The AGP Chart Explained: The Glucose Graph Your Endocrinologist Uses
Most CGM apps show you a line graph of your glucose over the last 24 hours. The Ambulatory Glucose Profile does something far more powerful — and it's the chart your doctor is actually looking at.
What is an AGP chart?
An Ambulatory Glucose Profile (AGP) is a standardised way of visualising CGM data that was developed by researchers and clinicians specifically to make glucose patterns legible at a glance. Instead of showing you one day's glucose as a wiggly line, the AGP takes multiple days of data and compresses them onto a single 24-hour axis — showing you not just one reading at 8am, but the statistical distribution of every 8am reading you've had over the period.
The result is a chart that shows you not just what your glucose was on a given day, but what it typically is at each time of day — and how much it varies.
How to read an AGP chart
An AGP chart has several layers, each showing a different statistical band of your glucose at each time point:
Median line
The middle line shows your 50th percentile glucose at each time of day — what you'd expect your glucose to be "on a typical day."
25th–75th percentile band (inner)
The darker shaded region. Your glucose fell within this band half the time at each time point. A narrow band means consistent glucose; a wide band means high variability.
10th–90th percentile band (outer)
The lighter shaded outer region. This captures most of your glucose readings, excluding only the most extreme outliers. Wide outer bands signal significant glycaemic variability.
What patterns should you look for?
Post-meal spikes: If the entire AGP rises sharply around typical meal times (7–9am, 12–2pm, 6–8pm), this indicates consistent post-prandial hyperglycaemia — a signal to look at meal composition or timing.
Overnight lows: A median that dips below the target band between 2–4am is a common pattern in people with Type 1 diabetes who run too much basal insulin overnight. This is almost impossible to catch from a daily line chart unless you specifically look at every night, but instantly visible on an AGP.
Dawn phenomenon: A characteristic rise in glucose in the early morning hours (4–8am) even without food, caused by the natural cortisol and growth hormone surge that occurs before waking. It appears as a rising median line in the pre-breakfast window.
Wide percentile bands: Large gaps between the 10th and 90th percentile bands indicate high glucose variability — even if your median looks good, you're spending significant time in both highs and lows. High variability is independently associated with worse outcomes.
Why the Dexcom app doesn't show you an AGP
The Dexcom app (Clarity) does offer AGP-style reporting, but only as a download report — not as a live, always-updated view in your daily dashboard. You have to log in to the Clarity web app, generate a report, and download a PDF. GlucoHome shows you an AGP updated in real time from your live Dexcom feed, visible every time you open your dashboard.
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