| MARD Accuracy | 8.2% |
| Sensor Wear Duration | 10 days + 12-hr grace period |
| Reading Interval | Every 5 minutes |
| Warm-up Time | 30 minutes |
| Calibration Required | No (optional) |
| Approved Wear Site | Back of upper arm |
Key Takeaways
- Compression lows are false hypoglycemia alerts caused by physical pressure on the G7 sensor
- Most common during sleep when you roll onto the sensor site
- Always verify with a fingerstick before treating a suspected low
- Proper placement and sleep positioning can significantly reduce occurrences
What Are Dexcom G7 Compression Lows?
A compression low occurs when external pressure on the Dexcom G7 sensor restricts interstitial fluid flow around the filament, causing artificially depressed glucose readings. The sensor misinterprets reduced fluid contact as low glucose, triggering false hypoglycemia alerts β even when your actual blood sugar is normal or elevated.
How Compression Lows Happen
The Physiology
The G7 measures glucose in interstitial fluid via an electrochemical filament. When pressure collapses the tissue around the sensor, fluid is temporarily displaced, starving the electrode of glucose molecules. Readings can drop 20β60 mg/dL below true values within minutes of sustained pressure.
Common Triggers
- Sleeping directly on the sensor (most frequent cause)
- Tight clothing, waistbands, or bra straps pressing on the site
- Seatbelts during long drives
- Sports equipment or backpack straps
- Lying in one position for extended periods
Identifying a Compression Low
| Indicator | Compression Low | Real Hypoglycemia |
|---|---|---|
| Onset speed | Very rapid drop | Gradual decline |
| Symptoms present | Usually none | Sweating, shakiness |
| Recovery after repositioning | Yes, within 5β15 min | No |
| Fingerstick confirms | Normal BG | Low BG |
Fixes and Immediate Solutions
During a Suspected Compression Low
- Reposition immediately β remove all pressure from the sensor site
- Wait 10β15 minutes β readings typically normalize as interstitial fluid returns
- Confirm with a fingerstick β always verify before treating with carbohydrates
- Do not stack carbs β treating a false low causes real hyperglycemia
Prevention Strategies
Optimal Sensor Placement
The Dexcom G7 is FDA-approved for the upper arm (back), but placement matters. Choose sites with adequate subcutaneous fat and avoid bony prominences. Rotating sites reduces tissue fatigue and improves accuracy.
Sleep Positioning Tips
- Wear the sensor on your non-dominant or less-slept-on arm
- Use a sensor armband sleeve to distribute pressure evenly
- Try a small foam donut pad around the sensor while sleeping
- Back sleepers experience fewer compression lows than side sleepers
Clothing and Gear Adjustments
- Avoid tight sleeves over active sensors
- Choose loose-fitting athletic wear during exercise
- Adjust bag straps to avoid sensor sites
Dexcom G7 Specs Relevant to Accuracy
- MARD: 8.2% (best-in-class accuracy)
- Warm-up time: 30 minutes
- Wear duration: 10 days + 12-hour grace period
- Reading interval: Every 5 minutes
- Calibration: Optional (not required)
When to Contact Dexcom or Your Care Team
If compression lows occur frequently regardless of positioning, the sensor filament may be kinked or placed incorrectly. Dexcom's warranty covers sensor failures β contact support if inaccurate readings persist. MDS Diabetes carries the full range of Dexcom G7 sensors and accessories including protective sleeves that help minimize compression events.