Taking too many pills at once is not the only way to overdose. Taking twice the recommended daily dosage of acetaminophen for several days led to hospitalization and death, according to a study published online in the British Journal of Clinical Pharmacology.

The Food and Drug Administration recommends consuming no more than 4,000 milligrams of acetaminophen per day. Acetaminophen is the primary ingredient in Tylenol, NyQuil, Theraflu, and other pain relievers.

In a study of 600 patients hospitalized for liver problems caused by acetaminophen, “staggered overdoses” -- in which the daily dose is exceeded over a period of days -- were more deadly than single overdoses, when too many pills are taken at once.

About one-fourth of the patients had taken staggered overdoses (e.g., 24,000 mg over several days), and 37 percent of these patients died. Compare this to a 28 percent mortality rate for those who had taken a single overdose (e.g., 27,000 mg at once). Patients with staggered overdoses were also more likely to have liver and brain problems, require dialysis and help breathing.

People taking acetaminophen should stay within the daily limits of drug, or take less of it, said study researcher Kenneth Simpson of the University of Edinburgh.

Acetaminophen is the leading cause of liver failure in the U.S. each year.

Earlier this year, Johnson & Johnson said it would be lowering the recommended maximum daily dose of its Extra Strength Tylenol pain relievers from 4,000 to 3,000 milligrams.