Isoniazid
$0.38
Isoniazid is a key antibiotic used to treat and prevent tuberculosis, usually alongside other TB medicines.
Drug Information
5 reviews for Isoniazid
Isoniazid (also called INH) is one of the main medicines used to treat tuberculosis (TB), a serious lung infection that can also affect other parts of the body.
For active TB it is always taken together with other TB medicines. On its own, it is used to stop "sleeping" (latent) TB from turning into active disease.
What is it used for?
- Active tuberculosis, together with other TB medicines
- Latent (sleeping) TB infection, to prevent it becoming active
How does it work?
Isoniazid stops TB bacteria from building the special waxy wall that protects them. Without it, the bacteria die.
This information is written in simple words to help you understand this product. It does not replace advice from your doctor or pharmacist.
Read these points before you start. If any of them apply to you, talk to your doctor or pharmacist first.
- Do not take it if you have ever had an allergic reaction to this antibiotic or to a similar one.
- Antibiotics only work on infections caused by bacteria. They do not help colds, flu or most sore throats, which are caused by viruses.
- Take the whole course your doctor gives you, even if you feel better after a few days. Stopping early can let the infection come back and make germs harder to treat in the future.
- Tell your doctor if you are pregnant, trying for a baby or breastfeeding.
- Never share your antibiotics or keep leftovers for another time.
- It can harm the liver. Do not drink alcohol, and go to all your blood tests. The risk is higher if you are over 35, drink alcohol, or have liver disease.
- It can lower vitamin B6 and cause nerve damage. Your doctor may prescribe a vitamin B6 (pyridoxine) tablet to take with it.
- Tell your doctor if you have epilepsy, kidney problems, diabetes, HIV or a history of nerve problems.
- It can raise the levels of phenytoin and carbamazepine (seizure medicines).
- Tell your doctor or pharmacist about every other medicine, vitamin or herbal product you use.
- Keep this product out of the reach and sight of children.
Like all medicines, Isoniazid can cause side effects, but not everybody gets them.
Common side effects
- Feeling sick (nausea) or being sick
- Diarrhoea or loose stools
- Stomach ache or indigestion
- Numbness or tingling in the hands or feet (can be prevented with vitamin B6)
These are usually mild and often get better as your body gets used to it. Tell your doctor if they bother you or do not go away.
Stop using it and get medical help straight away if you notice:
- Severe diarrhoea that is watery or has blood in it, even up to 2 months after you finish the medicine
- Signs of an allergic reaction, such as a rash, swelling of the face, lips or tongue, wheezing or trouble breathing
- A skin rash that blisters or peels, with fever and sore mouth or eyes
- Yellowing of the skin or eyes, dark urine, pale stools, or loss of appetite with tiredness and sickness (liver problems)
- Blurred vision or eye pain
This is not a complete list. If you notice anything unusual, ask your doctor or pharmacist.
- Take it once a day, at the same time each day.
- Take it on an empty stomach, 1 hour before or 2 hours after a meal, with a glass of water.
- The usual adult dose is 300 mg once a day (or 5 mg per kilogram of body weight).
- Treatment usually lasts 6 to 9 months. Do not stop early, even when you feel well, or TB can come back and become harder to treat.
If you miss a dose: Take it as soon as you remember. If it is nearly time for your next dose, skip the missed one and carry on as normal. Never take two doses at once to make up.
If you use too much: Contact your doctor, a poison control centre or your local emergency number straight away, even if you feel fine. Take the pack with you.
How to store it: Keep it in its original pack at room temperature (below 25°C / 77°F), away from heat, damp and direct sunlight. Do not use it after the expiry date.
- QWhy do I need to take Isoniazid for so long?
- A
TB bacteria grow very slowly and are hard to kill. Months of treatment are needed to get rid of all of them.
- QWhy did my doctor give me vitamin B6 with Isoniazid?
- A
Isoniazid can use up vitamin B6 and cause tingling in the hands and feet. The vitamin helps prevent this.
- QCan I drink alcohol while taking Isoniazid?
- A
No. Alcohol raises the chance of liver damage.
- QIs TB still contagious once I start Isoniazid?
- A
Once you have been on the right TB medicines for about 2 weeks, most people are much less contagious. Your doctor will tell you when it is safe to be around others.

Chioma Hughes –
This was my second order from the site. The team kept me updated on the status of my Isoniazid order. The steps at checkout were easy to follow. It was cheaper than my usual place, and the service was just as good.
Fatima Tanaka –
It was dispatched fast and reached me soon after. I had no trouble at checkout, which is not always the case on other sites. Solid experience, nothing to complain about.
Isabelle Bekele –
I liked that the site did not make things complicated. The cost was clearly shown before I paid, so no nasty surprises. The Isoniazid I ordered showed up right when they said it would. A good experience from start to finish.
Ishaan Hoffmann –
I got my Isoniazid here and the experience was easy. The right item came, and the label matched my order.
Isaac Ahmed –
The support staff were quick to respond and easy to deal with. Everything with my Isoniazid was in order when I opened the box. For the price, I could not ask for more.