The company's McNeil Consumer Healthcare Division says the change affects Extra Strength Tylenol sold in the U.S.
Labels on the bottles will now list the maximum daily dose as six pills, or a total of 3,000 milligrams, down from eight pills a day or 4,000 milligrams.
Acetaminophen is the active ingredient in Tylenol and numerous other prescription and nonprescription pain relievers, including Percocet, Vicodin, NyQuil and some Sudafed. People taking multiple products at once don't always realize how much acetaminophen they are ingesting.
Excessive use of acetaminophen can cause liver damage and even fatal overdoses.