How to Use a Continuous Glucose Monitor (CGM) for Better Blood Sugar Management

18 Sep 2025 By Sandeep R. Pagali, M.D., M.P.H.

How to Use a Continuous Glucose Monitor (CGM) for Better Blood Sugar Management

Managing blood sugar levels effectively is crucial for individuals with diabetes or those looking to optimize their metabolic health. A Continuous Glucose Monitor (CGM) provides a powerful tool for real-time monitoring and analysis of glucose trends. This article delves into how to use a CGM effectively, covering the basics, benefits, practical tips, and troubleshooting advice. By understanding and utilizing the insights from a CGM, you can make informed decisions about diet, exercise, and medication, leading to improved blood sugar control and overall well-being.

What is a Continuous Glucose Monitor (CGM)?

A CGM is a small, wearable device that tracks glucose levels continuously throughout the day and night. Unlike traditional blood glucose meters (BGMs), which require finger pricks for individual measurements, a CGM provides a stream of data at regular intervals, typically every 5 to 15 minutes. This allows for a more comprehensive understanding of how glucose levels fluctuate in response to various factors such as meals, physical activity, stress, and sleep.

Key Components of a CGM:

Sensor: A small, thin wire inserted under the skin (usually in the abdomen or arm) that measures glucose levels in the interstitial fluid.
Transmitter: A device attached to the sensor that wirelessly sends glucose data to a receiver or compatible smartphone app.
Receiver/Smartphone App: Displays real-time glucose readings, trends, and alerts. Many CGMs also offer historical data and reporting features.

Benefits of Using a CGM:

Real-Time Glucose Data: Provides immediate feedback on glucose levels, allowing for timely interventions.
Trend Arrows: Indicates the direction and rate of change of glucose levels (e.g., rising, falling, stable).
Customizable Alerts: Notifies users when glucose levels are too high or too low, enabling proactive management.
Comprehensive Glucose Insights: Helps identify patterns and triggers that affect glucose levels, such as specific foods or activities.
Improved Glycemic Control: Empowers users to make informed decisions about lifestyle and medication adjustments, leading to better HbA1c levels.
Reduced Risk of Hypoglycemia: Alerts can help prevent dangerous low blood sugar episodes, especially during sleep.

Getting Started with a CGM: A Step-by-Step Guide

Embarking on the journey with a CGM requires careful preparation and understanding. This section provides a step-by-step guide on how to get started, from selecting the right device to proper sensor insertion and initial setup.

1. Choosing the Right CGM System

Several CGM systems are available on the market, each with its own features, benefits, and limitations. Consider the following factors when selecting a CGM:

Accuracy and Reliability: Look for systems with proven accuracy in measuring glucose levels.
Ease of Use: Choose a system that is easy to apply, calibrate, and interpret the data.
Comfort: Consider the size and placement of the sensor for optimal comfort.
Connectivity: Ensure the system is compatible with your smartphone or other devices.
Cost: Compare the upfront and ongoing costs of different systems, including sensors and transmitters.
Features: Evaluate the features offered, such as customizable alerts, trend arrows, and reporting capabilities.

Popular CGM Systems:

| CGM System | Key Features | Pros | Cons | |-------------------|----------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------| | Dexcom G7/G6 | Real-time glucose readings, trend arrows, customizable alerts, smartphone integration. | High accuracy, user-friendly interface, integration with insulin pumps. | Requires initial calibration, can be expensive. | | Abbott FreeStyle Libre 3/2 | Factory-calibrated, real-time glucose readings (Libre 3), optional alarms (Libre 2), smartphone app. | No fingerprick calibration required, cost-effective, convenient flash glucose monitoring. | Accuracy may vary slightly compared to Dexcom, limited integration with insulin pumps (Libre 3). | | Medtronic Guardian Connect | Real-time glucose readings, predictive alerts, integration with Medtronic insulin pumps. | Integration with Medtronic pumps, predictive alerts for proactive management. | Requires frequent calibrations, may be less user-friendly than other systems. | | Senseonics Eversense E3 | Implantable sensor with long-term wear (up to 180 days), real-time glucose readings, on-body vibratory alerts. | Longest sensor duration, on-body alerts, no need for frequent sensor changes. | Requires a minor in-office procedure for insertion and removal, more expensive than other systems. |

Consult with your healthcare provider to determine which CGM system is best suited for your individual needs and preferences.

