Acetaminophen overdoses can be very serious

Just because you can buy a medication without a prescription, doesn't mean it can't hurt you.

Almost 80,000 people wind up in a hospital emergency room each year because they took too much acetaminophen, the active ingredient in Tylenol.

"It's very safe up to just about 4,000mg a day," said Lisa Gill with Consumer Reports Best Buy Drugs. "As you start to creep over 4,000, you start to get into a very risky area, and it doesn't take a whole lot of extra acetaminophen to get you into the danger zone."

Gill says acetaminophen is now the most common cause of liver failure in this country.

You shouldn't drink alcohol if you're taking products with acetaminophen, and you need to be careful about other medications that contain the drug. That's a common way of overdosing.

"Acetaminophen shows up in more than 600 products, both products that you get without a prescription, just on the pharmacy shelf, and products that you get with a prescription," Gill told me.

It's especially common in combination cough-and-cold and allergy relief medications.

More Info: Consumer Reports Special Report: The Dangers of Painkillers