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CGM Foundations
New to CGM or looking for a refresher? You're in the right place.
Build a practical understanding of continuous glucose monitoring (CGM), including how it works, who may benefit, key clinical metrics, and current guidelines.
Glucose levels change constantly
CGM helps capture these changes by measuring glucose in interstitial fluid every few minutes. Unlike a single glucose measurement, CGM provides a dynamic view of glucose showing where glucose is, where it’s heading, and how it changes over time.
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How CGM works
A CGM is a method of tracking glucose using a small wearable sensor. The sensor measures glucose in the interstitial fluid just under the skin's surface, sending the user's current level and the direction it's headed to their phone or display device.1,2
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Why use CGM?
More than 155 million Americans are living with diabetes or prediabetes,3 and fewer than 7% of US adults have optimal cardiometabolic health.4 Continuous glucose patterns offer a window into how nutrition, physical activity, sleep, stress, medications, and daily routines impact diabetes and metabolic health.
Learn more about the benefits of CGM with each of these resources5,6,7
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Who may benefit from CGM?
Clinical guidelines
Clinical practice guidelines provide recommendations regarding appropriate use of CGM across various patient populations. Although recommendations continue to evolve, major professional organizations increasingly recognize CGM as an important tool in diabetes management.
ADA Standards of Care
Explore guideline recommendations related to CGM use and diabetes technology from the American Diabetes Association (ADA).
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Understanding CGM data
CGM generates a large amount of glucose information. To simplify interpretation, clinicians often focus on a set of core metrics that provide a high-level view of glucose management.
Understanding these foundational measures can help clinicians become more comfortable reviewing CGM reports and discussing glucose patterns with patients.7
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Time in Range (TIR)
The percentage of time glucose values remain within a target range.
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Time Above Range (TAR)
The percentage of time glucose values exceed the target range.
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Time Below Range (TBR)
The percentage of time glucose values fall below the target range.
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Glucose Management Indicator (GMI)
An estimate based on average glucose levels.
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Glycemic Variability
A measure of how much glucose levels fluctuate throughout the day.
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CGM in clinical practice
References
1 Dexcom G7 15 Day User Guide. 2 Stelo User Guide. 3 Centers for Disease Control and Prevention. National Diabetes Statistics Report. Atlanta, GA: U.S. Department of Health and Human Services; 2026. Accessed August 6, 2026. https://www.cdc.gov/diabetes/php/data-research/index.html. 4 American Diabetes Association. Standards of Care in Diabetes—2026. 4. 5 Reed J, et al. Diabetes Obes Metab. 2024;26(7):2881-2889. 6. Clark TL, et al. Diabetes Technol Ther. 2024;26(10):700-708. 7. Battelino T, et al. Diabetes Care. 2019;42(8):1593–1603.