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If you’re on Medicare and you have to be admitted to the hospital, don't make the mistake of assuming your costs are covered. Find out whether your visit is being treated as an inpatient admission or a so-called observational stay. The distinction could cost you a lot of money—and it may even limit your access to a skilled nursing facility if you need follow-up care.

There's a growing likelihood that you may be given observational status—a kind of Medicare limbo that is akin to being an outpatient. Observational hospital visits soared 90% between 2006 and 2012, according to federal data.

The reasons for the shift are partly driven by Medicare’s efforts to restrain increases in health care spending, which include financial penalties for hospitals and doctors if they readmit too many patients. Classifying patient visits as observational helps to limit those readmission penalties—and in some cases, it may reduce costs. Medicare research in 2013 found savings to both Medicare and patients from observational stays vs inpatient stays lasting fewer than two nights.

Still, whether you see any cost savings will depend on your health care needs. Observational and inpatient stays are paid for by different parts of Medicare, even if the services provided are identical. Out-of-pocket costs for observational stays may be much higher, though patients and their doctors may be unaware of this until the bills are presented. Medicare does not require that patients be informed how their stay is classified, so some consumers have been hit with unexpected charges after being discharged.

Observational status may also limit your coverage for follow-up care in a skilled nursing facility. That's because Medicare coverage kicks in only after you spend at least three days as an admitted hospital patient. If your stay is classified as observational, it won't count toward this total. For many seniors, that rule has limited access to skilled nursing care.

A recent AARP report, based on an analysis of Medicare hospital visits in 2009, found that most visitors placed under observation required only outpatient services. But 10% of observational patients wound up with larger health care bills than they would have had if they had been admitted as inpatients. These patients were also likely to face higher costs for follow-up care.

So how do you know which category is really best for your finances? You don't. As the AARP report noted, inpatient status may mean lower costs if you need nursing care later. But for some short stays, your unreimbursed expenses may be lower with observational status. “Few Medicare patients will be able to anticipate into which group they are likely to fall,” the report said. “If they guess wrong, they are likely to face higher out-of-pocket costs.”

AARP advocates changing the rules for Medicare hospital stays, including capping out-of-pocket costs for observational stays and allowing that time to be credited toward skilled nursing care. Reforms are supported by several Medicare advocacy groups and the Medicare Payment Advisory Commission, which advises Congress on Medicare issues. Legislation to amend hospital stay rules is also pending.

Still, it may be years before any rule changes take place. So if you or your family members are on Medicare now, here are three guidelines for reducing the risks of observational status:

  • Find out your status. Demand that the doctors and hospital clarify how your stay is being classified. If you disagree with the decision, bring it up with your doctor right away. This is especially important if the patient is likely to need follow-up care at a nursing facility after their hospital visit.
  • Understand what's covered. Check out the differences in Medicare payment rules between inpatient expenses (covered by Medicare Part A) and observational or outpatient expenses (covered by Medicare Part B). You can find some of this information here and here.
  • Ask to use your own meds. Many hospitals do not allow use of medications brought from home. But if yours does, you’ll be able to sidestep the steep costs of hospital dispensaries.

Philip Moeller is an expert on retirement, aging, and health. He is co-author of The New York Times bestseller, “Get What’s Yours: The Secrets to Maxing Out Your Social Security,” and is working on a companion book about Medicare. Reach him at moeller.philip@gmail.com or @PhilMoeller on Twitter.

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