Medicare is a great program for retirees, but it ain't free. Even original Medicare has costs associated with it, and Medicare Advantage plans, which are issued by private insurance companies, can get quite spendy -- sometimes in ways you wouldn't expect. Before you sign up for such a plan, check the fine print for any of the following expenses to understand how much the plan will really cost you.

Monthly premiums

A Medicare Advantage plan's monthly premium is the most obvious cost associated with the plan; when you pull up a list of the plans available in your area, their premiums will be prominently listed in the summary page. As a rule of thumb, the better the coverage that the policy provides, the higher the premium will be -- the insurance version of "you get what you pay for."

If you're in good health and don't have a lot of medical expenses, it's usually best to go with a cheaper plan that offers a lower level of coverage. However, if you have significant medical expenses during most years, a higher premium plan will probably save you money overall because such a plan will cover more of your medical expenses. Before picking such an expensive plan, check its details to make sure it covers the kinds of medical expenses you expect to incur.

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Deductibles

Most Medicare Advantage plans have deductibles. This is the amount you have to spend out-of-pocket before the plan kicks in and starts covering the related expense. A plan with a high deductible is usually cheaper than a plan with a low one, so if you have an HSA or some other source of emergency cash and you don't have a lot of medical expenses, such a plan might work well for you. Just make sure that you have at least enough to meet the year's deductible tucked away in case a medical crisis arises.

Co-pays

Co-pays and coinsurance can make your Medicare Advantage policy a lot more expensive than you'd expect. A co-pay is your share of the cost for a particular medical expense, expressed as a dollar amount. For example, you might have a $15 co-pay for a visit to your primary care provider and a $30 co-pay for seeing a specialist. Coinsurance is similar, except that it's expressed as a percentage rather than a dollar amount. For example, you might be responsible for paying 40% of the cost of any lab tests.

If you have a lot of doctor's appointments, tests, and other medical expenses during the course of a year, co-pays and coinsurance can add up. Remember, until you meet your deductible you have to pay all the expenses; it's only after that point that co-pays and coinsurance become a factor. Before you make your decision about which plan to select for the year, do the math on the co-pays and coinsurance based on how many times you usually use the related services to see if a given plan really is a better deal than the others.

Out-of-network costs

Most if not all Medicare Advantage plans are based around provider networks. These providers contract with the insurance company selling your plan so you pay less for using those providers' networks. If your Medicare Advantage plan is an HMO, it won't cover out-of-network services at all except in an emergency. PPOs will cover out-of-network visits, but usually at a much higher cost to you.

Before choosing any Medicare Advantage plan, review the network providers in your area and make sure that you're comfortable sticking with those doctors and facilities. It's also wise to confirm that the network includes a wide range of specialists in your general area. Should you need to visit such a doctor, depending on where you live, there may be just one specialist of that type available. And if that specialist isn't in your network, you'll be out of luck.

Review your plan annually

During the open enrollment period each year, you'll be required to select a plan for the following year. Even if you intend to stick with your existing plan, you should review the plan and compare it with the others in your area before making a final decision. Medicare Advantage plans can change every year, so your existing plan may no longer be a good deal for you -- or another plan may have appeared in your area that's an even better fit. Spending a few minutes analyzing costs and coverages can easily save you thousands of dollars before the year is out.

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