Anti-TB medicinePrescription only
Isoniazid
Tablet
Quick Summary
Isoniazid kills TB bacteria. It's used with other medicines for active TB and alone for preventing TB in some people.
Tuberculosis
TB prevention
Medical Uses
Tuberculosis: As part of combination treatment.
TB prevention: For people at high risk, such as close contacts.
How it's taken
Taken daily on an empty stomach. Vitamin B6 (pyridoxine) is often given to prevent nerve problems.
Your doctor decides the right dose for you and how long to take it.
Your doctor decides the right dose for you. Follow their instructions and the label.
Common Side Effects
Tingling hands or feet
Nerve effects; B6 helps.
Liver problems
Jaundice or dark urine.
Nausea
Sometimes.
Interactions
Phenytoin and carbamazepine
Levels may rise.
Alcohol
Increases liver risk.
Critical Warnings
Liver damage
Seek help for yellow eyes, dark urine, vomiting or tummy pain.
Alcohol
Avoid during treatment.
Sources and further reading
Last updated 21 October 2026. For more detail, see these trusted health organisations.
- Isoniazid: drug information(opens in a new tab) · MedlinePlus, US National Library of Medicine