About Low Glucose Readings

It’s not abnormal for glucose to intermittently dip below 70 mg/dL. In one study of healthy individuals wearing a CGM, 41% of people experienced glucose levels below 70 mg/dL in a 24-hour period.

Reasons you might be seeing low readings

• Calibration period
  • Low readings within the first 48 hours after applying your biosensor may happen during calibration.
  • Learn more: Calibration Period: The First 24–48 Hours of Your Sensor.
• Nighttime dips
  • Glucose can drop during sleep when energy needs are lower.
  • Pressure on the biosensor while sleeping can also cause false low readings.
  • Learn more: Why do my glucose levels go low during sleep?
• Post-meal lows
  • Dips below 70 mg/dL after a post-meal spike may suggest a reactive hypoglycemic response.
  • This can happen when insulin response is higher than needed after a high-carbohydrate meal.
• When glucose is actively changing
  • CGMs estimate blood glucose using glucose in interstitial fluid (the fluid between cells).
  • Readings can lag behind blood glucose by about 15 minutes, especially when glucose is changing quickly (after a meal or workout).
  • If you are comparing readings, compare when glucose is stable.
    • For example, compare in a fasted state or 2 to 3 hours after a meal.
• Accuracy margin
  • The gold standard for accuracy is a blood draw.
  • All at-home glucose monitors have error margins compared to that standard.
• Location
  • Placement can affect accuracy.
  • In general, place the biosensor on the fleshier part on the back of the arm, between the triceps and shoulder muscle.
  • Placement over muscle can lead to higher failure rates.