A Continuous Glucose Monitor (CGM) is a compact system designed to track glucose levels throughout the day and night without requiring constant fingerstick checks. The technology uses a tiny sensor wire inserted just beneath the skin to measure glucose in the interstitial fluid, which is the fluid surrounding the body’s cells. These readings are then relayed wirelessly to a display device, like a smartphone or dedicated receiver, providing real-time data and trend arrows. Understanding the device’s duration is important, as a CGM system is composed of multiple parts, each with its own distinct replacement schedule.
Standard Lifespan of the Disposable Sensor
The disposable sensor contains an electrode coated with an enzyme that reacts with glucose. Manufacturers design these sensors with a specific, limited lifespan to ensure accuracy and prevent material degradation. The standard wear time for these wearable sensors typically ranges from 7 to 14 days, though duration varies by brand and model.
Popular models vary in duration. The FreeStyle Libre system is authorized for a 14-day wear time before requiring replacement. Devices like the Dexcom G6 and G7 sensors function optimally for 10 days.
The limit on wear time is dictated by the stability of the sensor’s electrochemical components. The enzyme used to measure glucose naturally degrades over time, reducing the sensor’s ability to provide accurate readings beyond the approved period. Additionally, the physical components, including the tiny wire and the adhesive patch, are not designed for indefinite use on the skin.
Factors That Can Shorten Sensor Wear Time
Various factors can force a user to remove and replace a sensor prematurely, despite its pre-determined lifespan. Physical trauma or impact to the application site is a common cause of early removal. The sensor can be easily dislodged by bumping into objects or if it is poorly placed where clothing constantly rubs against it.
Adhesive failure is a frequent issue, often exacerbated by moisture, heat, or skin oils. Excessive sweating or prolonged water exposure can weaken the adhesive bond, causing the patch to lift or the sensor to fall off completely. Users often employ skin barrier wipes before application and use over-patches to reinforce the adhesive.
Technical malfunctions can also necessitate early replacement, even if the sensor is physically intact. These issues include signal errors, problems during the initial warm-up phase, or a complete device malfunction that prevents data transmission. Accuracy drops may also indicate the sensor is no longer reliable, prompting the user to end the session early.
Lifecycles of the Non-Disposable CGM Components
The CGM system includes components with a much longer lifespan that are reused across multiple sensor sessions. The transmitter is the small piece that snaps onto the sensor, collecting glucose data and sending it wirelessly to the display device. Because the transmitter contains an internal battery and Bluetooth technology, it must be replaced periodically.
The Transmitter
The lifespan of a transmitter varies significantly by manufacturer, generally ranging from three months to a full year. The Dexcom G6 transmitter is designed to last approximately 90 days, after which the battery depletes and the unit must be replaced. Other systems, such as some Medtronic Guardian transmitters, are engineered with a battery life that can extend up to 12 months.
The Receiver
The receiver or reader is the handheld device that displays the glucose information if the user chooses not to use a smartphone application. Unlike the sensor and the transmitter, the receiver is a durable piece of medical equipment without a set replacement schedule. These devices are expected to last for several years, similar to a mobile phone, and are only replaced if damaged or when the user upgrades to a newer system model.