Two stars, measuring different things
The quality-of-patient-care star is calculated from measures tracking whether patients improved — at walking, bathing, getting in and out of bed — and whether the agency delivered recommended care processes on time. It is about clinical results and process.
CMS separately publishes a patient survey star, drawn from the HHCAHPS survey of patients' own experience of care. That is a different dataset asking a different question, and this site does not currently show it. When someone cites a home health agency's star rating without saying which one, it is worth checking — an agency can look different on the two.
Half-stars are real steps
CMS publishes this rating in half-star increments from 1 to 5, so the scale has nine positions rather than five. A 3.5 is a genuine step below a 4, not a display artifact.
This site shows half-stars without rounding them away, on agency pages, in search results, and in the distribution exhibits on the hub and state pages. Rounding to whole stars would erase a distinction CMS itself draws — and would compress nine positions into five, which is a large loss for a rating that many agencies do not have at all.
The individual measures usually matter more
The star summarizes a subset of what CMS reports. The full measure set is grouped into outcomes (did patients improve), safety (falls with major injury, pressure sores), timeliness and process (was care started promptly), and hospital visits (potentially preventable hospitalizations or emergency-department use).
Which group matters depends entirely on the situation. Someone recovering from joint replacement is served by mobility improvement and timely start of care; someone with advanced heart failure is better served by the hospital-visit measures. The single star flattens all of that, which is why agency pages show the measures grouped by category.
Each measure carries the number of patients or episodes behind it. A percentage from a dozen episodes is far weaker evidence than one from several hundred, and direction differs by measure — improvement is better higher, falls are better lower. Both are labelled so a value is never read the wrong way round.
When there is no rating at all
CMS withholds a star when an agency has too few Medicare episodes to compute one reliably, or has been certified too recently to have a reporting history. Nationally, about a quarter of Medicare-certified agencies have neither a star nor a single reported measure.
A missing rating means small or new, not poor. But it does mean you have less public evidence, so the agency's own answers and your referring clinician's experience carry more weight for that agency than they would for one with a full record.
How likely you are to encounter this depends heavily on where you are searching — coverage ranges from nearly every agency rated in some states to well under a third in others. Our research on home-health data availability by state measures that spread.
Reading a rating in practice
Check first whether CMS reports anything for the agency at all; in provider search, the home-health mode filters to agencies with CMS quality data by default.
Use the star to shortlist, not to decide, then open the measure categories that match the reason for care and check the denominators before weighing any percentage.
Confirm current certification, services, and capacity with the agency and on Medicare's Care Compare. Agencies decline referrals when at capacity, and no public dataset records that.