What is Continuous Glucose Monitoring (CGM)

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Continuous glucose monitoring (CGM) is a medical device that measures and displays the continuous glucose levels in a person’s bloodstream. It is a valuable tool for individuals with diabetes, as it allows them to closely monitor their blood sugar levels in real-time and make adjustments to their insulin doses as needed.

CGM can also be useful for people who are at risk of developing diabetes or who want to better understand how their diet and lifestyle affect their glucose levels. In this article, we will provide a detailed overview of CGM, including how it works, its benefits and limitations, and how to use it effectively.

How CGM Works

CGM consists of two main components: a small sensor that is inserted just under the skin and a device that displays the glucose levels in real time. The sensor measures glucose levels in the interstitial fluid, which is the fluid that surrounds the body’s cells. It sends this information to the display device, which can be separate or can be integrated into a smartphone or other device.

There are several different brands of CGM available on the market, and they all work in slightly different ways. Some are used in combination with insulin pumps, while others are used on their own. The sensors typically need to be replaced every one to three days, depending on the brand and type of CGM being used.

Benefits of CGM

CGM has several benefits for people with diabetes, including:

  • Real-time glucose monitoring: With CGM, individuals with diabetes can see their glucose levels in real-time, allowing them to make adjustments to their insulin doses as needed. This can help to prevent both high and low blood sugar levels, which can be dangerous if not properly managed.
  • Improved glucose control: Studies have shown that CGM can improve glucose control in people with diabetes, particularly those with type 1 diabetes. This can lead to better long-term outcomes, such as a reduced risk of complications such as neuropathy, retinopathy, and nephropathy.
  • Increased awareness: CGM can help individuals with diabetes to better understand how their diet, physical activity, and stress levels affect their glucose levels. This can lead to improved self-management and better overall health.
  • Convenience: CGM can be more convenient than traditional glucose monitoring methods, which often require multiple fingerstick glucose readings per day. With CGM, individuals can simply check their glucose levels on the display device or smartphone app, rather than having to perform finger stick tests.

Limitations of CGM

While CGM can be a valuable tool for managing diabetes, it is important to be aware of its limitations. Some of the main limitations of CGM include:

  • Sensor accuracy: CGM sensors are not always completely accurate, and the accuracy can vary depending on several factors such as the location of the sensor, the type of sensor, and the individual’s activity level. This can make it difficult to rely on CGM readings alone for making insulin-dosing decisions.
  • Initial cost: CGM systems can be expensive, particularly for individuals who do not have insurance coverage. This can be a barrier for some people who might otherwise benefit from using CGM.
  • Sensor insertion: The sensor must be inserted just under the skin, which can be uncomfortable for some people. The insertion process also requires proper training to ensure that the sensor is inserted correctly.
  • Maintenance: CGM sensors need to be replaced every one to three days, which can be inconvenient for some people. In addition, the sensors and display devices need to be cleaned and maintained regularly to ensure that they are working

When should I consult a doctor?

When you have any questions regarding how to operate a CGM device properly, contact your provider.  When left untreated for an extended period, extremely low or high blood sugar levels can be harmful.

Seizures, comas, and even death can result in the most serious conditions. You can prevent these consequences by maintaining a normal level of sugar. If you are experiencing any concerns about your symptoms, contact your doctor.

High blood sugar symptoms commonly include: Urination more often, More thirst than normal, Vomiting or nausea, and having trouble thinking clearly.

Who can use a CGM?

If any of the following apply to you, you can use a CGM:

  • Significant lows and highs in your blood sugar levels for no apparent cause.
  • Diabetes during pregnancy, or gestational diabetes.
  • If you use a pump for insulin.
  • Blood sugar levels that are extremely low, known as hypoglycemia, or extremely high, known as hyperglycemia.


It might take some time to learn how to utilize a CGM device. It is not a cure for diabetes or a fast fix. However, it can improve your understanding of the condition. A CGM device allows you to monitor glucose trends more closely. By looking at the larger picture, you can avoid issues or detect them early on, allowing you to better monitor your health. 

The automatic, “always-on” configuration of CGM may provide you with additional flexibility, freedom, and a sense of security. It may also allow you to focus on other things without having to worry about your blood sugar as much.

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