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Home Reading Your CGM — Time in Range and the Numbers That Matter That Talk to Your Phone

Published October 2026 · Last verified October 2026

What the Screen Shows YouThree things, every time you glance at it.1A big numberYour sugar rightnow, in mg/dL —the live reading2An arrowWhich way it'sheading and howfast it's moving3A lineA graph of thelast few hours,with color bands4Reports laterTime in Range andGMI add up thedays for the doctorIllustration - a schematic, not to scale. Your setup may differ.
What the CGM screen shows you — the number, the arrow, and the line.
The Trend Arrows, Side by SideDirection and speed — your doctor tells you what to do about each.What it showsRoughly meansSteady arrowPointingsidewaysHolding fairlylevelSlanted arrowUp or down at anangleDrifting thatwayStraight arrowPointing up ordownMoving quicklyDouble arrowTwo arrowstogetherMoving very fastIllustration - a schematic, not to scale. Your setup may differ.
The trend arrows, side by side — direction, speed, and what each suggests.

A continuous glucose monitor fills your phone with numbers, arrows, graphs, and a report or two — and it's easy to feel like you need a medical degree to make sense of it. You don't. This guide walks you through what each part of the screen is telling you: the live number, the little arrows, "Time in Range," the GMI percentage, the daily and weekly graphs, and the alerts. It's about reading the display with confidence. What your numbers mean for your health, and your targets, stay with your doctor.

Bill Davis
Bill's Home Tech · Atwater, Ohio
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About $40 (as of mid-2026)
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They set targets — this is the tech side
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(330) 200-8042

A continuous glucose monitor fills your phone with numbers, arrows, graphs, and a report or two — and it's easy to feel like you need a medical degree to make sense of it. You don't. This guide walks you through what each part of the screen is telling you: the live number, the little arrows, "Time in Range," the GMI percentage, the daily and weekly graphs, and the alerts. It's about reading the display with confidence. What your numbers mean for your health, and your targets, stay with your doctor.

What's inside this guide

The printable PDF walks through 37 short chapters, in plain language. It also includes an everyday cheat sheet and at-a-glance pictures.

  1. The Live Reading in the Middle
  2. Why It Can Differ From a Finger Stick
  3. What the Trend Arrow Is For
  4. How Fast Is It Moving?
  5. Reading Where You're Headed
  6. The Graph of the Last Few Hours
  7. The Colored Zones on the Graph
  8. What "Time in Range" Means
  9. The 70-to-180 Band — and Why It's Yours
  10. How Much Time 'In Range' Is Good?
  11. Time Below and Time Above
  12. The GMI Percentage
  13. GMI and A1C — Used Together
  14. Your Average Glucose
  15. The 'Variability' Number
  16. How Much the Sensor Actually Caught
  17. Reading a Single Day's Graph
  18. The Weekly Pattern
  19. The One-Page Summary (AGP)
  20. The Smoothed Curve and Its Shading
  21. The High Alert
  22. The Low Alert and the Urgent Low
  23. An Alert Is Not an Ambulance
  24. Who Sets the Alert Levels
  25. How Your Numbers Reach the Office
  26. Patterns You Might Notice
  27. Reading Without Chasing Every Number
  28. A Low That Isn't — Pressure Lows
  29. When to Reach for a Finger Stick
  30. Reading It on a Phone vs. a Reader
  31. A Note for the Family Helper
  32. Common Worries, Answered
  33. A Few Myths, Cleared Up
  34. A Day in the Life of Reading It
  35. When to Call the Doctor — or 911
  36. Getting Comfortable in the First Week
  37. You Don't Have to Do This Alone

Get the printable guide

Everything above is a quick summary. The full, printable guide — the same words, laid out to read and keep by the computer — is a free PDF.

Download the printable PDF →

Last verified October 2026. Information accurate as of October 25, 2026.

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✍️ Every guide researched, written, and reviewed by Bill — your local Portage County tech.

Any prices or outside products mentioned in this guide can change over time — the details here were last checked August 2026 and this page is accurate as of October 18, 2026; please confirm current pricing before you buy. See how often we review our guides →