Jan 3, 2024

CGM and Exercise

How Continuous Glucose Monitoring (CGM) can help you unlock your exercise potential and improve diabetes management

Exercise is super important for managing type 1 diabetes and living a healthy life. However, exercise has a big impact on glucose levels and is still challenging to manage for many people. The way your glucose levels change depends on a bunch of factors including how intense and how long the exercise session is. It's totally normal to be worried about the risk of low blood glucose when you're exercising.

There have been leaps and bounds in the advancement of technologies for managing diabetes in recent years. This is mainly because a lot of research has been dedicated to improving all aspects of diabetes patient care, including improving time spent in target range, lowering the risk of complications, addressing the psychological challenges associated with living with the condition, and making the decision-making process around glucose management easier.

Continuous glucose monitoring, or CGM, has made managing glucose levels much easier compared to relying on fingerstick tests alone. With CGM, you can track your glycemic responses to different types of exercise almost in real-time, and those trend arrows give you a heads up on where your glucose levels are headed. Plus, you don't have to keep stopping your workout to do a glucose measurement because you can just check your values on your phone, smartwatch, or even your cycling computer. And on top of that, looking at the data after your exercise sessions can help you to fine-tune your insulin and nutrition strategies as an athlete.

However, understanding CGM, both for the person living with type 1 diabetes and their healthcare professionals, can be quite a challenge. Many people may have difficulty interpreting the provided information to fully utilize the technology's potential around exercise (i.e. before, during, and after your workout).

What is CGM?

A Continuous Glucose Monitor (CGM) is a body worn small device that measures and keeps track of your glucose levels in real-time 24/7. It's designed to help individuals with diabetes monitor their glucose levels more comprehensively compared to traditional fingerstick tests, which only provide point-in-time readings.

The CGM is made up of a number of components:

1. Sensor: The CGM system consists of a tiny sensor, which is a thin filament that is usually inserted under the skin on the belly or arm. After insertion, the sensor sits in the space just below the skin and is able to continuously measures glucose levels in the fluid around your cells (this is called the interstitial fluid).

2. Transmitter: The sensor is connected to a transmitter that wirelessly sends the glucose readings to a receiver or a smartphone app. The sensor is constantly analysing circulating glucose levels and send the results to a smartphone or watch via Bluetooth connection.

3. Receiver/App: The receiver or smartphone app displays the glucose readings in real-time, providing a graph showing current levels and trends over time. Some systems have customizable alerts for high or low glucose levels.

4. Trend Analysis: Software then displays the value and helps with the interpretation of the results. CGM devices not only display current glucose levels but also show trends, indicating whether blood sugar is rising, falling, or stable. This helps individuals anticipate potential highs or lows.

What are the advantages of using continuous glucose monitoring (CGM) during and after exercise?

CGM has become an invaluable tool for people with diabetes, providing a more complete picture of their glucose levels, improving diabetes management, and empowering users to make informed decisions about their health in real-time.

  • Real-Time Monitoring: Continuous readings throughout the day and night, giving a comprehensive view of glucose levels.

  • Alerts and Alarms: Customizable alerts let you know when your glucose levels are too high or too low, helping you take quick action to prevent extreme highs or lows.

  • Trend Analysis: CGM gives you insights into how your glucose levels are changing, so you can make informed decisions about how much insulin to take, what to eat, and how to plan your exercise routines.

  • Reduced Fingersticks: While CGM doesn't totally replace fingerstick tests, it can really cut down on how often you need to do them for glucose monitoring.

What to consider when using a CGM

When using a CGM, there are several key metrics that can be useful to help track and manage your glucose levels effectively:

  1. Glucose Trends: Continuous monitoring allows you to keep an eye on the direction and speed of changes in your glucose levels. Knowing these trends is super important for predicting possible highs or lows.

  2. Time in Range (TIR): This metric measures the percentage of time your glucose levels stay within a target range (usually set between specific low and high thresholds). It's a valuable indicator of how well you're managing your blood sugar. Check our article on TIR for a more in-depth understanding of this key metric!

  3. Time Below Range (TBR) or Hypoglycemia: This metric tracks the amount of time your glucose levels are below the lower threshold, indicating potential hypoglycemic events. Managing TBR is crucial to prevent dangerous low blood glucose episodes.

  4. Time Above Range (TAR) or Hyperglycemia: Conversely, TAR measures the time your glucose levels exceed the upper threshold, signaling hyperglycemia.

  5. Glycemic Variability: This metric evaluates the fluctuations in glucose levels over a specific period. Lower variability indicates more stable blood sugar levels.

  6. Glucose Patterns During Specific Activities: Focus on observing how your glucose levels respond to meals, exercise, stress, and sleep. Understanding these patterns helps in adjusting insulin, food intake, or activity levels accordingly.

  7. Rate of Change (ROC): Monitoring the rate at which your glucose levels are rising or falling can be critical to predict and prevent rapid changes that may lead to highs or lows.