2. Preparing for Sensor Insertion

Before inserting the CGM sensor, gather all the necessary supplies and follow the manufacturer's instructions carefully.

Supplies Needed:

CGM sensor applicator
Alcohol swabs
Adhesive wipes (optional)
Transmitter (if not pre-attached to the sensor)

Preparation Steps:

Choose an Insertion Site: Select a site on the abdomen or back of the upper arm, as recommended by the manufacturer. Avoid areas with scars, moles, or excessive hair.
Clean the Site: Thoroughly clean the insertion site with an alcohol swab and allow it to dry completely.
Apply Adhesive Wipe (Optional): If desired, apply an adhesive wipe to the insertion site to improve sensor adhesion.
Prepare the Sensor Applicator: Follow the manufacturer's instructions to load the sensor into the applicator.

3. Inserting the Sensor

Carefully insert the CGM sensor using the provided applicator.

Insertion Steps:

Remove the Cap: Remove the cap from the sensor applicator.
Position the Applicator: Place the applicator firmly against the cleaned insertion site at a 90-degree angle.
Press the Button: Press the button on the applicator to insert the sensor.
Remove the Applicator: Gently remove the applicator from the insertion site.
Attach the Transmitter: If the transmitter is not pre-attached to the sensor, attach it securely to the sensor.

4. Calibrating the CGM

Some CGM systems, such as Dexcom G6/G7, require calibration with fingerprick blood glucose readings. Calibration helps ensure the accuracy of the CGM readings. Follow the manufacturer's instructions for calibration.

Calibration Steps:

Perform a Fingerprick Blood Glucose Test: Use a blood glucose meter (BGM) to measure your blood glucose level.
Enter the BGM Reading: Enter the BGM reading into the CGM receiver or smartphone app.
Follow Calibration Schedule: Calibrate the CGM according to the manufacturer's recommended schedule, typically once or twice daily.

5. Setting Up Alerts and Notifications

Customize the CGM's alerts and notifications to receive timely warnings about high and low glucose levels. How Insulin Works To Control Blood Sugar In Type 1 And Type 2 Diabetes

Alert Settings:

High Glucose Alert: Set an alert for when glucose levels exceed a target range (e.g., 180 mg/dL).
Low Glucose Alert: Set an alert for when glucose levels fall below a target range (e.g., 70 mg/dL).
Urgent Low Glucose Alert: Set an alert for when glucose levels are dangerously low (e.g., 55 mg/dL).
Rate of Change Alerts: Set alerts for when glucose levels are rising or falling rapidly.

6. Monitoring Glucose Data and Trends

Regularly monitor the CGM's glucose data and trends to gain insights into how your body responds to different factors. Understanding Your Blood Sugar Chart What Normal Blood Sugar Levels Mean

Data Interpretation:

Real-Time Glucose Readings: Check the current glucose level to make immediate decisions about food, exercise, or medication.
Trend Arrows: Use the trend arrows to anticipate future glucose levels and take proactive steps to prevent highs or lows.
Graphs and Charts: Analyze the glucose graphs and charts to identify patterns and trends over time.

Maximizing the Benefits: Practical Tips for Effective CGM Use

To fully leverage the power of a CGM, it's essential to adopt best practices for data interpretation, lifestyle adjustments, and communication with your healthcare team. This section provides practical tips to help you maximize the benefits of your CGM and achieve better blood sugar management. Glycemic Index Vs Glycemic Load A Simple Guide For Better Blood Sugar Control

1. Understanding Glucose Trends and Patterns

A CGM provides a wealth of data, but understanding the patterns and trends is crucial for effective decision-making.

Key Factors Influencing Glucose Levels:

Food: Carbohydrate intake, meal timing, and portion sizes significantly impact glucose levels.
Exercise: Physical activity can lower glucose levels, but the effect varies depending on the type, intensity, and duration of exercise.
Medications: Insulin and other diabetes medications directly affect glucose levels.
Stress: Stress hormones can increase glucose levels.
Sleep: Poor sleep quality can impair glucose metabolism.
Illness: Infections and illnesses can disrupt glucose control.

