Medicare is the primary health insurance for most people over age 65. Medicare Part A, which covers hospitals, is typically free. Medicare Part B charges a monthly fee that covers doctor visits and outpatient services. Most people pay for their Part B premium from their Social Security check. Each year, Congress and the Centers for Medicare & Medicaid Services (CMS) decide how much to charge for Part B. This year, the increase ($21.60/month) is the largest dollar increase in Medicare history and the largest percentage increase (15%) since 2016.