Hospitals decide whether patients are admitted as inpatients or under observation status. But there are steps you can take to stay informed and help protect your wallet, says Keith D. Lind of the AARP Public Policy Institute:

Ask the hospital physician "What's my status?" every day that you're in the hospital, as it can change at any time.

If you think you have been incorrectly placed into observation status (remember that it does save money for many patients), ask the doctor to reconsider or ask if there is a hospital committee that can review your case.

Find out whether your own doctor agrees with the hospital physician.

If you need rehab but Medicare will not cover a skilled nursing facility, ask your doctor whether you qualify for similar care at home through Medicare's home care benefit, or for Medicare-covered care in a rehabilitation hospital.

If you expect to need nursing care after your hospital visit, investigate options. Your hospital social worker may be able to suggest rehab alternatives that do not require a previous three-night inpatient stay.

If you end up in a skilled nursing facility without having met the three-midnight hospitalization requirement, submit a claim anyway and see what happens.