Originally Posted by
MADPhil
If you are aged 65 or above you should be able to enroll in Medicare. If you have not contributed for 40 quarters while working in the US then you will have to pay a premium (probably about $500 per month) for Part A as well as the Part B premium. You would also need a supplementary policy and/or Part D and would thus need to evaluate how the total compares with alternatives. I don't know how the standard policies deal with someone who is 65 and not enrolled in Medicare.
Some countries (a small but material minority) have totalization agreements with the US, and so the 40 need not all be in the US.