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Is the magic date for your retirement approaching? Or perhaps you have already achieved that major life milestone? Retirees who have planned well can look forward to their hard-earned rewards. One of the biggest headaches with retirement, though, can be dealing with health insurance. Here are five important facts about health insurance that every retiree should know.

1. Your health insurance needs go beyond just health insurance.

Whether you're retired or still working, health insurance won't cover all of your health-related needs. Most dental, hearing, and vision services aren't included in health insurance policies. Medicare, for example, covers only dental services that are part of an otherwise covered procedure (like facial surgery) or in special situations such as extractions needed related to jaw cancer.

Many retirees opt to pay for dental, hearing, and vision services on their own and forgo insurance. That's a reasonable choice for some, but know that the out-of-pocket costs could be higher than you'd like.

Sometimes the decision to go without insurance leads to also going without preventive care. According to a 2010 Kaiser Family Foundation study, 34% of Medicare beneficiaries had not visited a dental provider in the past two years. In addition, 22% had not gone to a dentist in the last five years.  Such choices can be penny wise and pound foolish, though, since more serious health issues can often be identified early or even avoided by appropriate preventive care. 

2. Traditional Medicare probably won't be enough by itself.

Medicare serves as the cornerstone of most retirees' health insurance. It's important to know what Medicare covers  -- and what it doesn't. 

Medicare Part A pays for in-patient hospital stays, lab tests, surgeries, and doctor visits. It also covers some skilled-nursing-facility and home-health costs. Most retirees won't pay premiums for Medicare Part A.

Medicare Part B covers things like durable medical equipment, preventive services, mental healthcare, surgical second opinions, and a limited number of prescription drugs. You will have to pay a premium for Medicare Part B based on your annual income, from $121.80 to $389.80 per month. 

If you enroll in traditional Medicare Part A and Part B coverage, you'll probably want to also consider Medicare Supplement Insurance (also called Medigap). These policies are sold by private insurance companies and help pay some of the costs that Medicare doesn't cover, including copayments, coinsurance, and deductibles. Some Medicare Supplement plans also pay for certain services that Medicare doesn't cover.

Note that we haven't mentioned prescription drugs, except for a few limited drugs covered by Medicare Part B. Prescription drugs can be a significant expense for retirees. You can buy a Medicare Part D insurance policy from a private insurer to cover part of your prescription drug costs. Alternatively, you could choose to buy a Medicare Advantage policy from a private insurer. Medicare Advantage plans provide Part A and Part B benefits. Most also include prescription drug coverage. 

3. Employers' retiree health insurance isn't a given.

Many employers have "retired" their health insurance plans for retirees. According to the Kaiser Family Foundation, the share of large companies with 200 or more workers offering retiree health insurance has dropped from 66% in 1988 to 28% in 2013. 

If your employer offers retiree health insurance, consider yourself fortunate. However, know that what you have now might change in the future. Employers don't have to provide retiree insurance. They can change benefits or premiums at any time. And they can drop the coverage altogether.

Retirees who do have employer-sponsored health insurance should make sure to read the fine print of their policies. In particular, learn how your employer's retiree coverage works in conjunction with Medicare. Some employer-sponsored retiree coverage might pay only when your out-of-pocket costs hit a specified amount. Other plans could have other limitations that impact how much you pay for healthcare. 

4. There are plenty of health insurance options if you retire before age 65.

Our discussion so far has focused primarily on those who retire at age 65 and are eligible for Medicare. However, many Americans retire before age 65. If you're in that group, what are your health insurance options?

Perhaps the first alternative to check out is obtaining COBRA coverage through your employer. You can receive COBRA coverage for 18 months after leaving employment. This could be a good option particularly if you turn 65 (and therefore become eligible for Medicare) within 18 months of your retirement date.

Don't forget the Obamacare exchanges, either. You could be eligible for a federal subsidy to help defray the costs of health insurance. And don't worry if you're not retiring during an open enrollment period. Losing your health coverage as a result of retirement qualifies you for a special enrollment period (as long as you don't have other retiree health coverage).

5. Your total costs will likely be far greater than your insurance premiums.

You might not like the high price tags of your insurance premiums for Medicare Part B, Part D, Medicare Supplement, or Medicare Advantage plans. Unfortunately, I have bad news: Those premiums are only part of your total health insurance costs in retirement.

Retirement healthcare planning company Healthview Services released a report in 2015 that shows just how much the total costs can be. This report projected the lifetime healthcare expenses for a 65-year-old couple, assuming that the individuals had health, prescription drug, and dental insurance as well as Medicare Supplement Insurance.

For men, the projected lifetime costs totaled over $275,000. For women, the lifetime costs were estimated to be just under $295,000. Insurance premiums made up the biggest part of those projected costs. However, over one-quarter of the expenses were out-of-pocket costs in addition to the premiums. The biggest chunk of those additional costs came from hearing and vision services.

According to Healthview Services' projections, the earlier retirement years won't be as costly as the later years. Ten years after retirement, though, the expected annual healthcare costs are nearly twice as much as the first five years following retirement. The bottom line here is that retirees need to plan for significant healthcare-related spending on top of their insurance premiums.