['To assess the effect of adding an acetaminophen ingredient icon to acetaminophen medication labels on consumer decision making about concomitant use of acetaminophen medications to avoid overdose, which is associated with liver injury.', 'Parallel-group randomized study.', 'Consumer research facilities in Indianapolis, Baltimore, and Los Angeles.', 'A total of 517 adults (30% with limited health literacy) recruited at 3 consumer research sites.', 'Participants were randomized to a non-icon condition in which medications carried current labeling or an icon condition in which all acetaminophen medications were additionally marked with an icon.', 'Participants were presented with a medicine cabinet containing 12 diverse prescription and non-prescription medications, one-half containing acetaminophen, and made decisions about which medications were appropriate to take after an acetaminophen medication had already been taken. Outcome measures were errors in medication decisions and response time.', 'The icon reduced the odds of participants making medication-decision errors by 53% (CI 31%-68%), with effects evident across medication categories. The icon eliminated a trend for those with lower health literacy or less education to have a greater likelihood of making errors. The icon also reduced response times, indicating reduced cognitive load for decisions.'] Does an acetaminophen icon help reduce medication decision errors in an experimental setting?