In fasted mice, plasma glucose levels were reduced by intraperitoneal administration of enoxacin, lomefloxacin, or gatifloxacin (50 mg/kg). A lower dose of these fluoroquinolones (5 mg/kg) also reduced the plasma glucose (PG) levels in glucose-loaded mice. Ciprofloxacin and levofloxacin did not reduce these levels in either fasted or glucose-loaded mice. These results suggest that each fluoroquinolone has an individual hypoglycemic action, and fluoroquinolone administration after meals might reduce PG levels at lower doses.