Dose is set by your doctor as part of TB treatment, usually 5 mg per kg (about 300 mg for adults) once a day on an empty stomach. Vitamin B6 (pyridoxine) is often given with it. Never stop TB treatment early.
Your doctor may give you a different dose. Children's doses depend on weight.
Stop taking it and see a doctor straight away if you notice:
Medicines that can react with this one.
Raises carbamazepine levels, and the combination raises the risk of liver damage.
Isoniazid raises phenytoin levels and can cause toxicity; levels should be checked.
Antacids reduce absorption; take isoniazid at least 1 hour before them.
Pyridoxine is usually given with isoniazid on purpose to prevent nerve damage; this is a helpful combination.
