CGMs provide real-time data on glucose fluctuations, transforming diabetes management. Magnetic Resonance Imaging (MRI) is a powerful diagnostic tool that uses strong magnetic fields and radio waves to create detailed images of organs and tissues. For individuals relying on a CGM, the MRI environment poses a significant risk to the wearable device and the patient. This conflict forces users to balance the necessity of diagnostic imaging with the continuity of their glucose monitoring.
Official Guidance on CGM Use During MRI
Whether a CGM can be worn during an MRI depends on the specific device model, but official guidance for most mandates removal. Manufacturers like Dexcom and those associated with insulin pump systems (e.g., Omnipod) explicitly state that all components—sensor, transmitter, and receiver—must be removed before entering the MRI suite. This instruction is based on testing designed to prevent device failure and patient injury.
Recent developments have introduced exceptions. Certain Continuous Glucose Monitoring systems, such as the FreeStyle Libre 2 and Libre 3 sensors, have received clearance from the U.S. Food and Drug Administration (FDA) to be worn during MRI procedures under specific conditions. This clearance is not universal; users must confirm the exact model and follow limitations regarding magnetic field strength and scanning duration. Even if the sensor remains in place, the receiver, smartphone, or reader must be kept outside the exam room.
Understanding the Physical Hazards
The primary safety concern with wearing most CGMs during an MRI procedure is the risk of severe tissue heating. The strong radiofrequency energy pulses emitted by the MRI machine induce electrical currents within the small metallic components, such as the sensor’s delicate wire filament. This causes rapid heating, which can lead to localized, deep skin burns at the insertion site that are difficult to detect during the scan.
Beyond thermal risks, the powerful static and gradient magnetic fields can cause immediate device malfunction. The electronic components and memory within the transmitter are susceptible to corruption or destruction from the magnetic field, potentially rendering the device useless. Furthermore, the presence of metallic materials introduces significant image artifacts, known as susceptibility artifacts. These artifacts appear as distorted black voids or signal loss, severely obscuring the anatomy being imaged and rendering the diagnostic procedure ineffective.
Pre-MRI Device Removal Protocol
For any Continuous Glucose Monitoring system not explicitly cleared to remain in place, a specific removal protocol must be followed to ensure patient safety. The first step involves coordinating the timing of the MRI appointment with the end of the sensor’s wear cycle whenever possible, minimizing the loss of a functioning device. Users must inform the MRI technologist or radiologist about the device’s presence, who will confirm the necessity of its removal before the patient enters the procedure room.
The physical removal involves carefully peeling the adhesive patch and withdrawing the sensor and transmitter according to manufacturer instructions. The removed sensor must be discarded, as its accuracy cannot be guaranteed after potential exposure to the MRI environment. It is highly recommended to bring a traditional blood glucose meter, test strips, and an insulin pen or syringe to the appointment, ensuring immediate access to glucose monitoring and treatment supplies. A new sensor should only be applied immediately following the scan to begin the necessary warm-up period as soon as possible.
Managing Glucose Monitoring Gaps
Removing the CGM for an MRI creates a temporary, significant gap in continuous glucose data. To manage this period safely, individuals must temporarily revert to traditional fingerstick blood glucose checks (capillary testing). Manual testing provides the necessary real-time data points for immediate treatment decisions, such as insulin dosing.
Increased vigilance for both hypoglycemia and hyperglycemia is necessary before, during, and immediately after the procedure. The last glucose reading before entering the MRI and the first reading afterward should both be fingersticks to establish a baseline before relying on a new sensor. It is prudent to notify the diabetes care team about the planned monitoring interruption for guidance tailored to the patient’s insulin regimen and the gap duration. Even for systems that remain in place, readings may be inaccurate for up to an hour after the scan, requiring temporary reliance on a glucometer for treatment decisions.