[ossiblue]

Tobra has summed it up pretty well, but just a few other details.

The sign up deadline is for Medicare, Part B, which is optional but, IMO, really essential. That is the part for doctor's care, visits, etc. That Part B requires you to pay a premium each month, currently $140 for the lowest rate. That premium will be larger depending on your retirement income and filing status.

In addition to that premium, you may need a supplemental policy as Tobra mentioned to pick up the 20% that isn't covered by the Medicare B option. This is where the private companies come into play, offering different policies/coverage for different amounts, for that supplemental coverage only. Typically, you pay a separate premium as payment for their coverage. Their coverage only kicks in to cover expenses not covered by the Medicare B coverage, and the amount you pay, in addition to their monthly premium, is based on their co-pays and deductibles for you. This type of supplemental policy does not cover drugs, that's Part D, and requires a separate policy.

Medicare Advantage Plans cover both supplemental coverage and drugs. Many are HMO, have restrictions, and receive your Part B premium as partial or total payment for the plan. For example, I have Kaiser Medicare Advantage, pay no money beyond my monthly (actually quarterly) payment to SSS, and I have complete coverage for hospital, doctors, and drugs. Used to have an Anthem Advantage plan that had similar coverage for doctors and drugs, but was a PPO set up and, originally cost an additional $40/mo. That rose to over $160/mo. within two years so I switched to the Kaiser Plan.

Simply put:

Medicare Part A only=You pay nothing but it is only for hospitalization, basically. Everyone who qualifies receives this benefit, free.

Medicare Part B=you pay a monthly premium to SSS for doctor visits, etc. but it only covers 80% of the charges.

Medicare B w/supplemental plan=You pay SSS premium, plus a premium a private company for coverage of your 20% obligation, plus co-pays and deductibles out of pocket. You need another policy to cover drug costs with the additional premium, but some plans offer it as part of their premium costs.

Medicare Advantage plan=You pay monthly SSS premium and Advantage plan typically accepts that amount for their supplemental coverage for your 20% obligation. Includes a drug plan as well at no additional cost, typically.