Isoniazid: What It Is and How It Works

Isoniazid is a drug that fights tuberculosis (TB). It attacks the bacteria that cause TB and helps stop the infection from spreading. Doctors usually give it as part of a combination treatment, so the bacteria don’t become resistant. If you’ve been told to take isoniazid, you’re likely on a plan that will last several months. The goal is simple – clear the infection and keep you from getting sick again.

Dosage and How to Take Isoniazid

The usual adult dose is 300 mg once a day, taken on an empty stomach. Some doctors may suggest a lower dose if you have liver problems or are pregnant. Children get a weight‑based dose, usually 10‑15 mg per kilogram of body weight each day. Take the pill with a full glass of water, and try to avoid dairy products an hour before or after you swallow it. Milk can lower how much of the drug your body absorbs.

Stick to the schedule your doctor gave you. Skipping doses can let the TB bacteria grow back and become harder to kill. If you miss a dose, take it as soon as you remember, unless it’s almost time for the next one – then just skip the missed dose. Don’t double up.

Side Effects and Safety Tips

Most people handle isoniazid without big problems, but you should know the common side effects. The drug can cause nausea, loss of appetite, or a mild rash. More serious issues involve the liver – you might feel tired, get yellow skin or eyes, or notice dark urine. If any of those happen, call your doctor right away.

Because liver damage is a real risk, doctors often order a blood test before you start and then every few months while you’re on the medication. You can help protect your liver by avoiding alcohol and limiting other medicines that strain the liver, like acetaminophen.

Another rare side effect is a change in your nerves, which can make your hands or feet feel tingly. This happens when your body runs low on vitamin B6. Your doctor may prescribe a small B6 supplement to prevent that problem.

When it comes to buying isoniazid, only use a licensed pharmacy. Look for a site that asks for a valid prescription and shows clear contact information. Beware of offers that sound too good to be true – cheap pills from unknown sources may be fake or unsafe. If you need help finding a reputable online pharmacy, check with your doctor or a local health authority.

Finally, keep all your follow‑up appointments. Your doctor will track how the infection is responding and adjust the treatment if needed. Completing the full course, even if you feel better early on, is the best way to finish the job and avoid a resistant TB strain.

In short, isoniazid is a key player in TB treatment. Take it exactly as prescribed, watch for side effects, and use a trustworthy pharmacy. With those steps, you give yourself the best chance for a full recovery.