What are Medicare Star Ratings, and do they matter when you choose a plan?

Short answer: Medicare Star Ratings are a 1-to-5 scale that Medicare assigns each year to Medicare Advantage plans and Medicare Part D drug plans, based on measures of care quality, member experience, complaints, and customer service. Five stars is the highest. Medicare publishes the ratings each fall, before the Open Enrollment Period, and shows them beside each plan in its plan finder. The ratings matter in two concrete ways: they are the only independent, published performance measure for these plans, and a 5-star rating opens a special enrollment window. What they do not measure is whether a particular plan covers your doctors, your prescriptions, or your budget.

Who rates the plans, and on what?

The Centers for Medicare & Medicaid Services (CMS) rates the plans, and the method is written into federal regulation at 42 CFR §422.166. The measures come from several places: clinical data on screenings, tests, and management of chronic conditions; member surveys about their experience with the plan; the volume of complaints and how many members leave; and how the plan handles customer service, appeals, and — for drug coverage — drug safety and the accuracy of its pricing information. CMS publishes the underlying performance data on its Part C and D performance data page, which is also where the annual release lands.

One detail changes how to read them: ratings are assigned at the contract level. An insurer's contract with Medicare may cover several plans in a region, and every plan under that contract carries the same stars. Two plans with the same rating can have different premiums, networks, and drug lists.

When are Star Ratings published?

Each October, ahead of the Open Enrollment Period that runs October 15 to December 7. The ratings you see during that window apply to the plans for the coming year. Medicare's joining a plan page lists the enrollment windows the ratings arrive ahead of.

What does a 5-star rating let you do?

It opens a special enrollment period. Under 42 CFR §422.62 for Medicare Advantage and 42 CFR §423.38 for Part D, a person may switch into a plan with an overall 5-star rating once during the period from December 8 through November 30 of the following year — that is, outside the regular fall window. It is a one-time-per-year election, and it only moves you into a 5-star plan; it does not open a general right to change plans.

What do Star Ratings not tell you?

• Whether your doctors are in the network. Network is plan-specific and not part of the rating.
• Whether your prescriptions are covered, and at what tier. That is the plan's formulary — we wrote about how one works in your plan's drug list.
• What you will pay. Premiums, deductibles, copays, and the out-of-pocket maximum are separate from the rating.
• Anything about Medigap or Original Medicare. Star Ratings apply only to Medicare Advantage and Part D plans. Medicare Supplement policies are not rated, and neither is Original Medicare itself.

So how should a Star Rating be used?

As one input, read alongside the things it doesn't cover. A rating answers the question how well does this plan operate for the people already in it. It does not answer is this plan built for my doctors, my drugs, and my budget — and those are the questions that decide most of the year's experience. A plan's Annual Notice of Change, its provider directory, and its drug list answer the second set.

If you'd like to talk any of this through with a person, that's a free, no-pressure conversation with a licensed agent — including the one that ends with “nothing to change.”