Vitamin B6 Deficiency: Symptoms, Causes, and Recovery

Vitamin B6 (pyridoxine) is a quiet workhorse: in its active form it powers more than 150 enzyme reactions, from building the brain chemicals that steady your mood to assembling the hemoglobin that carries oxygen in your blood. When it runs short, the trouble shows up in a scattered, easily-missed pattern — a greasy, scaly rash around the nose and eyebrows, cracked corners of the mouth, a sore red tongue, tingling or burning in the hands and feet, low mood and foggy thinking, a mild anemia, and — in young infants — seizures. Frank deficiency from diet alone is uncommon in healthy adults, because B6 is widespread in food. Far more often a low level is driven by something else: heavy alcohol use, certain medications (the tuberculosis drug isoniazid, the arthritis drug penicillamine, and the Parkinson's drug levodopa are the classic culprits), kidney disease, pregnancy, or the inflammation of a long-running illness. The reassuring part is that B6 status is measurable with a simple blood test, and the deficiency usually corrects readily — with a better diet and, where needed, a sensible supplement. This hub explains what the deficiency is, why one vitamin shortage causes such different symptoms, what causes it, who is most at risk, how it is diagnosed, and exactly how it is corrected — with deep-dive pages for each major symptom group.

Symptom Deep-Dive Pages

Table of Contents

1. Symptom Deep-Dive Pages
2. What Is Vitamin B6 Deficiency?
3. Why One Shortage Causes So Many Symptoms
4. Common Causes of Low Vitamin B6
5. Who Is Most at Risk
6. How Vitamin B6 Deficiency Is Diagnosed
7. How Low Vitamin B6 Is Corrected
8. When to Seek Care / Red Flags
9. Key Research Papers
10. Connections
11. Featured Videos

What Is Vitamin B6 Deficiency?

Vitamin B6 is the umbrella name for a small family of related compounds — pyridoxine (the form usually found in supplements and plant foods), pyridoxal, and pyridoxamine. Inside the body, all of them are converted into one active form, pyridoxal 5′-phosphate (PLP), which is the chemical that actually does the work. Vitamin B6 deficiency means the body does not have enough PLP to run the enzyme reactions that depend on it. Doctors most often measure it as the level of PLP in the blood; a plasma PLP below about 20 nmol/L is generally considered deficient, and the range between roughly 20 and 30 nmol/L is regarded as marginal or insufficient.

It helps to think of the deficiency as a spectrum rather than an on/off switch:

• Marginal (insufficient) status — PLP is low-normal, often with no obvious symptoms at all. This is surprisingly common. National survey data (NHANES) found that a meaningful fraction of U.S. adults — including many who do not take a supplement, smokers, and women using oral contraceptives — sit below the adequacy cut-off even though they would never call themselves "deficient."
• Mild-to-moderate deficiency — now symptoms begin to appear, and they are the kind that are easy to attribute to something else: a flaky, greasy rash on the face and scalp (seborrheic dermatitis), cracked corners of the mouth and a sore, smooth tongue, low mood or irritability, and tingling in the hands or feet.
• Severe deficiency — uncommon today but well-documented historically and in specific settings (alcohol-use disorder, certain medications, malabsorption). It can produce a clear peripheral neuropathy, a microcytic anemia, confusion, and, in infants, seizures.

Two facts are worth holding together. First, true dietary deficiency in an otherwise healthy adult is uncommon, because B6 is plentiful in ordinary foods and the recommended intake (1.3–1.7 mg/day for most adults) is not hard to reach. Second, B6 deficiency rarely travels alone. It is so often part of a broader picture — poor diet, heavy alcohol use, malabsorption, or a B-vitamin shortfall across the board (the deficiency frequently coexists with low folate and low B12) — that finding it should prompt a look for the company it keeps.

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Why One Shortage Causes So Many Symptoms

The puzzle of B6 deficiency is how a single vitamin shortage can cause complaints as different as a facial rash, burning feet, low mood, and anemia. The answer is that PLP is not a specialist — it is a master coenzyme, a helper molecule that more than 150 different enzymes physically clamp onto in order to function. Take away the helper and dozens of unrelated-looking reactions slow down at once.

