Most retirees rely on Medicare once they turn 65 to cover their healthcare expenses. The government-run program offers coverage for doctor visits, hospital stays, lab tests, prescription drugs, and more. But some people don't realize that Medicare covers few healthcare costs in full, and there are some expenses that it doesn't cover at all. If you aren't prepared to cover those costs on your own, you could be in serious trouble.

Below, I discuss four of the most common healthcare expenses that Medicare doesn't cover, along with ways that you can prepare for them, so you don't have to choose between your health and your financial independence.

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1. Dental care

Medicare, unfortunately, doesn't pay for teeth cleanings, dentures, fillings, nor any other type of dental work. Retirees will have to pay entirely out of pocket for their dentist visits unless they have a supplemental insurance policy that covers them.

Some Medicare Advantage plans -- which are issued by private health insurers -- include some dental coverage, or you could purchase a Medigap policy. These are also issued by private insurers and specifically cover healthcare expenses that Medicare doesn't. If you purchase one of these policies, though, it'll have its own deductible, premiums, and copay. This will increase your monthly healthcare expenses, but it should hopefully decrease the amount you pay out of pocket when you need to visit the dentist.

Another alternative is to enroll in a dental savings plan. This isn't insurance, but it can reduce your out-of-pocket costs for dental care. You pay a monthly fee to enroll, and in return, you get access to lower negotiated fees for your dental work.

If you have a health savings account (HSA) or flexible spending account (FSA), you can use the funds in them to pay for dental care as well. These accounts enable you to set aside pre-tax earnings, and as long as you spend the money for a qualifying medical expense, you won't pay taxes on it when you withdraw it either. Used in combination with a dental savings plan or supplemental insurance policy, they help you save even more.

2. Vision care

Medicare Part B covers some preventive and diagnostic eye exams, including glaucoma and macular degeneration tests, and routine eye exams for those who have diabetes.  And if you need cataract surgery, Medicare covers this as well as the cost of any vision-correcting products you need after the surgery. You will, though, still have to pay your deductible and a 20% copay unless you have a supplemental insurance policy that covers them.

However, if you're a healthy individual who needs glasses or contacts, all vision care expenses, including eye exams, glasses, and contact lenses, fall to you.

Some Medicare Advantage plans offer coverage for routine eye exams and other vision services. However, Medigap policies typically don't, so you'll have to look into a vision savings plan to help reduce your out-of-pocket costs. This is worth considering if you know you're going to have vision expenses in retirement, but if your eyesight is good, you may not feel the need to spend extra money on vision care.

3. Hearing aids

One of the most surprising omissions from the list of things that Original Medicare covers is hearing aids. You pay 100% of your out-of-pocket costs for hearing aids, batteries, and exams for fitting hearing aids. However, Medicare may pay up to 80% of the cost of a diagnostic hearing exam if your doctor orders it.

Medicare Advantage plans may cover hearing aids, depending on the plan you choose, but you'll still have to pay deductibles and possibly copays in addition to your monthly premiums. There are also some charities that provide free hearing aids to low-income individuals.

4. Long-term care

If you become physically or mentally incapable of caring for yourself in your old age, you may need to either hire someone to care for you or move to a nursing home. A semi-private room in a nursing home averaged $225 per day back in 2016, according to the most recent statistics from the U.S. Department of Health and Human Services, and your costs could be much higher if you live in an expensive area.

Medicare doesn't pay for either of these costs, so you may want to consider investing in a long-term care insurance policy. These specifically cover the costs of long-term care, but they're not cheap. Premium can average more $2,700 per year, according to LifePlans.

If you can't afford to pay that much for a policy, begin saving as much as you can in an HSA, if you're eligible for one. To qualify for an HSA, you must have a high-deductible health plan -- one with a deductible of at least $1,350 for a single adult or $2,700 for a family. In 2019, individuals may contribute up to $3,500 to HSAs, and families may contribute up to $7,000. People 55 and older may contribute an extra $1,000. Those contributions reduce your taxable income, and the funds in those accounts can be withdrawn tax-free to cover long-term care expenses.

Nobody can predict just what kinds of medical expenses you'll incur in retirement, but chances are, you'll need at least one of the services listed above. Planning for them today can help ease the burden on finances later.