Dialysis Star Ratings Explained
What Medicare's dialysis facility star rating measures, how stars are assigned, what "as expected" means, and the limits of the rating.
What the star rating is
When you look up a dialysis facility on Medicare's Dialysis Facility Care Compare tool, the most visible number is a rating from 1 to 5 stars. Medicare actually shows two separate star ratings for dialysis facilities: a Quality of Patient Care Star Rating, built from clinical quality measures, and a Survey of Patients' Experiences Star Rating, built from a patient survey (the ICH CAHPS survey). This guide focuses on the quality of care rating, which is the one most directories, including ours, display as the facility's "star rating."
The rating is calculated for CMS by the University of Michigan Kidney Epidemiology and Cost Center. Its purpose, according to a 2026 CMS technical expert panel report, is to make quality information easier for patients and caregivers to understand and to help them spot differences in overall quality when choosing a facility.
Which measures go into it
The quality of care rating combines several clinical measures into four groups, called domains:
- Domain 1, standardized outcomes: the standardized mortality ratio (deaths), standardized hospitalization ratio, standardized readmission ratio, and standardized transfusion ratio.
- Domain 2, vascular access for hemodialysis: the standardized fistula rate and the long-term catheter rate.
- Domain 3, dialysis adequacy and mineral levels: a combined Kt/V measure (how well waste is removed from the blood) and the share of patients with high blood calcium (hypercalcemia).
- Domain 4, transplant waitlisting: the percentage of patients on a kidney transplant waitlist and a standardized waitlisting ratio for new dialysis patients.
Scores are averaged within each domain, and the domains are then weighted to produce a final score. According to CMS's 2023 methodology update, Domain 3 counts half as much as the others. Facilities that provide only peritoneal dialysis have no vascular access measures, so they are rated on the remaining domains.
How scores become stars
Stars are assigned by comparing each facility's final score with cutoffs set during a "baseline" period. In the baseline, the distribution is fixed: the lowest-scoring 10% of facilities get 1 star, the next 20% get 2 stars, the middle 40% get 3 stars, the next 20% get 4 stars, and the top 10% get 5 stars. CMS reset the baseline this way starting with the October 2023 release.
Because later releases reuse those cutoffs, the share of facilities in each star level can drift over time. If facilities nationally improve, more of them can land in higher star levels. In other words, a star rating is a relative ranking against a reference point, not a pass/fail grade and not a guarantee of any particular outcome.
What "as expected," "better than expected," and "worse than expected" mean
Several measures on Care Compare, including mortality, hospitalization, readmission, and transfusion, are standardized ratios. Each compares what actually happened to a facility's patients with what would be expected for a facility with a similar patient mix. For example, the standardized mortality ratio is the observed number of deaths divided by the number expected, after adjusting for patient characteristics. The readmission ratio looks at unplanned hospital readmissions 4 to 30 days after a hospital discharge.
- A ratio of 1.0 means the facility's result matched what was expected.
- A ratio below 1.0 means fewer events than expected. For these four measures, lower is better.
- A ratio above 1.0 means more events than expected.
Care Compare also sorts facilities into categories: better than expected, as expected, or worse than expected. These labels reflect statistics, not just the raw number. As CMS's guide to its dialysis facility reports explains, a ratio can move above or below 1.0 from year to year purely because of random variation, especially at facilities with few patients. A difference is treated as meaningful only when it is unlikely to have happened by chance. So "as expected" generally means the facility's result could not be reliably told apart from the expected level. It does not mean the facility is mediocre, and a ratio slightly above or below 1.0 with an "as expected" label should not be over-read.
Limits of the star rating
- It reflects past data. The measures are built from data collected over earlier periods, and some measures update yearly while others update quarterly. Staff, leadership, and practices may have changed since.
- It does not cover everything that matters to you. The rating does not include shift times, transportation, how staff communicate, or whether the facility offers home training. Patient experience is rated separately.
- Small facilities are harder to measure. With fewer patients, a few events can swing a ratio, which is why many small facilities are labeled "as expected."
- Some facilities have no rating. A facility needs enough data in each domain to receive a rating. The Care Compare data dictionary includes a code explaining why a rating is not available.
- Risk adjustment is imperfect. Adjustments account for many patient factors, but no model captures every difference between patient groups.
How to use the rating well
Treat the star rating as a starting point for questions, not a final answer. Look at the individual measures behind it, compare nearby facilities that fit your schedule and location, and read the patient experience results. Then visit, ask questions, and talk with your kidney care team. This guide is general information, not medical advice.