On the current Medicare situation:

Here's How Much the Average Couple Will Spend on Health Care Costs in Retirement

By Elizabeth O'Brien @ Time.com/Money April 19, 2018

The average couple retiring today at age 65 will need $280,000 to cover health care and medical costs in retirement, according to an annual estimate by Fidelity, released Thursday.

The good news is that the figure is up only 2% from last year’s estimate of $275,000, a smaller-than-average increase. The bad news, of course, is that it’s still a huge number, reinforcing the fact that Medicare coverage is neither free nor completely comprehensive.

Fidelity’s estimate assumes that both members of the couple are 65 and on Original Medicare, not a private Medicare Advantage plan. The $280,000 includes premiums for Part B doctor coverage and Part D drug coverage, out-of-pocket costs such as deductibles, as well cost-sharing requirements for drugs. It also includes certain services and devices that Medicare doesn’t cover, such as hearing aids [....]

Kaiser Family Foundation on medical debt among the insured in 2015:

[....] as previous surveys have shown, insurance is not a panacea against these problems. Roughly one in five of those with health insurance through an employer (19 percent), Medicaid (18 percent), or purchased on their own (22 percent) also report problems paying medical bills. In fact, overall among all people with household medical bill problems, more than six in ten (62 percent) say the person who incurred the bills was covered by health insurance, while a third (34 percent) say that person was uninsured. Among those with private insurance (either through an employer or self-purchased), their plan’s deductible makes a difference in ability to afford health care bills, with those in higher deductible plans more likely to report medical bill problems than those in plans with lower deductibles1 (26 percent versus 15 percent) [.....]

from

The Burden of Medical Debt: Results from the Kaiser Family Foundation/New York Times Medical Bills Survey
Published: Jan 05, 2016