Understanding CGM: Your Window Into Glucose Patterns
Continuous glucose monitors reveal patterns that finger pricks miss. Learn how to read trends, arrows, and what your data is really telling you.
What Is a CGM? A Continuous Glucose Monitor (CGM) is a small sensor worn on the body that measures glucose levels in interstitial fluid every few minutes. Unlike traditional finger-prick tests that give you a single snapshot, a CGM provides a continuous stream of data — revealing patterns that would otherwise remain hidden. Reading Trend Arrows Most CGM systems display trend arrows alongside your glucose value: → Stable — glucose is relatively flat ↗ Rising slowly — a gradual increase ↑ Rising quickly — rapid increase, often after meals ↘ Falling slowly — a gentle decline ↓ Falling quickly —
rapid drop, worth paying attention to These arrows tell you not just where your glucose is, but where it's heading. A reading of 120 mg/dL with a ↑ arrow paints a very different picture than 120 mg/dL with a → arrow. Time in Range (TIR) One of the most useful metrics from CGM data is Time in Range — the percentage of time your glucose stays within your target range (typically 70–180 mg/dL). Research suggests that higher TIR correlates with better long-term outcomes. Common Patterns to Watch Dawn Phenomenon A rise in glucose in the early morning hours (typically 4–8 AM), caused by hormonal
changes. Many people see their glucose climb before they even wake up. Post-Meal Spikes Most people experience some glucose rise after eating. The goal isn't to eliminate spikes entirely, but to understand which foods cause larger or longer-lasting elevations. Overnight Stability Looking at overnight glucose can reveal a lot about basal insulin needs and overall metabolic health. Getting Started If you're new to CGM, give yourself a few days to observe without trying to change everything. The data can feel overwhelming at first — but patterns will emerge. Focus on understanding before
optimizing.