A combination of giving patients more information about their conditions and better managing their medications can slow the revolving door of Medicare patients in and out of hospitals by about 20%, a study released Monday by Harvard University shows.

Researchers determined that physicians often did not have a complete list of medications that other doctors had prescribed for a patient, so they prescribed drugs that reacted badly with the patient’s other medications, said Randi Berkowitz, a geriatrics instructor at Hebrew Rehabilitation Center. Most often, Berkowitz said, patients did not understand the care they were receiving or needed.

“They think they’re sicker than they are, or they don’t understand how sick they are,” Berkowitz said.

This information can help hospitals better cope with part of the health care law that will force them to repay Medicare for the cost of patients who are readmitted to a hospital within 30 days of their previous stay, researchers said. Previous research showed that one in five Medicare patients returns to the hospital within 30 days of a previous admission.

It costs Medicare $17 billion a year to pay for patients who are readmitted to the hospital within 30 days of their last stay.

The change takes effect in October 2012, and includes readmissions for heart failure, heart attacks and pneumonia within 30 days of a previous stay. More diseases will be added to the list.

Read more about informed patients and healthcare.