How to Read a CGM Report: AGP Graph, Time in Range, GMI and %CV

To read a CGM report, first check that it includes approximately 14 days of data with at least 70% sensor activity. Next, review Time Below Range (TBR), Time in Range (TIR) and Time Above Range (TAR). For most adults with diabetes, the general targets are TBR below 4%, TIR above 70% and TAR below 25%. Finally, use the Ambulatory Glucose Profile (AGP), Glucose Management Indicator (GMI) and coefficient of variation (%CV) to identify glucose patterns and fluctuations.

How do you read a CGM report step by step?

To read a Continuous Glucose Monitoring (CGM) report, start by checking data quality, then review low glucose readings, Time in Range (TIR), high glucose readings, and the Ambulatory Glucose Profile (AGP) graph. Finally, assess the Glucose Management Indicator (GMI), glucose variability (%CV), and daily glucose patterns.

Following a fixed order makes it easier to identify glucose fluctuations, recurring highs and lows, and periods when blood sugar stays outside the target range.

Here is an eight-step approach to understand how to read CGM report.

Check the CGM Data Quality

Before interpreting glucose patterns, check whether the report contains enough reliable data.

• Recommended monitoring period: Around 14 days of CGM data.

• Sensor data availability: At least 70% active sensor readings during the reporting period.

A report with insufficient or incomplete readings may not accurately represent usual glucose patterns. Check for missing data or gaps before drawing conclusions.

Check for Low Blood Sugar (Time Below Range

Review low glucose readings first because hypoglycaemia can require immediate attention, particularly in people taking insulin or certain diabetes medications.

Look at Time Below Range (TBR), which shows how much time glucose levels remain below the target range.

For most adults with diabetes:

• Below 70 mg/dL: Less than 4% of the day.

• Below 54 mg/dL: Less than 1% of the day.

Reducing time spent in hypoglycaemia is an important priority when reviewing CGM results. Repeated or prolonged low glucose episodes should be discussed with a healthcare professional.

Check time in range

Time in Range (TIR) indicates the percentage of time glucose levels stay within the recommended target range.

For most non-pregnant adults with type 1 or type 2 diabetes, the general target is:

• Target range: 70–180 mg/dL.

• Time in Range: More than 70% of readings.

• Equivalent time: Approximately 16 hours and 48 minutes per day.

A higher TIR generally indicates better glucose control. However, the appropriate target may vary depending on age, pregnancy, diabetes type, medication, and individual health circumstances.

Review High Blood Sugar (Time Above Range)

Next, examine Time Above Range (TAR) to understand how often glucose levels rise above the recommended range.

For most non-pregnant adults with diabetes, the general targets are:

• Above 180 mg/dL: Less than 25% of the day.

• Above 250 mg/dL: Less than 5% of the day.

Frequent glucose spikes may occur after meals, during periods of stress, or at certain times of the day. Look for recurring patterns rather than interpreting an isolated high reading.

Understand the Ambulatory Glucose Profile (AGP) Graph

The Ambulatory Glucose Profile (AGP) is one of the most useful parts of a CGM report. It combines glucose readings collected over multiple days into a single 24-hour visual summary.

It helps identify:

• Typical glucose levels throughout the day and night.

• Periods when glucose levels rise or fall.

• Variations in glucose readings at particular times.

• Patterns of recurring glucose fluctuations.

Ideally, the median glucose line should remain within the target range, while the surrounding variability bands should be relatively narrow. Pay particular attention to overnight readings, post-meal spikes, and recurring dips.

Review GMI and Glucose Variability (%CV)

After reviewing the AGP graph, check two additional metrics: Glucose Management Indicator (GMI) and glucose variability (%CV).

• Glucose Management Indicator (GMI): GMI estimates the HbA1c-equivalent glucose level based on average CGM readings. Compare it with the latest laboratory HbA1c result to understand whether the two values differ.

• Glucose Variability (%CV): This measures how much glucose levels fluctuate around the average. For most adults with diabetes, a %CV of 36% or lower is the recommended target.

A lower %CV generally indicates more stable glucose levels. A higher value may suggest frequent glucose fluctuations, even when average glucose levels appear satisfactory.

Remember that GMI is an estimate and may differ from laboratory-measured HbA1c.

Review Individual Daily Glucose Patterns

The overall AGP graph shows combined glucose patterns, but individual daily views help identify when specific fluctuations occur.

Look for recurring patterns such as:

• Glucose spikes after breakfast, lunch, or dinner.

• Overnight glucose drops or rises.

• Higher glucose levels on weekdays compared with weekends.

• Changes in glucose levels after physical activity.

• Repeated fluctuations at similar times each day.

Identifying these patterns can help patients and healthcare professionals understand how meals, activity, sleep, and other factors may influence glucose levels.

