If your Freestyle Libre CGM readings are unusually high, there are several possible reasons. Some are related to actual blood glucose levels, while others could be due to sensor issues or external factors.
1. Physiological Reasons (Actual High Blood Sugar)
Food and Drink: Eating a high-carb meal or consuming sugary drinks can cause a spike.
Dehydration: Lack of water can concentrate glucose in interstitial fluid, leading to higher readings.
Illness or Stress: Sickness, infection, or stress can trigger the release of hormones (like cortisol), raising glucose.
Medications: Certain medications (e.g., steroids) can cause elevated glucose levels.
Dawn Phenomenon: Early morning rises in blood sugar due to hormone changes.
2. Sensor Accuracy Issues
Lag Time
The Libre sensor measures interstitial fluid, not direct blood glucose.
There can be a 5-10 minute delay between CGM readings and actual blood sugar.
This delay is more noticeable after meals, exercise, or rapid glucose changes.
Compression
If you slept on the sensor or put pressure on it, it may have read lower for a while.
When pressure is removed, a temporary spike can happen.
Sensor Warm-Up Issues
Readings in the first 12-24 hours after applying a new sensor can be inaccurate.
If your sensor is new, give it time to settle.
Calibration Issues
The Libre system does not require calibration, but sometimes it may give off readings.
3. External Factors Affecting Readings
Temperature & Environment
Extreme heat (saunas, hot showers, direct sunlight) can cause unreliable readings.
Cold weather may also slow glucose absorption in interstitial fluid, causing discrepancies.
If you’re seeing consistently high readings, your sensor may also be faulty.
In that situation, please contact us at contact@vively.com.au and we’ll investigate the issue for you.