CGM Glossary

A blood test measuring average blood glucose levels over the past 2-3 months. It reflects the percentage of hemoglobin coated with sugar and is used to diagnose diabetes and monitor long-term glucose control.

The degree to which a CGM reading matches the actual blood glucose level. CGM accuracy is typically measured using MARD (Mean Absolute Relative Difference).

The medical-grade tape or patch that attaches the CGM sensor to the skin. Some users may experience skin sensitivity or allergic reactions to certain adhesives.

A system that combines a CGM with an insulin pump and algorithm to automatically adjust insulin delivery based on glucose readings. Also known as a closed-loop or artificial pancreas system.

The mathematical formula used by CGMs to convert raw sensor signals into glucose readings, and by AID systems to calculate insulin doses.

A notification from the CGM warning the user of high glucose, low glucose, or rapid glucose changes. Alerts can be customized based on user preferences.

The accumulation of proteins and cells on the sensor surface over time, which can affect sensor accuracy and lifespan.

The concentration of glucose (sugar) in the blood, typically measured in mg/dL (US) or mmol/L (international). CGMs estimate this by measuring interstitial glucose.

Wireless technology used by CGMs to transmit glucose data from the sensor/transmitter to a receiver, smartphone, or insulin pump.

The process of adjusting CGM readings using fingerstick blood glucose measurements. Some modern CGMs are factory-calibrated and don't require user calibration.

A device that continuously measures glucose levels in interstitial fluid through a small sensor inserted under the skin, providing real-time glucose data.

An automated system where CGM data is used to automatically control insulin delivery without user intervention. See also: AID, Artificial Pancreas.

A falsely low glucose reading caused by pressure on the sensor, often during sleep when lying on the sensor site.

A leading CGM manufacturer known for the G6, G7, and Stelo product lines. Dexcom CGMs are known for accuracy and integration with insulin pumps.

A category of medical devices including CGMs that are covered by insurance. CGMs may be covered under DME or pharmacy benefits depending on the payer.

A protein used in CGM sensors (typically glucose oxidase or glucose dehydrogenase) that reacts with glucose to generate an electrical signal.

A calibration method where sensors are calibrated during manufacturing, eliminating the need for fingerstick calibrations by the user.

The U.S. Food and Drug Administration, responsible for regulating and approving CGM devices for sale in the United States.

A blood glucose measurement taken by pricking the finger and applying blood to a test strip. Used for CGM calibration or verification.

Abbott's CGM product line including the Libre 2, Libre 3, and Libre 3 Plus. Known for its flash glucose monitoring and affordable pricing.

A simple sugar that is the body's primary source of energy. Blood glucose levels are what CGMs measure and help manage.

An enzyme commonly used in CGM sensors that catalyzes the oxidation of glucose, producing a measurable electrical signal.

An estimate of A1C based on CGM data. Previously called eA1C (estimated A1C). Useful for tracking glucose control between lab tests.

High blood glucose, typically defined as above 180 mg/dL (10 mmol/L). CGMs can alert users when glucose is rising or has exceeded a threshold.

Low blood glucose, typically defined as below 70 mg/dL (3.9 mmol/L). CGMs can provide early warning alerts to help prevent dangerous lows.

An FDA classification for CGMs that meet specific accuracy and reliability standards, allowing integration with automated insulin delivery systems.

The process of placing the CGM sensor under the skin, typically done with an automatic inserter device.

The fluid between cells where CGM sensors measure glucose. There is typically a 5-15 minute lag between interstitial and blood glucose levels.

The delay between changes in blood glucose and the CGM reading, caused by the time it takes glucose to move from blood to interstitial fluid.

See Freestyle Libre. Abbott's line of continuous glucose monitoring systems.

Lumpy fatty tissue that can develop at insulin injection sites, which can affect CGM sensor accuracy if sensors are placed in these areas.

The standard measure of CGM accuracy, representing the average difference between CGM readings and reference blood glucose values. Lower MARD indicates better accuracy.

The U.S. federal health insurance program for people 65+ and those with disabilities. Medicare covers CGMs for qualifying beneficiaries under specific criteria.

A medical device company that manufactures CGMs integrated with their insulin pump systems, including the Guardian Sensor line.

CGMs that can be purchased without a prescription, expanding access to glucose monitoring for people without diabetes or prescriptions.

An alert that warns of an upcoming high or low glucose event before it happens, based on the current glucose trend.

The glucose values that a user aims to stay within, often called 'time in range' (TIR). The standard target range is typically 70-180 mg/dL.

A CGM that continuously displays glucose data without requiring the user to scan the sensor, as opposed to intermittently-scanned CGM.

A dedicated handheld device that displays CGM data. Many users now use smartphone apps instead of dedicated receivers.

The small, flexible filament inserted under the skin that measures glucose in interstitial fluid. Sensors typically last 7-15 days depending on the system.

The body location where the CGM sensor is placed. Common sites include the abdomen, arm, and upper buttocks.

Random variations in CGM readings that don't reflect actual glucose changes, which algorithms filter out to provide smoother data.

Irritation or allergic reactions that some users experience from CGM adhesives or sensor materials.

Dexcom's OTC CGM designed for people without diabetes who want to track their glucose for wellness purposes.

The percentage of time glucose stays within a target range (typically 70-180 mg/dL). A key metric for assessing glucose control.

The reusable component that attaches to the sensor and wirelessly sends glucose data to a receiver or smartphone.

A visual indicator on the CGM display showing the direction and rate of glucose change (rising, falling, or stable).

The time after sensor insertion before the CGM begins displaying readings, typically 30 minutes to 2 hours depending on the system.