Continuous Glucose Monitoring

A continuous glucose monitor (CGM) measures glucose in interstitial fluid, not directly in capillary blood. Interstitial glucose generally follows blood glucose closely, but it can lag when glucose is changing rapidly—after a meal, during exercise, after insulin administration, or while recovering from hypoglycemia. That lag explains a common clinical mismatch: a patient may feel shaky and diaphoretic while the sensor still displays a value that appears acceptable, or the sensor may continue to rise briefly after a correction dose has started working. The displayed value matters, but the direction and rate of change matter too. Most systems provide: - A current glucose value - A glucose trend graph - Trend arrows showing whether glucose is rising, falling, or relatively stable - Alerts for predicted or current hypoglycemia and hyperglycemia - Downloadable data that reveal recurring patterns CGM is a surveillance tool. It does not assess mental status, hydration, ketones, perfusion, or the patient’s ability to swallow. A low alarm in an alert patient who can safely take carbohydrate requires a different response than a low alarm in a confused patient...