San Mateo County, California — 2026 Medicare Advantage plans

What the star rating means. CMS rates every Medicare Advantage contract (the "H" number in the plan ID — all plans under it share the rating) on a 1-to-5 scale each October, from about 40 measures of care quality, member experience, complaints and appeals, customer service and, for plans with drug coverage, drug safety and pricing. The 2026 rating is largely based on performance measured in 2024.

5 Excellent4 Above average3 Average2 Below average1 Poor

Not rated means CMS published no overall rating — usually a contract too new to be measured or with too few members ("not enough data"); it is not a low score. A 5-star contract can be joined outside the normal enrollment windows (the 5-star Special Enrollment Period, Dec 8 – Nov 30). Medicare.gov flags contracts rated below 3 stars for three years running as low-performing. Stars describe the contract's past performance as CMS measured it; they are not a recommendation, and they do not tell you whether a plan's network, drugs or costs fit you.