By Ian Schwartz

Phoenix, AZ (KPHO) -- Getting older sometimes means you have to take more pills than you used to, but they could be putting you at risk on the road and you don't even know it.

AAA did a study that came back with some pretty surprising results.

They found a lot of older drivers took medication and continued to drive. This could be anything from blood thinners, arthritis medications or heart medications.

While that's not terribly surprising, the amount of drivers taking medications that could impair their driving was.

About 20 percent of older adults are doing that and they don't even know it, according to the AAA study. Drivers are taking drugs that could pose a risk or mixing two harmless drugs that could cause a bad reaction.

And this isn't a small group of people on the roads. AAA says there are more than 40 million drivers on the road who are 65 and older, and the number baby boomers is expected to grow substantially in the next decade.

“Many older drivers are using medications that they don’t know should be avoided while operating a vehicle,” said Michelle Donati, spokeswoman for AAA Arizona. “While taking medications can affect all of us, older drivers are more vulnerable and it is important for them to know the side effects associated with the medications they are taking.”

Dontati said it is always a good idea to double check with your doctor about what medication you are on and how it could impact your safety and the safety of others while you are on the road.

Don't always assume they will tell you. That same study found around 60 percent of people surveyed said their doctor never told them about how prescriptions could impact their driving.

The study also found than people often were getting prescribed different medications from different doctors and something the two were not communicating properly.