Analyzing CGM Data:

Identify Mealtime Spikes: Observe how glucose levels rise after meals and identify foods that cause significant spikes.
Track Exercise Effects: Monitor how glucose levels respond to different types of exercise and adjust meal timing or insulin doses accordingly.
Correlate Stress with Glucose Levels: Note any correlation between stressful events and elevated glucose levels.
Evaluate Sleep Impact: Assess how sleep quality affects overnight glucose levels.
Recognize Illness-Related Changes: Be aware of how infections or illnesses impact glucose control and adjust medication doses as needed.

2. Making Lifestyle Adjustments Based on CGM Data

The insights gained from a CGM can empower you to make informed lifestyle adjustments to improve blood sugar control.

Dietary Adjustments:

Reduce Carbohydrate Intake: Lower overall carbohydrate intake, especially from refined carbohydrates and sugary foods.
Choose Low-Glycemic Foods: Opt for foods with a low glycemic index (GI) and glycemic load (GL) to minimize glucose spikes.
Increase Fiber Intake: Consume fiber-rich foods to slow down glucose absorption.
Balance Meals: Include protein and healthy fats in meals to promote stable glucose levels.
Portion Control: Pay attention to portion sizes to prevent overeating.

Exercise Adjustments:

Regular Physical Activity: Engage in regular physical activity to improve insulin sensitivity and lower glucose levels.
Timing of Exercise: Adjust the timing of exercise based on glucose trends to avoid hypoglycemia or hyperglycemia.
Type of Exercise: Experiment with different types of exercise to determine which activities have the most beneficial effect on glucose levels.
Monitor Glucose During Exercise: Check glucose levels before, during, and after exercise to identify patterns and adjust meal or insulin plans accordingly.

Stress Management Techniques:

Practice Relaxation Techniques: Engage in relaxation techniques such as deep breathing, meditation, or yoga to reduce stress levels.
Get Enough Sleep: Prioritize sleep to improve glucose metabolism.
Seek Social Support: Connect with friends, family, or support groups to cope with stress.
Engage in Enjoyable Activities: Participate in hobbies or activities that bring joy and relaxation.

3. Communicating with Your Healthcare Team

Regular communication with your healthcare team is essential for optimizing CGM use and achieving better blood sugar management.

Topics to Discuss with Your Healthcare Provider:

CGM Data Interpretation: Review CGM data and identify patterns and trends.
Medication Adjustments: Discuss any necessary adjustments to insulin or other diabetes medications based on CGM data.
Lifestyle Recommendations: Seek guidance on dietary and exercise adjustments.
Alert Settings: Optimize alert settings for proactive management of high and low glucose levels.
Troubleshooting Issues: Report any issues with the CGM system, such as inaccurate readings or sensor failures.

Sharing CGM Data:

Download CGM Reports: Download CGM reports from the receiver or smartphone app and share them with your healthcare provider.
Use Telehealth Platforms: Utilize telehealth platforms to share CGM data remotely with your healthcare team.
Attend Regular Appointments: Schedule regular appointments with your healthcare provider to review CGM data and discuss treatment plans.

Troubleshooting Common CGM Issues

Despite their advanced technology, CGMs can sometimes experience issues that require troubleshooting. This section addresses common problems and provides practical solutions to help you maintain optimal CGM performance.

1. Inaccurate Glucose Readings

Inaccurate glucose readings can be frustrating and lead to incorrect treatment decisions. Here are potential causes and solutions:

Causes:

Calibration Issues: Improper or infrequent calibration can affect accuracy.
Sensor Placement: Placing the sensor in an area with scar tissue or poor blood flow can lead to inaccurate readings.
Compression Lows: Pressure on the sensor during sleep can cause falsely low readings.
Dehydration: Dehydration can affect glucose levels in the interstitial fluid.
Medication Interference: Certain medications, such as acetaminophen, can interfere with some CGM systems.
Sensor Malfunction: In rare cases, the sensor may be faulty.

