Isoniazid (often called INH) is one of the oldest and most effective drugs for tuberculosis. It kills TB bacteria and is used both for active disease (with other TB drugs) and for latent TB infection to prevent disease later. Sounds simple, but the drug can affect your liver and nerves, so a few rules make treatment much safer.
For latent TB, the usual dose for adults is 300 mg once daily for 6–9 months. Some programs use higher-dose intermittent schedules (twice weekly) under direct observation. For active TB, isoniazid is one part of a multi-drug regimen and doctors adjust doses by weight—typical is about 5 mg/kg up to 300 mg daily.
Take isoniazid on an empty stomach (one hour before or two hours after a meal) for best absorption. If stomach upset is a problem, it’s okay to take it with food, but effectiveness may drop a bit. Try to take the medicine at the same time each day to build a routine.
Always follow the exact plan your clinician gives you. Stopping early or missing doses can let TB come back and makes resistant TB more likely.
The biggest concern with INH is liver injury. Before starting, doctors usually check baseline liver tests. If you have existing liver disease, drink alcohol regularly, or are over 35, your provider will monitor labs more closely—often monthly. Watch for yellowing of skin or eyes, dark urine, severe nausea, or persistent abdominal pain. Report these quickly.
INH can cause peripheral neuropathy (tingling or numbness in hands or feet). That’s preventable: take pyridoxine (vitamin B6) 25–50 mg daily while on INH, especially if you’re pregnant, diabetic, pregnant, underweight, alcoholic, or have HIV.
Other side effects: rash, fever, and rare immune reactions. Very rarely INH can cause mood changes or memory trouble—tell your clinician if you notice new confusion or depression.
Isoniazid interacts with some medicines that are broken down by the liver. Drugs like phenytoin, carbamazepine, and warfarin may need dose checks while you’re on INH. Tell your clinician about all meds, supplements, and herbal products you take.
Practical tips: avoid booze while on INH, carry a treatment card if you travel, and set reminders so you don’t miss doses. If you’re pregnant or breastfeeding, TB treatment is usually still recommended—talk it over with your doctor rather than stopping on your own.
If you have questions about purchasing medications online or finding a pharmacy, pick services with clear contact info, valid prescriptions, and verified reviews. Your health matters—treat TB seriously and follow monitoring steps so treatment works and stays safe.
Curious about buying Isoniazid online? Learn legit ways to get this TB medication, what to watch out for, and how to stay safe and legal.