Continuous Glucose Monitoring

A continuous glucose monitor (CGM) uses a sensor beneath the skin to estimate glucose in interstitial fluid, the fluid around tissue cells. It does not directly measure capillary blood glucose. Real-time CGM continuously transmits data for display, intermittently scanned CGM displays data when the user scans or activates the system, and masked CGM stores data for later review by the diabetes team. Available features, alert behaviour, approved wear sites, calibration requirements, and links to insulin pumps vary by device. Interstitial glucose and capillary blood glucose can differ while glucose is changing rapidly because blood glucose changes before interstitial glucose. Differences may be most noticeable after food, insulin, or exercise. Pressure on a sensor can also produce an unreliable low reading. The nurse therefore interprets the current value, trend arrow, recent pattern, symptoms, food, activity, and active glucose-lowering medication together. CGM helps reveal time in, below, and above a target range, the direction and rate of change, overnight events, and recurring patterns. These data support diabetes management; they do not independently diagnose diabetes or diabetic ketoacidosis. Diagnosis depends on the appropriate...