Retirees should be prepared to cover all of their costs from their Social Security and savings. Most people think about expenses like housing, cars and travel when they predict their future financial needs. But, there's another important expense you cannot overlook: healthcare.

While you may assume Medicare will pay for everything you need, that couldn't be further from the truth. A recent study has shown the out-of-pocket costs of medical care could be far higher than you might imagine.

Retirees may need a six-figure nest egg for healthcare costs

According to the Employee Benefit Research Institute, a couple with high prescription drug needs will require $413,000 in savings earmarked for medical care to have a 90% chance of being able to cover all of their expenses. While Medicare offers coverage to seniors, there are copays and coinsurance costs as well as limits on what it pays for.

While $413,000 is on the high end of the scale for those who need more prescriptions than most, EBRI's data also showed even the typical senior will require a lot of money for medical care:

• The typical man needs $184,000 in savings to have a 90% chance of meeting out-of-pocket healthcare spending needs.
• A typical woman needs $217,000.
• A couple with a standard Medigap plan charging average premiums would require $351,000.

All of these are big numbers and you could find yourself quickly draining your 401(k) if you aren't prepared to pay up.

How can you be ready to cover healthcare costs in retirement?

Since medical care will be a huge expense for many seniors, it's important to prepare financially throughout your lifetime so you're ready when doctor visits begin and drug prescriptions must be filled.

If you're eligible for a health savings account (HSA), investing in one each year is the best way to prepare for senior care expenses. An HSA allows you to make tax-deductible contributions up to the annual limits. You don't have to use the money right away -- you can invest it each year and allow it to grow tax-free. And, as long as the funds are used for qualifying care expenses, you can even take tax-free withdrawals.

The triple tax benefits of an HSA are unlike any other account. Even tax-advantaged retirement plans like a 401(k) or IRA only give you a tax break either when you contribute or when you withdraw money, but not both. And, as a bonus, if you don't use your HSA for healthcare, you can take money out for any reason penalty-free after age 65. You'll just pay taxes on the withdrawals, similar to a 401(k).

Now, not everyone can invest in an HSA, as you need a qualifying high-deductible health plan to do so. If you aren't eligible, you may want to think about opening an IRA that you specifically dedicate to healthcare savings. You can contribute to this account along with your other retirement plans so you'll have the money you need for doctors and everything else your future self will require.

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