Many pre-retirees think they don't need to worry about healthcare because they anticipate care costs will be covered by Medicare.

But the reality is that Medicare makes seniors responsible for picking up a significant percentage of their cost of care. Seniors may face high deductibles, coinsurance costs, premiums, and coverage limitations.  

• Medicare Part A, which provides hospital coverage, has a $1,340 deductible; seniors hospitalized for more than 60 days during the year must pay a daily coinsurance cost. 
• Medicare Part B, which provides for routine care, has a 20% coinsurance cost.
• Medicare Part D, which provides prescription drug coverage, has a coverage gap you fall into once you've exceeded $3,750 in covered drugs in 2018. 

There are also many services Medicare doesn't cover, including hearing aids, long-term care, and dental care.

Because of coverage limitations, seniors must pay a portion of routine costs. In 2015, for example, The Commonwealth Fund found seniors with Medicare pay around 13% of healthcare expenditures out-of-pocket. This may seem fine if you have minor issues, but serious health problem are common, with 34% of current retirees responding to a Nationwide survey reporting health issues that interfere with retirement.

If you have a big problem, such as a stroke, could you afford 13% of $60,000 in treatment costs? What about $370,000 for care for you and a spouse? That's the amount the Employee Benefit Research Institute estimated a senior couple with high prescription use would need during retirement. And that doesn't even factor in long-term care, which could cost as much as $100,000 annually. 

The numbers above should have you convinced you need a plan to cover healthcare costs, but it can be hard to know where to start. 

First, if you're eligible based on having a high-deductible health insurance plan, contribute to a health savings account (HSA). You can contribute up to $6,850 in 2018, if you have family coverage, and can leave the money invested. 

Contributions to an HSA are made with pre-tax funds and the money can grow and be withdrawn without owing taxes, as long as it's used for qualifying health expenditures. If you contribute and invest when you're as young as possible and leave HSA money alone until you're a senior, you should have a generous nest egg to help cover care.

If you're already retired or nearing retirement, you may not have time to build up a big balance in your health savings account. If that's the case, consider whether your other retirement savings provides enough money to cover care costs. If it doesn't, you may need to work a little longer or look for a part-time gig in retirement to supplement your care expenditures or save for care down the road.

You can also look for ways to cut costs or find third-party sources of payment for the care you need. Purchasing a comprehensive Medigap policy is likely a good investment, and you should discuss with your doctor whether generic medications would work for you and ask for other suggestions your doctor may have for reducing costs.

Qualifying for Medicaid could also help you afford care costs by subsidizing Medicare premiums and paying for some services not covered by Medicare, such as routine nursing home care. While there are strict asset limits to obtain Medicaid, an attorney can help you to develop a plan that protects your wealth and still allows you to obtain coverage. 

Whatever approach you decide to take, today's the day to start making plans for how you'll cover healthcare costs as a senior. Your chances of a serious health issue go up dramatically as you age, and you don't want to be left unprepared, without the cash to cover you when you need care the most (see graph below).