Solutions:

Calibrate Regularly: Calibrate the CGM according to the manufacturer's instructions.
Choose Appropriate Insertion Sites: Select insertion sites with good blood flow and avoid areas with scar tissue.
Avoid Compression: Change sleeping positions to avoid pressure on the sensor.
Stay Hydrated: Drink plenty of fluids to maintain adequate hydration.
Check Medication Interactions: Consult with your healthcare provider about potential medication interactions.
Replace the Sensor: If inaccurate readings persist, replace the sensor.

2. Sensor Adhesion Problems

Poor sensor adhesion can lead to premature sensor failure and inaccurate readings.

Causes:

Sweating: Excessive sweating can loosen the adhesive.
Water Exposure: Prolonged exposure to water can weaken the adhesive.
Skin Oils: Natural skin oils can interfere with adhesion.
Improper Application: Incorrect sensor application can compromise adhesion.

Solutions:

Clean the Skin Thoroughly: Clean the insertion site with alcohol and allow it to dry completely before applying the sensor.
Use Adhesive Wipes: Apply adhesive wipes to improve sensor adhesion.
Secure the Sensor: Use overpatches or adhesive tape to secure the sensor.
Avoid Prolonged Water Exposure: Protect the sensor from prolonged exposure to water.
Consider Different Insertion Sites: Try different insertion sites to find an area with better adhesion.

3. Connectivity Issues

Connectivity issues can prevent the CGM from transmitting data to the receiver or smartphone app.

Causes:

Distance: Being too far from the receiver or smartphone can disrupt connectivity.
Interference: Electronic devices or physical barriers can interfere with the signal.
Low Battery: Low battery in the transmitter or receiver can affect connectivity.
Software Glitches: Software glitches can sometimes cause connectivity problems.

Solutions:

Stay Within Range: Ensure the transmitter is within the recommended range of the receiver or smartphone.
Minimize Interference: Move away from electronic devices or physical barriers that may be interfering with the signal.
Check Battery Levels: Ensure the transmitter and receiver have sufficient battery power.
Restart Devices: Try restarting the transmitter, receiver, and smartphone.
Update Software: Ensure the CGM software is up to date.

4. Alert Fatigue

Frequent alerts can lead to alert fatigue, which can diminish the effectiveness of the CGM.

Causes:

Overly Sensitive Alert Settings: Alerts that are set too tightly can trigger frequent notifications.
Poor Glucose Control: Frequent high or low glucose levels can result in constant alerts.
Ignoring Alerts: Ignoring alerts can lead to desensitization.

Solutions:

Adjust Alert Settings: Adjust alert settings to be less sensitive and more tailored to individual needs.
Improve Glucose Control: Focus on improving overall glucose control to reduce the frequency of high and low glucose levels.
Respond to Alerts: Respond promptly to alerts to prevent escalation.
Schedule Breaks: Schedule breaks from CGM alerts to avoid burnout.

5. Sensor Failures

Sensor failures can occur due to various reasons and may require sensor replacement.

Causes:

Sensor Malfunction: In rare cases, the sensor may be faulty.
Trauma: Physical trauma to the sensor can damage it.
Infection: Infections at the insertion site can cause sensor failure.
Expiration: Sensors have a limited lifespan and will eventually expire.

Solutions:

Replace the Sensor: Replace the sensor if it fails or expires.
Avoid Trauma: Protect the sensor from physical trauma.
Monitor for Infection: Monitor the insertion site for signs of infection and seek medical attention if necessary.
Follow Expiration Dates: Adhere to the manufacturer's expiration dates for sensor use.

By understanding these troubleshooting tips, you can address common CGM issues promptly and maintain optimal system performance, ultimately leading to better blood sugar management.

In conclusion, using a CGM is a transformative approach to managing blood sugar levels. By following the guidance provided in this article, from understanding the basics to troubleshooting common issues, you can harness the full potential of this technology. Remember to work closely with your healthcare team to interpret the data, make informed decisions about lifestyle and medication, and achieve your health goals. With consistent effort and the insights from your CGM, you can achieve better blood sugar control and improve your overall quality of life.