Isoniazid & Nutrient Depletion
Also searched as Laniazid, INH, Nydrazid. What the clinical evidence reports, what it may mean, and what to discuss with your pharmacist.
Isoniazid has been associated with depletion of NIACIN and VITAMIN B6. This does not mean a deficiency will occur — it means these are worth knowing about and, if you take Isoniazid long-term, worth raising with your pharmacist or healthcare provider.
Take more than one medication? Open the checker with Isoniazid pre-loaded and add the rest to see overlapping nutrient signals.
Reported nutrient depletions with Isoniazid
Each record below is shown as published in our licensed clinical database, with its evidence rating and citations. Expand a section for food sources and talking points.
NIACIN
Moderate DepletionISONIAZID
Isoniazid can cause a deficiency of pyridoxine, which is needed for conversion of tryptophan to niacin, resulting in a secondary niacin deficiency. Isoniazid also has structural similarities to niacin and might interfere with niacin's conversion to nicotinamide adenine dinucleotide (NAD). Pellagra can occur in people taking isoniazid chronically, especially if dietary niacin intake is low. It can be prevented or reversed with niacin or niacinamide supplements.
Niacin is a B vitamin your body uses for energy production and keeping your skin, nerves, and digestive system healthy. Isoniazid can chip away at niacin levels through two routes: it depletes pyridoxine (vitamin B6), which your body normally uses to convert the amino acid tryptophan into niacin, and it may also interfere with how niacin is activated into its working form in the body. Because this is rated as moderate depletion, long-term users, especially those with low dietary niacin intake, have a real reason to ask their doctor or pharmacist whether monitoring or supplementation makes sense for them.
What Vitamin B3 (niacin) does & food sources
Niacin supports energy metabolism, skin health, and nervous system function.
Common food sources:
- Poultry, beef, and fish
- Peanuts and legumes
- Fortified grains
HelloPharmacist pharmacist-reviewed education — separate from the licensed record above.
What to discuss with your clinician
Deficiency is rare in a typical diet. Discuss with your provider before using niacin as a supplement — at pharmacologic doses it behaves like a medication.
HelloPharmacist pharmacist-reviewed education — separate from the licensed record above.
Supplement considerations
High-dose niacin causes flushing and can affect the liver, blood sugar, and uric acid — it is not a casual supplement.
Do not start or stop medications or supplements without professional guidance — supplements can interact with prescription medications.
HelloPharmacist pharmacist-reviewed education — separate from the licensed record above.
Caution: Treat high-dose niacin as a medication decision, not a nutrition one.
Learn more about this nutrient: Niacin — uses, safety & interactions
References (6)
- Shils ME, Olson JA, Shike M, Ross AC, eds. Modern Nutrition in Health and Disease. 9th ed. Baltimore, MD: Williams & Wilkins, 1999.
- Ishii N, Nishihara Y. Pellagra encephalopathy among tuberculous patients: its relation to isoniazid therapy. J Neurol Neurosurg Psychiatry 1985;48:628-34. PubMed
- Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline (2000). Washington, DC: National Academy Press, 2000. Available at: http://b
- Darvay A, Basarab T, McGregor JM, Russell-Jones R. Isoniazid induced pellagra despite pyridoxine supplementation. Clin Exp Dermatol 1999;24:167-9. PubMed
- Stratigos JD, Katsambas A. Pellagra: a still existing disease. Br J Dermatol 1977;96:99-106. PubMed
- Bender DA, Russell-Jones R. Isoniazid-induced pellagra despite vitamin B6 supplementation (letter). Lancet 1979;2:1125-6. PubMed
VITAMIN B6
Moderate DepletionISONIAZID
Isoniazid interacts with vitamin B6 to form an inactive hydrazine, which inhibits pyridoxal kinase and increases vitamin B6 excretion in the urine. This depletes body stores of vitamin B6 and can lead to peripheral neuritis. It is rare in people receiving up to 5 mg/kg daily isoniazid. With higher doses of isoniazid, consider vitamin B6 supplements, 40-250 mg daily, especially in people with a history of seizures, and in those with other risk factors for neuropathies, including malnutrition, uremia, diabetes, alcoholism, or liver disease. For information on foods that are rich in vitamin B6, see our chart.
Isoniazid is a tuberculosis antibiotic that has a well-known chemical interaction with vitamin B6, the nutrient your nerves and brain depend on to work properly. The drug latches onto B6 in the body, rendering it inactive and causing more of it to spill out through the urine, which can gradually drain your stores over time. This is rated a moderate concern, meaning deficiency does not happen to everyone but is real enough that long-term users, especially those on higher doses or with conditions like diabetes, should ask their doctor or pharmacist whether a B6 supplement makes sense for them.
