This is a question often asked me by people getting ready to receive or who already have Medicare.
Well here it is simplified… your options once you receive Parts A and B with Medicare.
1) Absolutely Nothing!
2) Take out a stand-alone drug plan and keep Medicare only.

Remember, Medicare is an 80/20 plan, which means you are responsible for 20% of what Medicare covers, and there is no cap.
(You are responsible for 100% of what Medicare does not cover)—If you do not take a drug plan out and you do later on, you will be penalized 1% of the national average drug cost per drug plan per month if you do not have a drug plan for the rest of your life. (About 35 cents every month)
3) To take out a part C, called a Medicare Advantage, such as a Humana, BCBS, UHC. This becomes your primary insurance now, and sets co-pays, maximum out-of-pocket costs, and helps control the 20% of Medicare you are responsible for paying.
4) Take out a supplement and a drug plan. A Medicare Supplement will pay the portion of Medicare that you are responsible for paying.
5) Keep your coverage from your workplace or spouse if it is available.