Follow all directions on your prescription label. Do not take  isoniazid in larger or smaller amounts or for longer than recommended.
Take isoniazid on an empty stomach, at least 1 hour before or 2 hours after a meal.
Use this medicine for the full prescribed length of time. Your symptoms may improve before the infection is completely cleared. Skipping doses may also increase your risk of further infection that is resistant to antibiotics. Isoniazid will not treat a viral infection such as the flu or a common cold.
Your liver function may need to be checked every month while you are taking this medicine.
Your doctor may have you take extra vitamin B6 while you are taking isoniazid. Take only the amount of vitamin B6 that your doctor has prescribed.
Store at room temperature away from moisture, heat, and light. Keep the bottle tightly closed when not in use.
 Detailed Isoniazid dosage information
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What happens if I miss a dose?
Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.
Overdose symptoms may include vomiting, severe dizziness or drowsiness, slurred speech, blurred vision, hallucinations, trouble breathing, increased thirst, increased urination, fruity breath odor, or loss of consciousness.
