Ciprofloxacin dosage for UTI. Adults: 250 mg every 12 hours for 7 to 14 days. Complicated infections require 500 mg every 12 hours. Children 1-17 years of age: 10–20 mg/kg (up to 750 mg) every 12 hours for 10–21 days. Cystitis (bladder infection) in women: The usual dosage is 250 mg every 12 hours for 3 days.