The first few days with a continuous glucose monitor can feel like a lot. There are numbers, graphs, colored zones, and little arrows pointing up, down, and sideways. It is completely normal to wonder what it all means and what, if anything, you are supposed to do about it.
The good news is that you do not need to be a data expert. This guide explains CGM trend arrows, time in range, and the reports your care team may review with you, so you can feel more at ease with your data and bring better questions to your appointments.
What CGM Trend Arrows Indicate
A trend arrow shows two things: the direction your glucose is moving and roughly how fast it is changing, based on recent readings.
- A sideways arrow generally means your glucose is fairly steady.
- An angled arrow (up or down) generally means it is rising or falling at a moderate pace.
- A straight up or down arrow generally means it is changing quickly.
- Double arrows, on devices that use them, generally mean a very rapid change.
The exact rate each arrow stands for is different from one device to another. Check your device's user guide to learn what the arrows on your system mean.
What trend arrows are not
Trend arrows are information, not instructions. Do not use trend arrows to decide how much insulin to take unless your care team has given you a specific, written plan for doing so. If an arrow worries you, or the number on screen does not match how you feel, follow the plan your care team has given you, which may include a fingerstick check. If you are new to CGMs, our CGM basics guide covers how the readings work.
Time in Range: The Big-Picture Number
Single readings go up and down all day. Time in range zooms out and asks a simpler question: over the last couple of weeks, what share of your readings were in your target zone?
In 2019, an international panel of diabetes experts published consensus targets for reading CGM data. For most adults with type 1 or type 2 diabetes, the suggested goals are:
| Glucose range | What it means | General goal for most adults |
|---|---|---|
| 70–180 mg/dL | Time in range | More than 70% of readings |
| Below 70 mg/dL | Time below range | Less than 4% |
| Below 54 mg/dL | Time well below range | Less than 1% |
| Above 180 mg/dL | Time above range | Less than 25% |
| Above 250 mg/dL | Time well above range | Less than 5% |
The "below 54" and "above 250" rows are included in the broader "below 70" and "above 180" rows, so they are not extra time on top.
Your targets may be different
These are general starting points, not personal rules. The same consensus suggests different targets for older adults and people at higher risk of low blood sugar, with more focus on avoiding lows. Pregnancy has its own targets, too. Your care team will set goals that fit your health, your treatment, and your life. Everyone's numbers and responses are different.
The AGP Report: Your Typical Day on One Page
Many CGM systems can create an ambulatory glucose profile, or AGP report. It is a standard one-page summary that many care teams use.
Instead of showing each day separately, the AGP layers all your days on top of each other. You will usually see:
- A summary of key numbers, such as time in range, time below and above range, and average glucose.
- A colored time-in-range bar that shows how your readings were split among the ranges above.
- A "typical day" graph with a middle line (the median) and shaded bands. Narrow bands mean your glucose was similar from day to day at that time. Wide bands mean it varied more.
- Daily glucose profiles, small graphs for each individual day.
The consensus recommends looking at about 14 days of data with a sensor worn most of that time, so the report reflects your usual patterns rather than one unusual day.
Patterns Worth Noticing
You do not need to fix anything on your own. The goal is simply to notice, and then talk it through with your care team. A few patterns people often bring to their appointments:
- Overnight: Does your glucose tend to drop, rise, or stay steady while you sleep? Do any low alerts happen at night?
- After meals: Are there certain meals or times of day when readings tend to go higher or stay up longer?
- Mornings: What do your readings look like when you wake up compared with bedtime?
- Activity days: Do your numbers look different on days you walk, work out, or are more active?
- Day-to-day changes: Are there wide shaded bands on your AGP at certain times of day?
Writing short notes alongside your data, such as meals, activity, sleep, and stress, can make these patterns easier to understand. Our guide on how to use a daily diabetes planner shows a simple way to keep notes like these.
Questions to Ask Your Care Team
CGM data is most useful when you review it together. Consider asking:
- What time in range goal makes sense for me right now?
- Which numbers on my AGP report matter most for my treatment?
- What should I do when I get a low or high alert?
- Are there any patterns here you want me to watch more closely?
- Should my alert settings be changed?
- How often should we review my CGM reports together?
For more ideas on getting ready, see what to bring to your diabetes appointment. Many care teams can review CGM data shared from your app before or during a visit, so ask how your clinic prefers to receive it.
When to Talk to Your Care Team
Contact your healthcare team if you often see readings below 70 mg/dL, if you get frequent low alerts (especially overnight), if your readings stay high for long stretches, or if your CGM numbers often do not match how you feel. Do not change your medications or insulin based on your CGM data alone. If you have symptoms of a severe low, such as confusion, fainting, or being unable to eat or drink safely, treat it as an emergency and follow the plan your care team has given you.
Your CGM data is not a report card. It is a set of clues that can help you and your care team make your plan work better for your real life.