  8. Post-Meal Spikes: Observing the peak levels after meals can help optimize mealtime insulin doses or dietary choices to manage post-meal spikes effectively.

These metrics, when analyzed together, provide a comprehensive understanding of your glucose management. They offer insights into patterns, trends, and potential risks, enabling you to make informed decisions about medications, diet, exercise, and overall diabetes management strategies. It's a good idea to regularly check out these metrics and patterns so you can make changes to your diabetes plan and stay healthy.

How can CGM help manage your glucose levels around exercise?

Exercise is a cornerstone of well-being, providing not only physical benefits but also a sense of empowerment, community, and vitality. However, for people living with type 1 diabetes, glucose management around exercise can be really challenging. If you are planning to start your exercise journey, check out our article.

Continuous Glucose Monitoring (CGM) has become a valuable tool for individuals with diabetes, especially during exercise, as it provides real-time insights into glucose levels. With CGM data, you can make informed decisions about adjusting insulin doses or carbohydrate intake before, during, or after exercise. This helps in preventing hypoglycemia (low blood glucose) or hyperglycemia (high blood glucose) episodes triggered by physical activity.

Different types and intensities of exercise can affect blood glucose levels differently. CGM data assists in understanding these variations, allowing individuals to tailor their management strategies accordingly.

CGM can also be beneficial for post-exercise monitoring, as they help track how the body continues to respond to physical activity even after the workout has ended. This is important for preventing delayed hypoglycemia, a common occurrence after intense or prolonged exercise.

Using CGM data during exercise can help improve overall diabetes management. It offers valuable insights into how different factors, such as exercise, affect blood glucose levels.

Extra considerations for using CGM during exercise

There are certain situations when you’re exercising that may require special considerations to use of CGM safely and effectively. This is especially true in situations where blood glucose measurements are inconvenient or cannot be performed such as while swimming or skiing. Below are a few examples where using CGM or checking glucose levels can be more tricky.

Contact sports such as boxing, martial arts, rugby

When competing in contacts sports such as boxing, mixed martial arts, rugby the glucose sensor should be placed at a site with the lowest risk of being hit. To reduce the risk of losing the glucose sensor during contact sports, adhesive tape should be used. If you’re regularly competing in contact sports, implantable sensors might be worth considering.


For swimming, several manufacturers produce small waterproof bags that can be used for CGM. This may be of particular interest if swimming sessions are performed in an open-water setting. If you are doing prolonged swimming session, consider carrying carbohydrates. If swimming is performed in a swimming pool then the reader/scanner and any carbohydrates can be placed by the side of the pool. If you’re a regular swimmer consider using adhesive tape to ensure that the sensor is not getting lost while swimming.

Skiing, snowboarding and other sports undertaken at high altitude

At high altitude, CGMs have shown to be able to measure glucose reliably. Be aware that glucose and insulin requirements may change when exercising at altitude compared to at sea level, therefore extra attention to CGM may be required. Glucose should be measured as often as possible and CGM is a useful tool to assist this. Since high altitude is associated with low temperatures the CGM sensor should be worn close to the body so that it doesn’t get too cold.

Final word on CGM and Exercise

Using a CGM during exercise provides valuable benefits to individuals with diabetes. It offers real-time information, predictive trends, and actionable insights, empowering you to make informed decisions and maintain safe levels during and after physical activity. With the help of CGM data, you can learn and make adjustments to their exercise routines, insulin dosages, or carbohydrate intake patterns, leading to better glucose management during physical activity.

Experience the benefits of comprehensive diabetes management with Enhance-d. Sign up for a free trial with no commitment or credit card required, and subscribe to the newsletter for updates, resources, offers, and early access to Enhance-d related content.

💡 Enhance-d: A Digital Platform for Comprehensive Diabetes Management Enhance-d is a digital diabetes management platform that simplifies decision-making by integrating, analyzing, and presenting all diabetes-related data in a user-friendly manner. The platform brings together data from continuous glucose monitoring (CGM), insulin, exercise, nutrition, sleep, and menstrual cycle tracking, empowering individuals with diabetes to manage their health seamlessly.

With a focus on collaboration, Enhance-d enables users to share information with healthcare professionals for advanced diabetes care. By fostering this partnership, individuals with diabetes can receive expert guidance and support in managing their condition.

Enhance-d is compatible with popular CGM devices and fitness trackers, such as FreeStyle Libre, Dexcom, Garmin, Google Fit, and Fitbit. This compatibility ensures that users can easily integrate their existing devices with the platform, streamlining data collection and analysis.

Visualization tools like the Ambulatory Glucose Profile (AGP) and Exercise View feature further enhance the user experience by providing clear and concise visual representations of diabetes data. These tools empower individuals to better understand and manage their condition, allowing them to take control of their health and maintain an active and healthy lifestyle.

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