Norfloxacin usual adult dose: 400 mg twice daily (every 12 hours), typically taken on an empty stomach with water.

But the exact course depends on the infection and local guideline:

Do not self-start it for loose stools or urinary burning. Norfloxacin is a fluoroquinolone with risks including tendon injury, nerve symptoms, mood/CNS effects, and QT prolongation. It is generally reserved when safer antibiotic options are unsuitable. Avoid taking it with antacids, iron, calcium, zinc, or dairy close to the dose because absorption falls.

Please tell me the condition, age, pregnancy status, and kidney disease history, or use the dose exactly written by your clinician. The older FDA Noroxin label lists these regimens.