Here is the core idea in everyday language. Most of the body's chemistry that involves amino acids — the building blocks of protein — runs through PLP-dependent enzymes. That single fact ties together the scattered symptoms:

• Brain chemistry. PLP is the final-step enzyme cofactor that builds several key neurotransmitters from amino acids: serotonin (from tryptophan), dopamine and noradrenaline (from tyrosine), and GABA, the brain's main calming signal (from glutamate). When PLP runs low, the brain's supply of these messengers can fall — the mechanistic reason low B6 is linked with low mood, irritability, and, in extreme infant deficiency, seizures (because too little calming GABA leaves the brain over-excitable). Deep dive: Depression & Confusion and Anemia & Seizures. See also B6 and Neurotransmitter Synthesis.
• Blood and oxygen. The very first step of building heme — the iron-containing core of hemoglobin that carries oxygen — is run by a PLP-dependent enzyme (ALAS2) inside red-cell precursors. Without enough PLP, immature red cells cannot finish hemoglobin and iron piles up unused, producing a small, pale (microcytic) sideroblastic anemia. Deep dive: Anemia & Seizures.
• Skin and lining tissues. Rapidly renewing tissues — the skin, the lining of the mouth, the tongue — depend on smooth amino-acid and one-carbon metabolism to keep replacing cells. When that metabolism stutters, the result is the classic seborrheic dermatitis, cracked lips (cheilosis), and a sore, inflamed tongue (glossitis). Deep dive: Skin Rashes & Cracked Lips.
• Nerves. Peripheral nerves rely on steady metabolic support, and B6 is involved in the sphingolipid chemistry that maintains the myelin sheath. Deficiency can produce a "stocking-and-glove" peripheral neuropathy — tingling, burning, or numbness that starts in the feet and hands. (Curiously, as the deep-dive explains, both too little and too much B6 damage nerves.) Deep dive: Nerve Symptoms.
• Homocysteine. PLP is the cofactor for the transsulfuration enzymes that clear the amino acid homocysteine. When B6 (often alongside folate and B12) runs low, homocysteine can rise — a measurable marker that ties the B vitamins together. See B6 and Homocysteine and the Homocysteine test.

This is the unifying theme to carry into the symptom pages: there is nothing mysterious about B6 deficiency producing a scattershot of problems. One coenzyme sits behind protein chemistry across the whole body, so one shortage is felt in many places at once.

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Common Causes of Low Vitamin B6

Because dietary B6 is widespread, an isolated deficiency from food alone is unusual in a healthy person. In practice, a low level is far more often secondary — caused or worsened by alcohol, medications, illness, or increased need. Here are the causes worth knowing.

• Heavy alcohol use. One of the most common and important causes. Alcohol harms B6 status from several directions at once: people who drink heavily often eat poorly, alcohol impairs the conversion of B6 into active PLP, and a breakdown product of alcohol (acetaldehyde) actively displaces PLP from its carrier and speeds its destruction. The result is that low B6 is common in alcohol-use disorder, frequently alongside low folate, thiamine (B1), and magnesium.
• Isoniazid (INH). The cornerstone tuberculosis drug isoniazid chemically binds to PLP and B6, inactivating the vitamin and increasing its loss in the urine. This is so predictable that doctors routinely co-prescribe pyridoxine (typically 25–50 mg/day) with isoniazid specifically to prevent the peripheral neuropathy it would otherwise cause. Related drugs (cycloserine, hydralazine) act similarly.
• Penicillamine. Used for rheumatoid arthritis, Wilson's disease, and cystinuria, penicillamine reacts with PLP and inactivates it, and supplemental B6 is often given alongside it.
• Levodopa (without carbidopa). Vitamin B6 accelerates the breakdown of levodopa before it reaches the brain, reducing its effect in Parkinson's disease — the classic reason older Parkinson's patients were once warned off B6. Modern combination pills (levodopa with carbidopa) block this interaction, so the concern largely applies to plain levodopa. It is a genuine, repeatedly documented drug–nutrient interaction worth knowing in both directions.
• Kidney disease and dialysis. Chronic kidney disease lowers B6 status, and hemodialysis removes water-soluble vitamins from the blood, so people on dialysis are routinely given B-vitamin supplements that include B6.
• Malabsorption. Conditions that damage the small intestine — celiac disease, inflammatory bowel disease, and bariatric (weight-loss) surgery — reduce absorption of B6 along with other nutrients, and B6 deficiency in these settings travels with iron, B12, and folate deficiencies.
• Chronic inflammation. A long-running inflammatory illness (rheumatoid arthritis, inflammatory bowel disease, and others) lowers plasma PLP, partly by speeding up the vitamin's catabolism. Ulvik and colleagues showed that systemic inflammation increases breakdown of B6, which is why a low PLP in an inflamed patient can reflect the illness as much as true depletion.
• Increased need: pregnancy and breastfeeding. Requirements rise in pregnancy (1.9 mg/day) and lactation (2.0 mg/day) to supply the growing baby; plasma PLP naturally falls during pregnancy, and intake sometimes does not keep pace.
• Poor or restrictive diet. On its own this rarely causes severe deficiency in a healthy adult, but a chronically poor diet — in frailty, food insecurity, or eating disorders — lowers the reserve and makes any of the causes above bite harder. Older adults are particularly prone to marginal status.

