antibiotics are used to treat simple cases of urinary tract infections. resistance to antibiotics is increasing. people who have complicated urinary tract infections sometimes have to take antibiotics for a longer time, or might take antibiotics intravenously (through a vein). if symptoms have not improved in two or three days, the person will need further tests. in women, urinary tract infections are the most common form of bacterial infection. ten percent of women develop urinary tract infections each year.