Discuss the Findings With Your Healthcare Professional

The final step is to review the CGM report with your doctor or diabetes care team. Share recurring glucose highs and lows, Time in Range, GMI, glucose variability, and any unusual patterns.

Your healthcare professional can use these findings alongside your medical history, medications, HbA1c results, and lifestyle factors to assess your glucose management.

Do not change insulin doses, diabetes medications, or treatment plans based on CGM readings alone. Always discuss appropriate adjustments with your healthcare professional.

What are the target ranges on a CGM report?

CGM target ranges help assess how well glucose levels are managed throughout the day. For most non-pregnant adults with type 1 or type 2 diabetes, the recommended goal is more than 70% Time in Range (TIR), less than 4% Time Below Range (TBR), and less than 25% Time Above Range (TAR).

The following table summarises the recommended CGM targets based on the International Consensus on Time in Range.

Source: International Consensus on Time in Range.

Do CGM targets differ for older adults, young people and pregnancy?

Yes. CGM targets vary with age, diabetes type, pregnancy and individual health risks. Older or high-risk adults may have less stringent glucose targets to reduce hypoglycaemia risk, while pregnancy requires a narrower glucose target range.

What about type 2 diabetes and gestational diabetes during pregnancy?

The 2026 American Diabetes Association (ADA) Standards of Care recognise the pregnancy glucose range of 63–140 mg/dL but state that evidence is insufficient to establish specific percentage targets for Time in Range, Time Below Range and Time Above Range in pregnant individuals with type 2 diabetes or gestational diabetes.

These targets are general clinical guidelines, not universal goals. A healthcare professional should individualise CGM targets based on medical history, treatment, age and risk of hypoglycaemia.

Ambulatory glucose profile interpretation: what does an AGP report show?

An Ambulatory Glucose Profile (AGP) is a standardised, one-page CGM report that combines approximately 14 days of glucose readings into a single 24-hour graph. It helps patients and healthcare professionals identify glucose patterns, fluctuations, and periods when blood sugar goes above or below the target range.

An AGP report typically includes:

• Data quality: Percentage of active CGM readings and monitoring duration.

• Glucose statistics: Average glucose, GMI and glucose variability (%CV).

• Time in ranges: Time Below Range (TBR), Time in Range (TIR) and Time Above Range (TAR).

• 24-hour glucose graph: Median glucose line and shaded variability bands.

• Daily glucose views: Individual daily readings to identify recurring patterns.

The AGP format allows patients and healthcare professionals to review the same glucose data and discuss possible treatment or lifestyle adjustments. Although most CGM manufacturers follow this standard format, report layouts may vary slightly between devices and apps.

How do you read an AGP graph?

To interpret an AGP graph, follow the median glucose line across the day, examine the width of the shaded bands, and check whether glucose readings move outside the target range of 70–180 mg/dL.

Each part of the graph provides different information:

Common AGP patterns and questions to discuss with your healthcare professional:

These patterns are not diagnoses. Your healthcare professional can interpret them alongside your daily routine, medication history and individual glucose targets.

What is the CGM time in range target percentage?

The standard Continuous Glucose Monitoring (CGM) Time in Range (TIR) target is above 70%, meaning glucose levels should remain between 70 and 180 mg/dL (3.9–10.0 mmol/L) for more than 16 hours and 48 minutes per day.

The 2026 American Diabetes Association (ADA) Standards of Care retain this general target for many non-pregnant adults with diabetes. However, individual targets may vary depending on age, health status and hypoglycaemia risk.

What is a good time in range percentage?

For most adults with type 1 or type 2 diabetes, a TIR above 70% is considered a good target. Older adults or people at higher risk of hypoglycaemia may have a more flexible target of above 50%.

Here is what different TIR levels mean:

Why does improving Time in Range matter?

• Small improvements count: A 5% increase in TIR (approximately 1 hour 12 minutes daily) can provide clinically meaningful benefits.

• TIR and HbA1c are related: A TIR of 70% roughly corresponds to an HbA1c of 7%, while 50% roughly corresponds to 8%. These are estimates, not interchangeable measurements.

• Improved glucose management: A 10% increase in TIR (2 hours 24 minutes daily) has been associated with an approximate 0.5–0.8 percentage-point reduction in HbA1c in different analyses.

• Potential reduction in complications: DCCT data linked every 10% decrease in TIR with a 64% higher risk of retinopathy progression and a 40% higher risk of microalbuminuria.

Remember: Time in Range is an important measure of glucose management, but it should be assessed alongside HbA1c, Time Below Range and glucose variability. Your healthcare professional can help establish a realistic target based on your individual health needs.

Source: International Consensus on Time in Range.

What are the time below range limits?

Time Below Range (TBR) measures how long glucose levels stay below the recommended range on a CGM report. For most adults with diabetes, the target is less than 4% of readings below 70 mg/dL and less than 1% below 54 mg/dL.