A practical note: these causes often stack. An older adult who drinks regularly, eats little, and takes a medication that interferes with B6 can become deficient from the sum of several modest pushes in the same direction.

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Who Is Most at Risk

Some groups are far more likely to be low in B6 than the general population. If you recognize yourself here, it is reasonable to pay attention to intake and, if symptoms fit, to ask about testing.

• People with alcohol-use disorder — the single most common at-risk group, for all the reasons above. Low B6 typically appears here alongside low thiamine, folate, and magnesium.
• People taking B6-interfering medications — especially isoniazid for tuberculosis, penicillamine, cycloserine, and hydralazine. Pyridoxine is often deliberately co-prescribed with these.
• Older adults — marginal B6 status is common with aging, driven by lower intake, more medications, and more chronic inflammation. Survey data consistently show lower PLP in older age groups.
• Pregnant and breastfeeding women — higher requirements and a naturally falling plasma PLP during pregnancy.
• People with kidney disease, especially on dialysis — both the disease and the dialysis process lower B6.
• People with malabsorption — celiac disease, inflammatory bowel disease, and those who have had weight-loss surgery.
• People with chronic inflammatory conditions — rheumatoid arthritis and inflammatory bowel disease are associated with low plasma PLP.
• Newborns — a special case. Most infant B6-responsive seizures are not ordinary dietary deficiency but a rare inherited disorder (pyridoxine-dependent epilepsy), covered on the Anemia & Seizures page.

Notably, strict vegetarians and vegans are not at unusual risk of B6 deficiency the way they can be for B12 — B6 is abundant in plant foods such as chickpeas, potatoes, bananas, and fortified cereals. The vegan caution belongs to B12, not B6.

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How Vitamin B6 Deficiency Is Diagnosed

The reassuring part of this story is that B6 status can be measured directly. The standard test is a plasma pyridoxal 5′-phosphate (PLP) level — a blood test for the active form of the vitamin. As a guide, a plasma PLP below about 20 nmol/L is considered deficient and 20–30 nmol/L marginal, though exact cut-offs vary slightly between laboratories. It is a specialized test rather than part of a routine panel, so a doctor usually orders it when the clinical picture — the rash, the neuropathy, the anemia, or a high-risk situation such as isoniazid use — raises the question.

Because B6 deficiency so often travels with other problems, the work-up usually looks wider than a single number:

• A complete blood count (CBC). If anemia is present, the CBC shows whether the red cells are small and pale (microcytic), which would fit a B6-related sideroblastic anemia and point toward further testing. (For what the CBC measures, see the Complete Blood Count page.) Because microcytic anemia is far more often caused by iron deficiency, an iron panel is usually checked too.
• Homocysteine (and sometimes other markers). A raised homocysteine can accompany low B6 (and low folate or B12), and a low B6 status sometimes also lowers a related marker called cystathionine. These functional markers can support the diagnosis when the picture is unclear.
• Folate and vitamin B12. Because the B vitamins are commonly depleted together, folate and B12 are often measured alongside B6 so the whole pattern is seen at once.
• A look for the cause. Diagnosis is not finished at "B6 is low." The more useful question is why — a review of alcohol intake, medications (especially isoniazid), kidney function, gut/malabsorption history, and inflammatory illness usually reveals the driver, which is the thing that actually has to be fixed.

