The risk associated with low-dose norfloxacin and ciprofloxacin in leptospirosis. Low-dose norfloxacin and ciprofloxacin reduced survival rate. Low-dose norfloxacin increased bacterial loads in target organs. Low-dose norfloxacin aggravated tissue injury of target organs. Low-dose norfloxacin delayed induction of IL-1β and TNF-α in tissues.