It depends how old you are at that point. If you're 65, then Medicare coverage kicks in. That's a huge relief.
If you're not yet 65, though, you must find - and pay for - your own health insurance coverage until you hit that birthday.
No matter what, don't let your health coverage lapse. If you suddenly have an accident and become ill, you could burn through your entire retirement savings stash in no time. And then you'll be in real trouble.