Also unlike traditional Medicare, the Medicare Advantage plans have a cap on the out-of-pocket spending that beneficiaries can incur in a year when they remain in-network: $6,700, with many plans offering a cap lower than that, according to HealthPocket.
While that cost ceiling is indeed an advantage for many enrollees, particularly those in poor health, who use medical providers and drugs more frequently than others, there is a key trade-off: narrow networks of participating doctors and hospitals. Unlike traditional Medicare, the Medicare Advantage plans can, and do, limit the providers it covers for enrollees.
And plans do change the makeup of their networks—as well as their cost-sharing structures—which are additional reasons why enrollees every year should check the design of their Medicare Advantage plan, and the designs of other such plans, experts said. Brand loyalty is often high among plan enrollees, but such loyalty can blind people to the fact that over time, their tried-and-true plan may end up costing them more money than if they had switched to another plan, which itself might have changed its design over time.
A Kaiser report on Medicare Advantage in May noted that as enrollment in Medicare Advantage plans grew, the average monthly premiums have declined, from $44 in 2010. But, the report added, "some evidence indicates that plans have made other adjustments to cut costs, for example, by increasing out-of-pocket limits, which could affect beneficiaries with relatively high health care expenses and by narrowing their provider networks."
That last point—the size of provider networks—can end up being a major issue for seniors.
"At the end of the day, health insurance is only as good as the hospitals and doctors that accept it," said Coleman of HealthPocket.
Another feature of Medicare Advantage, which is seen as a selling point for many, can be a downside for enrollees. This year, according to Kaiser research, the average Medicare beneficiary could choose from 18 Medicare Advantage plans. That amount of choice "can be very overwhelming," said Coleman.
While the amount of options can be daunting, switching within Medicare Advantage plans, or into such plans from traditional Medicare, can be worth the hours spent researching and comparing choices. Coleman said seniors should check to see if their preferred doctors and hospitals are included in a plan's network, whether their current medications are covered by the drug plan's formulary and to what extent, and to what extent enrollees would have to shell out for co-payments, co-insurance and deductibles.
A HealthPocket report issued in March found that for a "typical new Medicare enrollee," signing up for a Medicare Advantage plan "could save almost 20 percent over original Medicare and 45 percent over Medigap" supplemental insurance.
"For the average person, all things being equal, Medicare Advantage looks to be the best," Coleman said.
That report analyzed the costs for people in traditional Medicare and with Medigap coverage, compared to the costs for a Medicare Advantage enrollee if those people visited a specialist four times, a primary physician twice and was taking three commonly prescribed drugs.
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"In scenarios where a Medicare enrollee remains in-network for health care and no off-formulary medications are taken, it is difficult to imagine a situation where a $0 premium Medicare Advantage plan is not a less-expensive than Original Medicare with a prescription drug plan," the report noted.
That said, the HealthPocket report data is based on an estimate of the health services an enrollee will use during the coming year. While a person's current medical condition can be a helpful guide, it won't always lead to the optimal choice.
For example, a healthy senior who currently doesn't care much about the specialists covered by their current Medicare Advantage plan might care very much if they are diagnosed with cancer in June.
Coleman said that someone may say, "'I can afford a plan with lower premiums but higher out-of-pocket costs, because I don't expect to use the benefits.'"
"But that could come back to bite you if you have a cardiac event or stroke," Coleman said. "At the end of the day, you're making your best guess."
Another unknown is how the Affordable Care Act, also known as Obamacare, is going to change the landscape for Medicare Advantage plans and their premiums and design for enrollees.
The ACA is set to phase in more than $150 billion in direct cuts to the federal government's contribution to Medicare Advantage plans in coming years.
"Thus far, we have not seen large changes in plan premiums" as a result, Kaiser's Jacobson said.