Continuous Glucose Monitors (CGMs) provide real-time insights into glucose levels, moving beyond traditional fingerstick tests. Many users, or those considering a CGM, often inquire about the “needle” component and the insertion process. Understanding how these systems work can alleviate concerns and clarify what to expect.
The CGM Sensor Insertion Process
A CGM sensor is applied using an applicator, a device designed for quick and straightforward insertion. This applicator contains a temporary needle, or introducer, that guides the sensor into the interstitial fluid, the fluid surrounding the body’s cells where glucose is measured. Once positioned, the temporary needle retracts and remains within the applicator, meaning it does not stay in the body. What remains under the skin is a small, flexible filament, the actual sensor component. This filament is pliable and comfortable, continuously measuring glucose for days to weeks, depending on the model.
Applying the sensor involves cleaning the chosen site with an alcohol wipe and allowing it to dry. The applicator is placed firmly against the skin, a button is pressed, and after a click, the applicator is removed. This leaves the sensor securely attached with an adhesive patch.
What Determines Sensor Size
The temporary insertion needle is very fine, similar to a 23-gauge needle (approximately 0.64 mm thick). This needle minimizes discomfort during the brief insertion.
Its length varies but is generally a few millimeters, designed to reach subcutaneous tissue. For instance, some microneedle array sensors use needles as short as 1 mm, while other systems might have introducer needles around 5-13 mm long. The goal is to ensure proper sensor placement without damaging blood vessels.
The sensor itself is a flexible filament, a thin wire or cannula, that stays under the skin. Its length can vary, with some around 4 mm long and 0.3 mm wide, and others around 7 mm long and 0.7 mm wide. This filament is made from flexible materials like titanium and is coated with enzymes to detect glucose.
Minimizing Discomfort During Insertion
Minimizing discomfort during CGM sensor insertion involves several steps. Selecting an appropriate site is key, with common areas including the back of the upper arm, abdomen, or upper buttocks, depending on device guidelines. Choose a site free from scars, tattoos, or irritated skin, and avoid bony areas.
Before applying, clean the area with an alcohol wipe and allow it to dry. Moisture, lotions, or oils can interfere with the adhesive and cause irritation. Applying the sensor quickly and confidently can also contribute to a more comfortable experience.
Relaxing muscles around the insertion site can help. While a momentary sensation of pressure or a slight prick may occur, the flexible sensor filament typically causes no ongoing pain. Rotating insertion sites with each new sensor application helps prevent skin irritation and allows previous sites to heal.