One nuance worth knowing: in someone with active inflammation, a low plasma PLP can partly reflect the illness redistributing and consuming the vitamin rather than pure dietary depletion — which is one reason results are interpreted alongside the whole clinical picture rather than in isolation.

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How Low Vitamin B6 Is Corrected

Treatment is matched to severity and, above all, to cause. The unifying principles are: raise B6 with food first where possible, supplement sensibly when needed, fix the underlying driver, and — importantly — do not overshoot, because too much B6 causes its own nerve problem.

• Mild cases — food first. When B6 is only modestly low and the cause is dietary, a richer diet both raises the level and supports overall health. B6 is plentiful in tuna and salmon, poultry, pork and beef, chickpeas and other legumes, potatoes and starchy vegetables, bananas, and fortified cereals. The recommended intake for most adults is modest — 1.3 mg/day, rising to 1.7 mg for older men and 1.5 mg for older women — and easily met by everyday meals. See the B6 food sources page for a fuller list and practical amounts.
• Moderate cases — oral supplementation. When food is not enough, oral pyridoxine corrects the deficiency reliably and quickly, since B6 is well absorbed. Typical replacement doses are in the range of a few milligrams up to perhaps 25–50 mg/day, used for a defined period and then stepped down to a maintenance level. The skin, mouth, mood, and anemia changes generally improve over days to a few weeks once levels are restored.
• Drug-related cases — co-prescription. When a medication is the cause, the answer is usually to give pyridoxine alongside it rather than to stop the drug. The classic example is isoniazid, where 25–50 mg/day of pyridoxine prevents neuropathy; penicillamine is handled the same way. (The levodopa interaction is the exception — here the goal is to avoid high-dose B6 with plain levodopa.)
• Treat the cause. Replacing B6 without addressing the reason it dropped simply resets the clock. That might mean reducing alcohol, adjusting nutrition in malabsorption, providing routine B-vitamin supplements in dialysis, or treating the inflammatory illness. Because B6 often runs low alongside folate and B12, doctors frequently correct the whole B-vitamin picture together.
• Critical caution — do not overdo it. This is the one rule that makes B6 different from most vitamins. Excess B6 — from large or long-term supplements, not from food — causes a sensory peripheral neuropathy of its own, with tingling, numbness, and unsteadiness. More is emphatically not better. Correct a deficiency to a normal level and stop; avoid open-ended high-dose B6. This is covered in detail on the Vitamin B6 Toxicity hub and the sensory neuropathy page.

For most people the outlook is excellent: once B6 is restored and the cause is handled, the rash, sore mouth, tingling, low mood, and mild anemia resolve, often within a few weeks.

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When to Seek Care / Red Flags

Most B6-deficiency symptoms are uncomfortable rather than dangerous, and a non-urgent appointment is the right step for a persistent facial rash, cracked lips, a sore tongue, low mood, or mild tingling — especially if you drink heavily, take isoniazid or penicillamine, have kidney or gut disease, or are pregnant. But certain situations deserve prompt or emergency attention:

• A seizure in a newborn or young infant — especially seizures that do not respond to standard anti-seizure medicines. This is a medical emergency and can be the presentation of a rare B6-responsive epilepsy that needs urgent, specific treatment. Seek emergency care immediately.
• Rapidly worsening or spreading numbness, weakness, or unsteadiness — significant or progressive nerve symptoms should be evaluated promptly, both to find the cause and because, paradoxically, they can be a sign of B6 excess from over-supplementation as well as deficiency.
• Symptoms of anemia that limit you — marked fatigue, breathlessness on exertion, a racing heart, or pallor warrant medical assessment to find and treat the cause.
• Confusion or a notable change in thinking — new confusion, especially in an older adult or someone with heavy alcohol use, should be assessed promptly rather than assumed to be "just" a vitamin issue.
• You are on isoniazid and develop tingling or numbness — tell your prescriber; this is the textbook B6-deficiency neuropathy and is both preventable and treatable with pyridoxine.

