Continuous Glucose Monitoring

A continuous glucose monitor, often shortened to CGM, samples glucose in the fluid between cells rather than drawing blood for every reading. The sensor sends estimates to a reader or connected device at regular intervals. This produces a time series that can show direction, timing, and variability in glucose patterns. Because interstitial fluid and blood are different compartments, a sensor value may lag behind a rapidly changing blood glucose value.

CGM reports commonly organize information as traces, daily overlays, ranges, and summaries. These displays can help a qualified practitioner interpret how readings relate to meals, activity, sleep, stress, medication, and sensor conditions. A single rise or fall does not establish a diagnosis. Sensor placement, compression during sleep, hydration, calibration requirements, and device limitations can all affect what appears on the graph.

The useful question is usually not whether every line is perfectly flat, but what repeatable patterns exist and whether they fit the wider clinical picture. Laboratory measures such as fasting glucose and HbA1c describe different time frames, while fasting insulin and HOMA-IR address related aspects of glucose regulation. Each measure has limits, and none should be interpreted without context.