At the rate things are going, we'll be lucky if there is any health care system left at all in this country. But, barring that happening, in many cases, you are allowed to continue with your health care insurance that you have from your place of employment (COBRA) if you have such. Of course you might have to pick up the entire premium if your work doesn't provide for extended coverage after retirement. Otherwise you're on your own to find some kind of insurance, or just go naked until you reach Medicare age. You might also look into the medical-health care savings plan.
If you are impoverished--no problem; you probably qualify for Medicaid. I have talked to people who have moved to another country where they say health care is cheap. And then there is always the Lotto.
I was either lucky, or prudent; my employer covered me from the time I retired (at 59) until Medicare kicked in.