Medicare Advantage in San Mateo, CA

The figures above come from the Centers for Medicare & Medicaid Services 2026 plan year file, which CMS publishes each autumn before the October 15 to December 7 open enrollment window. A county premium reflects only the Part C portion that a plan charges. Most enrollees still pay the standard Part B premium of about $202.90 a month on top of it, so a $0 plan is rarely free in practice. The CMS star rating runs from one to five and weights more than 40 measures, including how well a plan manages chronic conditions, how fast it answers member calls, and how members rate their own care. A plan that holds five stars earns a special enrollment period that lets people switch into it at almost any time of year. Premiums alone can mislead a shopper, because a low monthly cost often pairs with a higher deductible or a tighter provider network. Federal rules cap in-network out-of-pocket spending at $9,250 for 2026, which is why two plans with identical premiums can leave very different bills after a hospital stay. Read our methodology for how each value here is sourced and computed.