Continuous Glucose Monitoring


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Editors
Eden Miller, MD
Davida Kruger, MSN, APN-BC
Dennis Harris, PhD
Kurt Midyett, MD

Additional Resources
Mayo Clinic
NIDDK (NIH)

What is continuous glucose monitoring?

Continuous glucose monitoring, also called CGM, is a way for people with diabetes to monitor glucose levels. CGM measures glucose levels in the fluid between body cells every few minutes throughout the day and night.

The most common way to check blood glucose is to prick a finger to get a drop of blood (a fingerstick), then test the blood with a blood glucose meter. This is test is done between 1-6 times per day and can be difficult for most people. Using a CGM allows you to check blood glucose automatically 280 or more times each day; even while you are asleep. This frequent monitoring can lead to better outcomes when managing diabetes. These results are used to help make decisions about insulin, food, exercises and help healthcare providers understand how medicines are working.

CGMs use a tiny sensor to test the fluid between the body cells. This sensor checks the level of glucose every few minutes. The information is then sent wirelessly to a reader that shows the glucose levels. Some CGMs can even send this information right to your phone so that you can share it with a family member or Health Care Specialists. There are several CGM systems available. Each system is a little different in the how glucose levels are checked and how glucose levels are shown.

How does CGM work?

Most CGM systems consists of three main parts:

  1. A small, disposable sensor is inserted under the skin to measure glucose in the body fluid. The sensor is replaced every 3–7 days, depending on the model.
  2. The transmitter is a small device that attaches to the sensor and is placed on the skin. It uses radio waves to send information about glucose levels to a wireless monitor, also called a receiver.
  3. The monitor, a device the size of a cell phone, shows information about glucose levels on a screen. Users wear the monitor on a belt or keep it in a pocket. The monitor includes the alarm that warns of out-of-target glucose levels. In some models, information can be displayed directly on an insulin pump.

CGM systems provide several kinds of reports about glucose levels. For example, one report graphs average glucose levels for several hours or a whole day and night. CGM systems also allow users to note when they eat meals or take medicines, which can help you understand their glucose trends.

Who can use a CGM?

Changes in glucose levels can happen very quickly or unexpectedly. If you have type 1 diabetes or type 2 diabetes and need to take insulin, a CGM system may be right for you. Depending on the CGM, children as young as 2 years old can even use CGMs. Studies have shown that CGMs can help people living with diabetes keep blood glucose levels on target without an increased risk of severe hypoglycemia. Staying on target can mean fewer health problems, day-to-day and in the long run.

Some people may decide that CGM is not for them.They find it hard to get used to having a sensor under the skin and dealing with alarms. Some may be overwhelmed by the amount of information CGM provides or may not be comfortable with technology.

There are also different ways that a CGM can be used and how often it is used can vary for each person.

  • CGMs can be used if you are taking insulin injections or using an insulin pump
  • CGMs can be used continuously or for brief periods of time

Talk with your healthcare team about what is best for you.

Benefits of using a CGM?

In recent years, CGMs have become just as accurate as blood glucose meters. Allowing for insulin dosing and decisions to be made directly from the CGM.

  • CGMs show the changes glucose levels around the clock, this can help in the decisions you make about insulin, food, and exercise.
  • They show how fast glucose levels are changing, to make help decisions about adjustments needed to help keep glucose levels in a safe range.
  • Provide useful reports on your glucose trends to help make decisions about care.
  • Send alarms or alerts when glucose levels are too high or too low and can also give a prediction if the glucose level might be high of low in the near future.
  • Offer easy sharing with healthcare teams and/or family members.

Blood glucose meters and CGMs both show your current glucose level. But CGMs can also record the past levels reports the present and predicts the future glucose levels.

Trend arrows are a big advantage of using a CGM. Trend arrows are typically small arrows that helps you know where your glucose level is heading. For example, if you see trend arrows pointing down, you can expect your glucose level is going to drop. This can help you plan ahead and catch high or low glucose levels before they become dangerous.

Trend arrows can also be used to adjust the amount of insulin you take with meals. The exact amount of insulin that you add or subtract depends on the person taking the insulin and on the type of CGM system you are using because not all trend arrows are the same. It is important to talk to your healthcare team to help you understand what the trend arrows mean before using trend arrows to adjust your insulin. Each commonly used continuous glucose monitor has special features like- who can use them, how the sensor is inserted, how data is collected shown and shared.

Talk with your healthcare provider about what is best for you.

Learn More about Commonly Used Continuous Glucose Monitors

Questions to ask your healthcare team:

  • Does CGM fit into my diabetes management plan?
  • What adjustments would I need to make in my diabetes management plan to use a CGM?
  • What are the advantages and disadvantages of CGM for me?
  • Can I try out a CGM system before buying one?
  • How often should I review the data from my reader with you?
  • How often should I scan?
  • Is CGM covered by my insurance plan?
  • Should I see a diabetes specialist for my care?

Edited: November 2018