What is a continuous glucose monitor for diabetes?

William Lee Dubois

A continuous glucose monitor for diabetes is a monitor that uses a sensor that you put under your skin. There, it can stay anywhere from several days to a week depending on the model. This sensor is parked in your interstitial fluid—the water between your cells. So the sensors don’t technically measure blood glucose at all, they measure body fluid glucose, which is really pretty darn close. The sensor connects to a transmitter that beams data wirelessly to a pager-sized receiver. The monitors display not only the latest “blood sugar” reading, but also a line-graph of a varying number of hours. This gives you data in context and in perspective.

For example, you take a finger stick and you find you are at 110. Is this a good number? Maybe. Probably. But you have no context. The number exists in isolation. Now what if I told you that your BGL is 110 and dropping like a rock? That puts the number in a whole new context.

The Born-Again Diabetic: The handbook to help you get your diabetes in control (again)

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Stacy Wiegman, PharmD
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Most people who have diabetes, whether it's type 1 or type 2, test their blood glucose (blood sugar) level by pricking a finger for a tiny drop of blood, which they put on a test strip that's entered into a glucose monitoring machine. A continuous glucose monitor works differently. A tiny sensor is inserted under your skin. It contains a transmitter that sends information about your blood sugar levels to a wireless monitor, similar to a pager. The sensor is left under your skin for a few days to a week before being replaced.

These devices are more expensive than standard glucose monitors and are not as accurate. But because they provide almost minute-by-minute monitoring of your blood sugar, they may allow for more effective blood sugar control. Talk to your doctor to see if a continuous glucose monitor is a good idea for you.

Continuous glucose monitoring (CGM) is the single greatest advance for people with type 1 diabetes since the discovery of insulin, which was almost a century ago. CGM allows a person with diabetes to get a blood sugar reading every five minutes, 24 hours a day, seven days a week. It has arrows to show which direction your blood sugar is going, and sounds an alert for if your blood sugar is dangerously high or low.

CGM has already improved the lives of thousands of infants, children and adults living with diabetes, as well as their loved ones. There are two CGM devices currently on the market, the Dexcom G5 and Medtronic Enlite. These devices have traditionally been used for people with type 1 diabetes. However, they will soon be used to a much greater extent by people with type 2 diabetes.

Dr. Jack Merendino, MD

We are just at the beginning of some significant advances in glucose monitoring, and one of the most exciting is the development of continuous glucose monitors, or CGMs. There are several CGM systems currently available, including those made by Medtronic MiniMed, DexCom, and Abbott Laboratories. These devices rely on a small, flexible catheter placed into the fat under the skin, similar to the tube through which insulin flows from an insulin pump. Glucose levels in the fluid between the fat cells, called interstitial fluid, are measured, and the results are sent by radio waves to a separate receiver. These measurements are fairly close to blood glucose readings.

Measurements are made every one to five minutes, and the receiver displays the current glucose reading as well as a graph of how the glucose levels are changing. At present, CGM systems are not as accurate as finger-stick blood glucose test results, so some finger-stick testing is still required for validation of the results and is recommended whenever there is a high or low number that would require action on the part of the wearer. The devices have audio and vibrating alarms that can be set for glucose levels above or below a certain number, and one of the most valuable roles for these CGMs is to provide a warning alarm for low-blood-sugar reactions in people who do not have symptoms during hypoglycemia (a condition called hypoglycemic unawareness).

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.