How long do antibiotics take to work?

There is no easy answer to this question. Most oral antibiotics are taken for 7 to 14 days, but some antibiotics, like fosfomycin (Monurol) -- used for a urinary tract infection (UTI) -- are given as one single dose and work fast. Others, such as tetracycline for acne, may need to be used for several months.

You should always complete the full course of your antibiotic, even if you feel better and it seems like you don't need your antibiotic anymore. If you stop your treatment early, your infection may return quickly and you may develop resistance to the antibiotic you were using previously. Your antibiotic may not work as well the next time you use it.