When Did Medicare Part B Begin? 
Medicare Parts A & B started in 1965 under the Social Security Act , but if you meant when is someone eligible for Medicare Part B then there are several answers . Most often somone is eligible for Part B when they turn 65 , enrollment period is 7 months , 3 months before month you turn 65 , the month of , and 3 months after . Someone may choose not to take Part B if they have other creditable coverage , such as employee or retiree benefits . There is a standard Part B premium , and it can be adjusted based on income . There are other instances when you can get Part B , such as if deemed disabled , after 24 months you will be eligible for Part B . 