Researchers at Dartmouth University surveyed almost 300 pharmacies in the Bronx, New York, where 44 percent of the population speaks Spanish.
About three quarters of pharmacies there provide medicine labels in Spanish to customers who need them. Most of those pharmacies use computers to translate labels.
According to the researchers' findings, half of the labels contained serious mistakes including incomplete translations and crucial spelling or grammatical errors.
In one case, a Spanish-speaking man who was supposed to take his two blood pressure medications once a day took 11 pills of each instead because the word "once" in English means "11" in Spanish.
Doctors hope computer translation programs will be improved, and stress that medical professionals should always check the work of computers.