What Vitamin B6 does & food sources
Vitamin B6 is involved in protein metabolism, neurotransmitter production, and red blood cell formation.
Common food sources:
- Poultry and fish
- Potatoes and starchy vegetables
- Bananas
- Fortified cereals
HelloPharmacist pharmacist-reviewed education — separate from the licensed record above.
What to discuss with your clinician
With some medications (for example, isoniazid), B6 is intentionally co-prescribed — follow your prescriber's plan. Otherwise, ask whether testing or supplementation is appropriate if you have symptoms like numbness or tingling.
HelloPharmacist pharmacist-reviewed education — separate from the licensed record above.
Supplement considerations
Paradoxically, long-term high-dose B6 can itself cause nerve symptoms — this is a nutrient where more is definitely not better.
Do not start or stop medications or supplements without professional guidance — supplements can interact with prescription medications.
HelloPharmacist pharmacist-reviewed education — separate from the licensed record above.
Caution: Avoid high-dose B6 without medical guidance; sustained high intakes can cause neuropathy.
Learn more about this nutrient: Vitamin B6 — uses, safety & interactions
References (5)
- Shils ME, Olson JA, Shike M, Ross AC, eds. Modern Nutrition in Health and Disease. 9th ed. Baltimore, MD: Williams & Wilkins, 1999.
- Matsui MS, Rozovski SJ. Drug-nutrient interaction. Clin Ther 1982;4:423-40.
- Bass JB, Farer LS, Hopewell PC, et al. Treatment of tuberculosis and tuberculosis infection in adults and children. Am J Respir Crit Care Med 1994;149:1359-74..
- Pellock JM, Howell J, Kendig EI Jr, et al. Pyridoxine deficiency in children treated with isoniazid. Chest 1985;87:658-61. PubMed
- Snider DE Jr. Pyridoxine supplementation during isoniazid therapy. Tubercle 1980;61:191-6. PubMed
This tool is educational and is not a substitute for professional medical advice. An association is not a diagnosis and does not mean a deficiency will occur. Always talk to your pharmacist or healthcare provider before starting, stopping, or changing any medication or supplement.
Disclaimer: This checker finds which nutrients might be depleted by prescription or over-the-counter medications. Each nutrient depletion issue is rated based on clinical significance. Use your own professional judgment prior to making clinical decisions.© 2026 Therapeutic Research Center Licensed records refresh weekly · last updated July 3, 2026.
More about Isoniazid
What drug-induced nutrient depletion means
Some medications can, over time, lower the levels of certain vitamins, minerals, or other nutrients — through reduced absorption, increased loss, or changes in how the body uses them.
Association is not deficiency
An entry here means a depletion has been reported or studied — not that it happens to everyone, or that you are deficient. Dose, duration, diet, and your own health all matter.
Evidence varies by pair
Some drug–nutrient links (like metformin and vitamin B12) are well studied; others rest on limited or preliminary research. Each entry shows the evidence rating from our licensed clinical database.
When to ask about labs
If you take an associated medication long-term, ask your healthcare provider whether monitoring is appropriate for you. Not everyone needs testing — your provider can weigh your dose, duration, and symptoms.
Don't self-supplement blindly
Supplements are not risk-free: some can interact with medications, and some (like potassium or magnesium) can be risky with kidney disease. Talk to your pharmacist before adding anything.
Never stop a medication over this
These medications are prescribed for good reasons, and the benefit usually far outweighs a manageable nutrient consideration. Any change belongs in a conversation with your prescriber.
Food first, usually
For many nutrients, a varied diet covers the gap. Each entry lists common food sources; a supplement is a decision to make with your pharmacist or provider, not a default.
Isoniazid & nutrients: FAQs
Does Isoniazid deplete NIACIN?
Should I take a supplement because I take Isoniazid?
Should I stop taking Isoniazid?
Where does this information come from?
Questions about Isoniazid and your nutrition?
Ask a licensed pharmacist — free, no appointment needed.
Sources & How We Checked
Nutrient depletion records for Isoniazid are evidence-graded and sourced from the Natural Medicines database, and are displayed as published with their citations.
- Natural Medicines (Therapeutic Research Center) — Evidence-graded clinical reference for drug-induced nutrient depletions, supplements, and interactions — the basis for this page.
- MedlinePlus, U.S. National Library of Medicine — NIH consumer drug information, used for medication overviews across the site.
Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.