| Dexcom G7 water rating | IPX8 β 2.4 m / 24 hrs |
| Libre 3 water rating | IPX8 β 1 m / 30 min |
| Medtronic Guardian 4 | IPX8 β 2.4 m / 30 min |
| Recommended prep time | 60 sec alcohol dry before insertion |
| Safe distance from navel | Minimum 5 cm for abdominal placement |
Key Takeaways
- Most modern CGMs are water-resistant to 2.4β3 metres for up to 30 minutes (IPX7/IPX8 rated)
- Proper adhesive overlays can extend sensor life significantly in chlorinated or saltwater
- Upper arm and abdomen remain the most reliable placement sites for swimmers
- Rinse sensors with fresh water immediately after swimming to reduce corrosion
- Receivers and phone apps may not share the same water resistance rating as the sensor itself
Water Resistance Ratings Explained
CGM sensors carry IP (Ingress Protection) ratings that define safe water exposure. IPX7 means the device withstands immersion up to 1 metre for 30 minutes; IPX8 extends this to manufacturer-specified depths, typically 2.4 m for 30 minutes. Chlorine, salt, and pressure from diving can degrade adhesives and seals faster than these lab conditions suggest.
| CGM Device | Water Rating | Max Depth | Duration |
|---|---|---|---|
| Dexcom G7 | IPX8 | 2.4 m | 24 hrs |
| Freestyle Libre 3 | IPX8 | 1 m | 30 min |
| Medtronic Guardian 4 | IPX8 | 2.4 m | 30 min |
Best Placement Sites for Swimmers
Upper Arm (Posterior)
The back of the upper arm offers a relatively flat surface with less friction against pool walls. It is the factory-approved site for Libre 3 and increasingly used off-label for Dexcom G7. Avoid placing it on the inner arm where goggles or watch straps may snag the sensor.
Abdomen
The abdomen (at least 5 cm from the navel) is approved for most CGM systems. It stays largely undisturbed during freestyle and backstroke, but breaststroke kick can increase flexion and loosen edges.
Sites to Avoid
- Forearm β constant water turbulence dislodges adhesive
- Inner thigh β friction from kick cycles causes premature detachment
- Lower back β swimsuit waistbands apply direct pressure
Waterproofing and Adhesive Strategies
Skin Preparation
Clean the site with 70% isopropyl alcohol and allow it to dry fully for 60 seconds before insertion. Skin oils are the leading cause of adhesive failure in water. Avoid moisturisers on or near the site for 24 hours prior.
Overlay Patches
Adhesive overlay patches (also called overtapes) cut to a doughnut or frame shape protect the sensor edges without covering the transmitter window. Popular options include rock-solid medical-grade acrylate patches. MDS Diabetes stocks a range of CGM overlay patches and skin-prep wipes designed specifically for active users and swimmers.
Liquid Skin Barriers
Applying a thin layer of liquid skin barrier (e.g., Skin Tac or Cavilon) under the sensor edge creates a waterproof bond layer. Allow it to become tacky (approx. 30 seconds) before pressing the sensor down.
During and After Swimming
Keep swim sessions under 30 minutes where possible to stay within manufacturer guidelines. Competitive or open-water swimmers should check sensor adhesion before each session. After exiting the pool, gently pat the sensor dry β do not rub. Rinse with fresh water if swimming in the sea or heavily chlorinated pools, as salt and chemical residues accelerate adhesive breakdown.
Receiver and Smartphone Considerations
Many CGM receivers are not water-rated at all β leaving them poolside is safest. Bluetooth range in water drops sharply; expect reading gaps during laps. Resume readings within seconds of surfacing. Waterproof phone pouches can keep your smartphone within Bluetooth range if you monitor during open-water events.