Studies on Glucose Sensors and Scuba Diving
Data from Diabete Sommerso®
Until a few years ago, scuba diving was discouraged for people living with type 1 diabetes, mainly because of the risk of hypoglycemia underwater.
Today, thanks to rigorous safety protocols, recreational diving has become possible for many people with diabetes.
Between 2023 and 2025, Diabete Sommerso® conducted several studies to assess the reliability of the main continuous glucose monitorin (CGM) in the specific context of repetitive diving. The results show that CGM sensors are a valuable tool for monitoring glucose trends, but none can yet completely replace capillary blood glucose testing before and after dives.
The Three Main Studies
1. FreeStyle Libre 3 vs Dexcom G7
This first study compared the performance of the FreeStyle Libre 3 and the Dexcom G7 during more than 200 dives carried out by 13 people with type 1 diabetes during the Blue Week in the Maldives in 2023.
Main Results
- The FreeStyle Libre 3 was overall more accurate than the Dexcom G7
- The difference was particularly noticeable when glucose levels were within normal or high ranges
- However, neither sensor achieved the level of accuracy required to completely replace capillary blood glucose measurements
Conclusion
Both systems can help monitor glucose trends, but fingerstick glucose testing remains essential for safe diving.
2. The Effect of Dexcom G7 Calibration
The second study investigated the impact of daily calibration of the Dexcom G7 during repetitive diving.
Eight divers with type 1 diabetes participated in a liveaboard trip around Elba Island in 2024 while simultaneously wearing two Dexcom G7 sensors, one on the arm and one on the abdomen, and calibrated the sensor using capillary blood glucose levels every morning fasting, when blood glucose levels were stable.
Main Results
- Calibration significantly improves the accuracy of the Dexcom G7
- Performance was better when the sensor was worn on the arm
- Despite this improvement, accuracy remained insufficient to completely replace capillary blood glucose testing
Conclusion
For divers using the Dexcom G7, daily calibration can provide more reliable data, but it does not eliminate the need for glucose meter verification.
3. Evaluation of the Medtronic Simplera
The third study evaluated the Medtronic Simplera sensor during 90 dives performed during the Blue Week in Madagascar in 2024.
Main Results
- Good correlation with capillary blood glucose measurements
- The sensor tended to underestimate glucose levels
- Accuracy was comparable to that of the FreeStyle Libre 3
Conclusion
The Simplera is also a useful tool for monitoring glucose trends before and after dives, but it cannot yet replace capillary glucose testing.
Comparative Table of Sensors
| Sensor | Participants | Number of Dives | Mean Error (MARD) |
| FreeStyle Libre 3 | 13 | 202 | 14.2% |
| Dexcom G7 Uncalibrated | 13 | 202 | 31% |
| Dexcom G7 Calibrated | 8 | 68 | 11% (arm) / 16% (abdomen) |
| Medtronic Simplera | 10 | 90 | 14.3% |
Key Takeaway
A sensor is generally considered accurate enough to replace capillary glucose testing when its mean absolute relative difference (MARD) is below 10%.
None of the systems studied reached this threshold in the context of repetitive diving.
20 Years of Experience from Diabete Sommerso®
Since 2004, Diabete Sommerso® has collected data on scuba diving among people living with type 1 diabetes.
The results published after 20 years of experience include:
- 68 divers with type 1 diabetes
- 1,179 dives analyzed
The safety protocol includes:
- Multiple glucose checks before diving (60 – 30 – 10 min before)
- Stable glucose values before immersion between 8.3 – 13.9 mmol/L (150 – 250 mg/dL)
- Careful monitoring after exiting the water
Observed Results
- Post-dive hypoglycemia is rare (1.7%)
- No severe episodes have been reported
- An average decrease in blood glucose during dives was observed
Conclusion
The collected data show that scuba diving can be practiced safely by people with type 1 diabetes:
- When they are properly trained
- When glucose control is well managed
- When safety protocols are strictly followed
Beyond safety, this experience also demonstrates positive effects on:
- Independence
- Self-confidence
- Quality of life
General Conclusion
Continuous glucose monitoring systems are now an important aid in preparing for and monitoring dives in people living with type 1 diabetes.
However, studies conducted by Diabete Sommerso® show that no sensor is yet accurate enough to completely replace capillary blood glucose testing in the context of repetitive scuba diving.
Strict adherence to safety protocols therefore remains essential to ensure safe diving practices.