Using GRI to Deepen CGM Glycemic Data

As continuous glucose monitoring (CGM) becomes more central to diabetes management, healthcare professionals are faced with increasingly complex streams of data. Metrics such as Time in Range (TIR) provide valuable insight into glycemic patterns, but they may not fully capture the risks associated with hyperglycemia and hypoglycemia or the overall quality of glycemic control.

To fill this gap, the Glycemia Risk Index (GRI) was developed as a novel composite score that incorporates both highs and lows into a single, interpretable number. By offering a more complete picture of glycemic variation, the GRI enables clinicians to compare results across multiple CGM reports and patient groups.

According to the Diabetes Technology Society, the GRI is intended to help healthcare professionals—including certified diabetes care and education specialists (CDCESs)—interpret CGM data more effectively. When used alongside Ambulatory Glucose Profile (AGP) reports, it can provide valuable context for clinical decision-making and individualized care planning.

Why GRI?

The GRI was created to enhance CGM interpretation by integrating the severity and distribution of out-of-range glucose values. For example, two people may have similar TIR values, but their experiences with hypoglycemia or hyperglycemia can vary significantly. GRI addresses this by capturing not just time outside the target range but also the degree of risk associated with glucose levels in the hyper and hypoglycemic regions.

What Is GRI?

The Glycemia Risk Index is a single-number score ranging from 0 to 100 that summarizes glycemic patterns based on weighted CGM metrics, with lower scores reflecting less time in high- or low-glucose ranges and higher scores indicating greater glycemic variability with increased time spent in high and low ranges. The index draws from clinician consensus on the importance of different glucose ranges and prioritizing the extremes most associated with potential harm.

Key features:

• Weighs more severe hypoglycemia (<54 mg/dL) and hyperglycemia (>250 mg/dL) more heavily than milder levels.
• Separates hypoglycemia and hyperglycemia components, which can be analyzed independently or combined.
• Strongly correlates with experienced clinicians’ assessments of CGM tracings (r = 0.95).

How Is GRI Calculated?

GRI is based on four standard CGM metrics:

• VLow: % time <54 mg/dL
• Low: % time 54–<70 mg/dL
• VHigh: % time >250 mg/dL
• High: % time 181–250 mg/dL

The GRI Formula:

GRI = (3.0 × VLow) + (2.4 × Low) + (1.6 × VHigh) + (0.8 × High)

This calculation reflects aa weighted model based on input from over 330 clinicians who reviewed CGM tracings from 225 individuals living with diabetes (article cited in reference section)

Note: No need to memorize the formula—the DTS offers a free online calculator and a GRI Calculator app.

A Visual Guide

To help with interpretation, the GRI Grid plots:

• Hypoglycemia component (x-axis): VLow + (0.8 × Low)
• Hyperglycemia component (y-axis): VHigh + (0.5 × High)

The graph categorizes glycemic profiles into quintiles (Zones A–E), offering visual cues to:

• Compare patterns across individuals
• Track progress over time
• Identify individuals who may benefit from further support or consultation
• Understand the contributions of hypoglycemia and hyperglycemia to a person's GRI score to guide individualized care and education needs.

Sample grid example from DTS.

Clinical Relevance and Applications

The GRI is a practical tool that can be used across multiple settings:

• Population Health: Use GRI to stratify risk across patient panels, supporting triage and resource allocation.
• Individual Management: Monitor longitudinal GRI trends to gauge therapeutic effectiveness.
• Education and Decision Support: Facilitate patient education with an additional tool to AGP that provides an alternative visual and glycemic view and summary.
• Research and Clinical Trials: Incorporate an easily comparable composite number expressed by GRI that is reflective of real-world clinician judgment into outcome evaluations.

Comparing GRI to TIR

While TIR remains an important and well-validated metric, the GRI adds depth by accounting for the severity of both high and low glucose episodes. Since GRI and TIR are closely correlated (r = -0.91), the value of GRI cannot be dismissed.

Limitations

• GRI was developed using CGM data from insulin-treated adults; validation in children and during pregnancy is still needed.
• It is not intended to replace AGP interpretation but to supplement clinical decision-making.
• The index reflects clinician assessments rather than direct health outcomes—future studies may strengthen these connections.

Accessing the GRI

Access the  GRI Calculator

Read the full article with a description of the study undertaken to identify GRI in A Glycemia Risk Index (GRI) of Hypoglycemia and Hyperglycemia for Continuous Glucose Monitoring Validated by Clinician Ratings

Future Applications

The Glycemia Risk Index represents a potential tool for interpreting CGM data. Its integration of multiple data streams into a single, actionable score makes it particularly valuable as CGM use expands beyond endocrinology into primary care and population health settings.

CGM acceptance by individuals is increasing and an easy way to look at CGM data will enable wider acceptance among healthcare providers. The hope is for future research that will explore GRI’s ability to predict long-term outcomes and complications risk, evaluate user acceptance, and identify its application to individual and population health management. Dashboards that provide the composite GRI value as a metric along with the AGP will further improve and expand care opportunities both in-person and as a remote option. 

References

^{Klonoff DC, Wang J, Rodbard D, et al. A Glycemia Risk Index (GRI) of Hypoglycemia and Hyperglycemia for Continuous Glucose Monitoring Validated by Clinician Ratings. Journal of Diabetes Science and Technology. 2022;17(5):1226-1242. doi:10.1177/19322968221085273} 

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