These limits help identify low blood glucose levels (hypoglycaemia) and reduce the risk of severe episodes.

For older adults or people at high risk of hypoglycaemia, the recommended target is stricter: less than 1% of readings below 70 mg/dL.

A few important points to remember:

• Prioritise low glucose: Reducing time below range comes before improving Time in Range (TIR) or reducing high glucose readings.

• Focus on daily duration: Thinking in terms of less than one hour below 70 mg/dL per day can make CGM targets easier to understand.

• Review longer-term patterns: Around four weeks of CGM data may help healthcare professionals assess hypoglycaemia exposure more reliably.

Repeated low glucose readings should be discussed with a healthcare professional. Treatment or medication adjustments should always be guided by individual clinical needs.

Evidence: International Consensus on Time in Range.

What is GMI on a CGM report?

Glucose Management Indicator (GMI) is an estimate of HbA1c calculated using average glucose readings collected by a Continuous Glucose Monitoring (CGM) device. It is expressed as a percentage and helps assess glucose management over the monitoring period.

GMI is calculated using the following formula:

GMI (%) =3.31+ (0.02392 into Mean glucose in mg/dL)

For example, an average CGM glucose level of 154 mg/dL gives a GMI of approximately 7.0%.

There is no universal GMI target. Goals should be individualised, although below 7.0% is a common example for many adults with diabetes.

What is the difference between GMI and lab A1C?

GMI and laboratory HbA1c both help assess glucose management, but they use different methods and monitoring periods.

Why can GMI and HbA1c results differ?

A difference between GMI and laboratory HbA1c is relatively common. Research has found that:

• Around 50% of patients had a difference of at least 0.5 percentage points between GMI and HbA1c.

• Around 22% had a difference of at least 1 percentage point.

• Chronic kidney disease (CKD) may increase this discrepancy. One study found a difference greater than 0.5 percentage points in 68.2% of people with CKD, compared with 42.2% without CKD.

Differences may also be influenced by red blood cell lifespan, anaemia, kidney disease and the CGM monitoring period.

Is GMI a replacement for HbA1c?

No. GMI complements laboratory HbA1c but does not replace it. HbA1c remains an important tool for assessing long-term glucose management and diabetes-related complication risk. Healthcare professionals should interpret both results alongside CGM metrics, medical history and individual health conditions.

Sources: International Consensus on Time in Range; Oriot et al., 2022; Perlman et al., 2021.

What is the CGM coefficient of variation target?

The CGM Coefficient of Variation (%CV) target is 36% or lower, indicating more stable glucose levels. A %CV above 36% suggests greater glucose variability, even when average glucose or HbA1c appears well controlled.

The coefficient of variation measures how much glucose levels fluctuate relative to the average glucose level.

It is calculated using this formula:

%CV = (Standard Deviation ÷ Mean Glucose) × 100

For people using insulin or sulfonylureas, a lower %CV target of below 33% may provide additional protection against hypoglycaemia.

Why does glucose variability matter?

Two people can have similar HbA1c levels but very different glucose patterns. For example, a 2020 Diabetes Care study involving older adults with type 1 diabetes found that participants with higher glucose variability spent a median of 84 minutes per day in hypoglycaemia, compared with 31 minutes among those with lower variability.

This shows why HbA1c alone may not provide a complete picture of glucose management. Reviewing %CV alongside Time in Range (TIR) and Time Below Range (TBR) helps healthcare professionals identify potentially important glucose fluctuations.

Source: International Consensus on Time in Range; Diabetes Care, 2020.

What should you do after reading your CGM report?

After reviewing your CGM report, identify recurring glucose highs, lows and fluctuations, and discuss them with your doctor or diabetes educator. The report can help guide decisions about meals, physical activity and diabetes management.

Here are a few steps to follow:

• Identify recurring patterns: Note when glucose levels repeatedly rise, drop or fluctuate, particularly after meals or overnight.

• Prepare for your appointment: Carry your CGM report, latest laboratory HbA1c results and notes about meals, physical activity, illness and medication changes.

• Set realistic goals: Work towards small improvements, such as increasing Time in Range (TIR) by 5%, while prioritising the reduction of low glucose episodes.

• Discuss treatment adjustments: Ask your healthcare professional whether changes to your medication, meals or activity routine are appropriate.

Regular CGM report reviews can help you and your care team identify patterns, track progress and make informed decisions about glucose management.

Frequently Asked Questions About CGM Report

Medical Disclaimer: This article is for informational and educational purposes only and should not be considered a substitute for professional medical advice, diagnosis or treatment. CGM results and glucose targets should be interpreted by a qualified healthcare professional. Do not change medications or treatment plans based solely on CGM readings.