to employ the use of a CGM system than those who are able to more easily manage their glucose levels.

What are the benefits of a CGM?

touching cgm sensor

CGM systems can help diabetics better understand their glucose levels throughout the day and the way in which their diet and exercise affects them. By using continuous blood glucose monitoring you will see how your glucose levels fluctuate, helping you to better plan your diet around your diabetes.

Using a blood glucose meter like this will also help you to reduce how often you will need to use needles for your glucose readings. You will also receive alerts warning you when your blood sugar levels are too high or too low, allowing you to take immediate action to address them.

What are the limits of a CGM?

Your continous blood glucose meter may not always be one hundred percent accurate, therefore, though you can reduce how often you will need to use a finger poke reading during your diabetes care, you should still conduct them twice a day to make sure your device is calibrated. These devices also take longer to detect changes in blood sugar, since they work at timed intervals. Whereas a stick poke is instantaneous.

How do I choose a CGM?

First and foremost, CGM devices can be very expensive. One of the first places you will need to start is in figuring out what your health insurance will cover and what the costs incurred will be. From there, it will be best if you focus on the features and the way the device works so you can determine if it will best suit your needs and ability to operate it.

CGM For Athletes

installing cgm sensor with aplicator

Obviously, people with diabetes are those who will most likely be in need of a CGM device, but that does not mean they are the only ones who can benefit from them. Nowadays, athletes have started to employ continuous monitoring to keep track of their glucose trends while they are performing physical activities.

The body deals with glucose in different ways during physical activity, especially when you are active for long periods of time. Your glucose level will likely rise when you are first starting out and then should begin to drop when your body starts burning the glucose stored in the body as you continue with endurance training. Some athletes believe that active monitoring of their glucose level changes throughout physical activity or an extended training session will help them to better understand their body's needs when it comes to fuel and burning energy.

CGM for Weight Loss

We know that eating food, especially foods that are high in sugar, can cause the glucose level to rise. But there are more reasons that your glucose level could be higher than it should be. For example, if you are lacking in sleep or exercise, you might find that the level of sugar in your blood could go up in these instances, as well. Having constant blood glucose data helps people to see when their sugar levels are too high so that they can then work to lower them. Frequent high glucose can have an affect on the metabolism, so learning to keep your levels under control can have a direct impact on your ability to lose weight.

CGM for Gestational Diabetes

If you already have diabetes or are diagnosed with gestational diabetes, you might want to consider a diabetes care device that continuously monitors glucose numbers allowing moms-to-be to make treatment decisions based on accurate readings. Implanted under the skin, a small sensor measures the sugar in the blood throughout the day, updating the wearer of their glucose needs. Again, mothers with Type 1 diabetes are recommended to use a glucose monitor of this sort. FDA approval has not been currently give for the use of this type of glucose monitor for pregnant women, but these devices have been approved for diabetes monitoring during pregnancy in the UK and temporarily in Canada.

Ideal Blood Glucose Levels

Glucose levels under 140 are ideal, even if you have recently eaten. If you have been fasting, however, you would want to see glucose numbers at or below 100, preferably. Though you would want to see that 140 glucose number an hour or two after a meal, the typical glucose level that indicates diabetes is 200 or more. These glucose numbers are generally the same when looking for diabetes during pregnancy.

CGM systems

Now that you have some idea of what sorts of devices, functions, and features you need and have checked with your health insurance it's time to pick the right glucose meter! But where to begin? There is no lack of glucose meter options on the market, so let's give a quick review of the available devices and how they might help you make treatment decisions in your diabetes care.

Freestyle Libre

There are two versions of the Freestyle Libre, the FreeStyle Libre 14-Day System and the FreeStyle Libre 2 System. Both systems offer a calibration-free experience, 8-hour memory, 14-day lifespans, and easy sensor application. The main differences between these two devices are that the 14-day system does not feature alarms but is compatible with smart devices (like your phone) while the Libre 2 is meant able to used for younger patients from the age of four and up.

Dexcom G4

The Dexcom G4 is considered an excellent choice for those who often suffer from low blood glucose. This devices offers customizable alarms and a USB port to allow CGM results to be uploaded to another device, such as a computer or phone. A separate device acts a receiver and allows a 20-foot range. Patients in the US should be cautioned that this device no longer receives support and that accompanying app is no longer available for download.

Dexcom G5

The Dexcom G5 promises real time readings and the ability to easily switch between receiver or smart phone. Calibration is said to be possible through either device, as well. Alarms can be customized with 22 different sounds and will send notifications for high or low blood glucose. Unlike the G4, the G5 offers Bluetooth capabilities. However, just like with the G4 device, the G5 is no longer supported in the US and is no longer compatible with smartphone apps.

Dexcom G6

The Dexcom G6 transmitter sends data to either your smart phone or a separate device that acts a receiver. This device also offers a calibration-free experience with a one-button insertable CGM sensor. The CGM sensor is stated to last up to 10 days. Users can program alarms with two different schedule options and can get a warning up to 20 minutes before their sugar drops too low. The G6 promises to block interference from acetaminophen intake.


Eversense promises an accurate sensor no matter your circumstances (sleeping on it or exercising). A water-resistant transmitter sends data from the glucose meter to a smart device every five minutes, but alerts are also available so that you can handle levels that require immediate attention. The compatible mobile app will you to keep track of workouts and meals so you can better see how your daily activities affect your diabetes.

Guardian Connect

If you're the type to want to be proactive rather than reactive with your health, you might want to seriously look into the Guardian Connect system. Calling itself the only system on the market that can "predict" high or low sugar levels, this system promises to give you a warning up to an hour before your the sugar in your blood reaches a level that needs to be seriously addressed. This device works with both ios and android devices.

These are just a few of the many wonderful health benefits that can be provided to people suffering from diabetic symptoms should they choose to employ one of these types of monitoring devices. Of course, make sure to get advice from a medical professional and always follow the orders of your doctor's prescription when using one of these devices.

kaelyn buzzo  Kaelyn is a Certified Personal Trainer and Nutrition Coach (ISSA) with a Bachelor’s degree in Creative Writing (English) and a Minor in Nutrition from the University of South Florida. Read More.