What Is the GSD HEDIS Measure? A Complete Guide for Health Plans

GSD counts one lab result per member: the last one of the year. That changes how plans should approach the measure. A member who tested high in the spring, or who hasn't tested at all, can still count as controlled if they complete a new test before December 31 and the result comes back in range. Sending kits to members without a result and to members in poor control gives plans the best chance to capture as many good values as possible.

The GSD HEDIS measure tracks the percentage of members ages 18–75 with type 1 or type 2 diabetes whose most recent glycemic status (HbA1c or GMI) in the measurement year was below 8.0% or above 9.0%. Members with no result on file count toward the >9.0% poor-control rate.

What Does the GSD HEDIS Measure Require?

HEDIS (Healthcare Effectiveness Data and Information Set) is the National Committee for Quality Assurance's (NCQA) framework for measuring health plan performance. For Medicare Advantage plans, HEDIS results feed straight into Star Ratings and quality bonus payments.

The Glycemic Status Assessment for Patients With Diabetes (GSD) measure looks at members ages 18 to 75 with type 1 or type 2 diabetes. It reports two rates:

• Glycemic status <8.0% (good control)
• Glycemic status >9.0% (poor control, an inverse measure where lower is better)

Members in hospice or palliative care, members in institutional special needs plans, and members who meet both frailty and advanced illness criteria are excluded.

Why the Last Test of the Year Matters Most

GSD scores only the most recent glycemic status result in the calendar year. If a member has more than one result on the same date, NCQA uses the lowest one.

That's what makes this measure different. Earlier results don't lock anything in. A member who tested at 9.4% in March and 7.8% in October counts as controlled.

So a test near the end of the year does two jobs at once:

• It follows up on earlier interventions. Members who started a new medication or care plan in the spring have had time to improve, and a fall test captures that.
• It reaches members with nothing on file. The same outreach gets a first result for members who haven't tested yet this year.

One outreach effort can move both groups toward the <8.0% rate.

Why GSD Carries So Much Weight in Star Ratings

CMS scores GSD's poor-control rate in the Star Ratings measure called Diabetes Care – Blood Sugar Controlled. It's an intermediate outcome measure with a weight of 3, which puts it among the most heavily weighted measures in the Part C summary. Our 2026 Star Ratings breakdown explains how those weights shape a plan's overall score.

In practice, a small shift in GSD can move a plan's overall rating more than a bigger shift in a single-weighted measure.

Diabetes and Glycemic Control, by the Numbers

• 40.1 million people in the U.S. have diabetes, and more than 1 in 4 of them don't know it.
• Among U.S. adults with diabetes, the share with an HbA1c below 7% dropped from 57.4% in 2007–2010 to 50.5% in 2015–2018.
• The American Diabetes Association recommends HbA1c testing at least twice a year for people meeting their goals, and quarterly for everyone else.

The population is large and control has been getting worse, while GSD looks at only one number per member. That number needs to be current.

The Evolution of the Measure: From HbA1c to GMI

GSD started as an HbA1c-only measure. In 2024, NCQA revised and renamed it (it was formerly Hemoglobin A1c Control for Patients With Diabetes) to also accept a glucose management indicator (GMI). A GMI is an HbA1c estimate calculated from continuous glucose monitor (CGM) data.

That gives plans a second way to close the gap, but it only reaches members who wear a CGM. CGM use is growing quickly, but it's still the exception. A 2026 study in the Journal of Managed Care & Specialty Pharmacy found that CGM use among MA members with type 2 diabetes who use insulin rose from under 2% in early 2021 to about 1 in 6 by the end of 2023. For most members, an HbA1c lab result is still the path to closing the gap.

The Missing-Test Problem

Under NCQA's specification, a member counts in the >9.0% poor-control rate if their most recent result is above 9.0%, if the result is missing, or if no test was done during the measurement year.

So a member whose diabetes may be well managed, but who skipped their fall PCP visit, looks exactly like a member with an HbA1c of 11%. Their care may be fine. The gap is in the data. Getting a current result for that member is one of the fastest ways a plan can improve its GSD rate.

At-Home HbA1c Testing: Getting a Result on File

At-home collection removes what stops members from testing in the first place: booking an appointment, getting to a lab, and taking time off work. The member collects a few drops of blood with a fingerstick, mails the sample back, and a lab processes it.

The research backs this up. In a study published in Diabetic Medicine, HbA1c results from home-collected samples closely matched standard blood draws from a vein, and 60.7% of participants said they'd rather collect at home than visit their doctor.

Closing a GSD gap can take more than one kit per member. Some members won't return the first one. Others will test high in the spring and need a second test in the fall to show that they've improved. When a single gap can take two rounds of outreach, the process has to be easy for both the member and the plan.

With Ash's testing platform, plans can run that model under their own brand:

• White-labeled kits and outreach, so members see their health plan, not a vendor they don't recognize
• Email, SMS, and IVR outreach that works together, in English and Spanish. Members who get Ash's multi-channel outreach complete testing 2.4× more often than with single-channel method, which means more members with a lab result on file
• Clinician oversight of every test, from the order through review of lab results, with clinicians on record to act on abnormal results
• PCP connection, including capturing each member's PCP information and faxing lab results to their doctor
• Real-time reporting, so quality teams can see who has tested and who still needs outreach before the measurement year ends

HbA1c can also go into the same kit as other chronic condition screenings. Plans running KED programs can reach the same members for more than one diabetes gap with a single outreach.

For a closer look at this in practice, see how one national health plan activated 100,000 high-risk members for HbA1c screening.

Building a GSD Program That Closes the Gap

Plans making the most progress on the GSD measure plan around the calendar. Early in the year, clinical teams work with members who have high results. In the back half of the year, a second round of testing goes to those same members and to everyone without a result on file. That way the last lab result of the year reflects the progress members have made.

If your plan is behind with a few months left, our second-half HEDIS playbook walks through how to prioritize.

If your plan is working to improve GSD performance, Ash can help. Our gap closure programs bring at-home HbA1c testing to your members under your brand, with the outreach it takes to reach members who've been hard to reach. Talk to our team about building a program for your health plan.

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GSD HEDIS Measure FAQs

Which result counts if a member tests more than once?
The most recent HbA1c or GMI result in the measurement year. If there are several results on the same date, the lowest one counts.

What happens if a member has no HbA1c test during the year?
They count toward the >9.0% poor-control rate, the same as a member with a high result.

Does GMI count for the GSD measure?
Yes. A GMI calculated from CGM data counts toward GSD as long as the CGM date range is documented.

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