Star Ratings for Medicare Drug Plans: How to Compare Part D Plan Quality

Two Part D plans cover all of your parent's medications at roughly the same total annual cost. One has 4.5 stars. The other has 2 stars. The premium difference is $3 per month. Choosing the 2-star plan to save $36 a year is a mistake that won't show up until your parent's first coverage appeal takes three times longer to process.

Star ratings are the quality signal that the price comparison doesn't capture.

What Star Ratings Actually Measure

CMS assigns each Part D plan a rating from 1 to 5 stars based on performance across several categories:

Drug plan customer service: How quickly the plan answers calls, resolves complaints, and processes enrollment requests.

Member complaints and plan changes: The rate of formal grievances filed with CMS and how frequently the plan makes disruptive mid-year changes to its formulary or network.

Drug pricing and patient safety: Whether the plan prices drugs accurately at the pharmacy counter, provides medication therapy management for high-risk patients, and minimizes potentially harmful drug interactions.

Appeals processing: How quickly and fairly the plan handles coverage determination requests and appeals. A plan that routinely denies first-level appeals and takes the maximum allowed time at each level creates real problems for caregivers managing a parent's medications.

CMS updates star ratings annually, typically releasing new scores in October — right at the start of the Annual Enrollment Period.

Why 4+ Stars Matter for Caregivers

For caregivers specifically, the appeals and customer service categories carry disproportionate weight. If your parent's plan denies a medication or imposes step therapy, the speed and fairness of the appeals process determines whether an early decision is due in 24 hours for an expedited coverage determination or 7 calendar days for a standard redetermination.

Plans rated 4 stars or higher also qualify for CMS quality bonus payments, which often translates to richer benefit designs — lower copays, expanded formularies, or supplemental benefits. A 5-star plan gets an additional enrollment advantage: beneficiaries can join 5-star plans through a Special Enrollment Period at any time during the year, not just during AEP.

Plans rated below 3 stars may face CMS enforcement actions, including enrollment restrictions or contract non-renewal. A plan on a performance improvement plan today could be terminated next year — forcing your parent into an involuntary plan switch.

How to Use Star Ratings During Plan Comparison

When you run a comparison on the Medicare Plan Finder at Medicare.gov, star ratings appear alongside each plan's cost estimate. Here's how to incorporate them:

1. Sort by total annual cost first — this is still the primary filter.
2. Among plans within $50–100 of each other annually, prioritize the higher-rated plan. The quality difference is worth the marginal cost.
3. Never choose a plan below 3 stars unless it's the only option that covers a critical medication. Even then, check whether a formulary exception on a higher-rated plan would achieve the same coverage.
4. Check the trend. A plan that dropped from 4 stars to 3 stars is more concerning than a plan that climbed from 3 to 3.5. CMS publishes historical ratings so you can spot downward trajectories.

Star Ratings Won't Tell You Everything

The ratings don't measure formulary breadth or pharmacy network size — two factors that directly affect your parent's experience. A 5-star plan that doesn't cover your parent's blood thinner or doesn't include their pharmacy in the preferred network is still the wrong plan.

Use star ratings as a quality filter after you've confirmed the plan covers your parent's drugs at an acceptable cost. Think of it as the tiebreaker, not the primary criterion.

Our Part D selection guide walks through the full plan comparison process — from building the medication list to evaluating formulary restrictions, pharmacy networks, and star ratings in a single side-by-side worksheet.

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