A nationwide survey revealed that nearly one in 15 older Americans or 2.2 million people are exposing themselves to risks such as bleeding and muscle weakness because they take unwise combination of drugs, non-prescribed medicines and sometimes even dietary pills with them. The findings were published in the Journal of the American Medical Association.

For the study, Dr. Stacy Tessler Lindau of the University of Chicago Medical Center in Illinois teamed up with Dima Qato, a pharmacist and researcher at the University of Chicago. They used data from a national survey of adults aged 57 to 85 and interviews with nearly 3,000 people in their homes to get a read on the medications they used on a regular basis.

The researchers found that 91 percent of US adults, about 50.5 million, used at least one medication regularly. Prescription medicines were used by 81 percent of adults, or 44.9 million older Americans. Most medications were used by those 75 to 85 years old.

“Some may assume that, just because a drug is available without a prescription, it’s safe,” Qato said.

In addition, almost 50 percent of older adults used at least one over-the-counter medication or dietary supplement. More women than men used prescription medications and dietary supplements.

Moreover, 68 percent of older adults used prescription drugs plus over-the-counter medications or dietary supplements. Among those combining drugs, 4 percent were in danger of having an adverse drug reaction.

The most common adverse interactions occurred with blood thinners such as warfarin and antiplatelet drugs such as aspirin, the survey found.

“Physicians and pharmacists need to ask older patients about all the medications they use -- prescription and nonprescription -- and patients need to be prepared to share this information. This is especially important in patients who see multiple providers and patients that fill at multiple pharmacies,” Qato said.