A Continuous Glucose Monitor (CGM) is a small, wearable device that tracks glucose levels non-invasively, providing a continuous picture of blood sugar trends throughout the day and night. The device consists of a tiny sensor inserted just under the skin, which measures glucose in the interstitial fluid, and a transmitter that sends this data to a receiver or smartphone app. For many users, this technology is invaluable for managing diabetes without constant finger pricks. The core question for anyone with an active lifestyle, however, is whether this electronic device can withstand exposure to water, especially when swimming.
Understanding CGM Water Resistance
Most modern CGMs are designed to be water-resistant, a specification defined by Ingress Protection (IP) ratings, not a guarantee of being completely waterproof. These ratings indicate how well a device is sealed against solids and liquids. For instance, an IPX7 rating means the sensor can be submerged in up to one meter of water for 30 minutes, while an IPX8 rating allows for submersion beyond one meter or for a longer duration, depending on the manufacturer’s specific testing.
These standards are typically tested in pure, static water under controlled conditions. High-pressure or high-velocity water, such as from diving, high-impact water sports, or a powerful showerhead stream, can compromise the device’s seal, even if it is rated for typical swimming.
The adhesive bond is often the weakest point. While the sensor itself may be water-resistant, chlorine, saltwater, or prolonged exposure can weaken the patch. Extreme heat or cold can also affect the device’s performance. Therefore, recreational swimming is generally safe within the manufacturer’s specified depth and time limits, but the primary risk is sensor detachment rather than internal electronic failure.
Pre-Swim Preparation and Protection
The most effective strategy for swimming with a CGM is securing the sensor’s adhesion before entering the water. A new sensor should be applied several hours, ideally 12 hours, before swimming to allow the adhesive to fully cure and form a stronger bond with the skin. The application site must be thoroughly cleaned with soap and water, wiped with an alcohol swab, and allowed to air dry completely to remove all residual oils and lotions.
Many users rely on auxiliary protection methods, such as applying external adhesive patches, tapes, or protective covers specifically designed for CGMs. These overlays, often made of stretch-fabric, extend beyond the sensor’s original adhesive footprint to distribute shear forces and prevent the edges from lifting. Choosing an appropriate sensor site, such as the back of the upper arm, can also minimize the risk of the device being snagged or rubbed off during extended water activity.
Troubleshooting After Water Exposure
Even with careful preparation, water exposure can lead to issues requiring immediate troubleshooting. The most common sign of compromised sensor integrity is adhesive peeling or lifting, which allows moisture to reach the insertion site. If the transmitter appears loose or water bubbles are visible under the patch, the sensor seal is likely broken, and its accuracy may drop.
A temporary period of false or erratic glucose readings may occur immediately following swimming due to temperature changes or dehydration. Water activity can affect blood flow and interstitial fluid, causing a time lag or inaccuracy in the glucose reading. It is advisable to allow the sensor site to dry and the body’s temperature to stabilize before fully trusting the displayed glucose value. If readings do not match physical symptoms, a finger-stick blood glucose check should be performed. If the sensor completely fails or the adhesive is significantly compromised, it must be safely removed and replaced following the manufacturer’s instructions.