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Isoniazid

Brand names: INH

Isoniazid treats active and latent tuberculosis.

Brand namesINH
Type of medicineTB medicine
Prescription?Prescription
ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.

Overview

Vitamin B6 is often given with it to prevent nerve problems.

What it's used for

  • Active TB (with other medicines)
  • Latent TB

How to take it

  • Take it on an empty stomach once a day (or as scheduled).
  • Avoid alcohol.

Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.

Side effects

Common side effects

  • Nausea
  • Tingling in hands or feet
Call your provider todayYellow skin or eyes, dark urine, or pain in the upper right belly
Call your provider todayLoss of appetite, tiredness, or nausea (early liver injury)

Warnings

  • Boxed warning: severe liver injury, more likely with age and alcohol.

Other medicines, foods, and alcohol

  • It raises phenytoin and some other levels.
  • Acetaminophen may add to liver risk.

Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.

Pregnancy and breastfeeding

Used in pregnancy with vitamin B6.

Missed doses, overdose, and storage

If you miss a dose

Take it as soon as you remember, unless it's almost time for your next dose. Then skip the missed dose. Don't take two doses at once.

If someone takes too much

Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.

Storing it

Store at room temperature, away from heat and moisture (not in the bathroom), and out of reach of children and pets.

Conditions it's used for

Sources

Last updated 2026-11-13.