People at higher risk — those with alcohol-use disorder, on B6-interfering drugs, with kidney disease, or with malabsorption — should have a lower threshold for getting checked. When in doubt, a simple blood test and a review of medications and diet usually settle the question. For related conditions, see Peripheral Neuropathy, Anemia, Depression, and Epilepsy.

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Key Research Papers

1. Stach K, Stach W, Augoff K (2021). Vitamin B6 in Health and Disease. Nutrients;13(9):3229. — DOI: 10.3390/nu13093229
2. Ueland PM, Ulvik A, Rios-Avila L, Midttun Ø, Gregory JF (2015). Direct and Functional Biomarkers of Vitamin B6 Status. Annual Review of Nutrition;35:33-70. — DOI: 10.1146/annurev-nutr-071714-034330
3. Morris MS, Picciano MF, Jacques PF, Selhub J (2008). Plasma pyridoxal 5′-phosphate in the US population: the National Health and Nutrition Examination Survey, 2003-2004. American Journal of Clinical Nutrition;87(5):1446-1454. — DOI: 10.1093/ajcn/87.5.1446
4. Ulvik A, Midttun Ø, Pedersen ER, Eussen SJ, Nygård O, Ueland PM (2014). Evidence for increased catabolism of vitamin B-6 during systemic inflammation. American Journal of Clinical Nutrition;100(1):250-255. — DOI: 10.3945/ajcn.114.083196
5. Muhamad R, Akrivaki A, Papagiannopoulou G, Zavridis P, Zis P (2023). The Role of Vitamin B6 in Peripheral Neuropathy: A Systematic Review. Nutrients;15(13):2823. — DOI: 10.3390/nu15132823
6. Hvas AM, Juul S, Bech P, Nexø E (2004). Vitamin B6 Level Is Associated with Symptoms of Depression. Psychotherapy and Psychosomatics;73(6):340-343. — DOI: 10.1159/000080386
7. Cox TC, Bottomley SS, Wiley JS, Bawden MJ, Matthews CS, May BK (1994). X-linked Pyridoxine-Responsive Sideroblastic Anemia Due to a Thr388-to-Ser Substitution in Erythroid 5-Aminolevulinate Synthase. New England Journal of Medicine;330(10):675-679. — DOI: 10.1056/NEJM199403103301004
8. Mills PB, Footitt EJ, Mills KA, Tuschl K, Aylett S, et al. (2010). Genotypic and phenotypic spectrum of pyridoxine-dependent epilepsy (ALDH7A1 deficiency). Brain;133(7):2148-2159. — DOI: 10.1093/brain/awq143
9. Kaminiów K, Pajæk M, Pajæk R, Paprocka J (2021). Pyridoxine-Dependent Epilepsy and Antiquitin Deficiency Resulting in Neonatal-Onset Refractory Seizures. Brain Sciences;12(1):65. — DOI: 10.3390/brainsci12010065
10. Olaso-Gonzalez G, Inzitari M, Bellelli G, Morandi A, Barcons N, Viña J (2022). Impact of supplementation with vitamins B6, B12, and/or folic acid on the reduction of homocysteine levels in patients with mild cognitive impairment: A systematic review. IUBMB Life;74(1):74-84. — DOI: 10.1002/iub.2507
11. National Institutes of Health, Office of Dietary Supplements. Vitamin B6 — Health Professional Fact Sheet. — ods.od.nih.gov

PubMed Topic Searches

• PubMed — Vitamin B6 (pyridoxine) deficiency: symptoms and diagnosis
• PubMed — Isoniazid, pyridoxine, and prevention of peripheral neuropathy
• PubMed — Pyridoxine-responsive sideroblastic anemia and ALAS2
• PubMed — Pyridoxine-dependent epilepsy (ALDH7A1) and neonatal seizures
• PubMed — Vitamin B6 status, depression, and neurotransmitters

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Connections

• B6 Deficiency: Skin Rashes & Cracked Lips
• B6 Deficiency: Nerve Symptoms
• B6 Deficiency: Depression & Confusion
• B6 Deficiency: Anemia & Seizures
• Vitamin B6 Overview
• Vitamin B6 Toxicity Hub
• Vitamin B6 Benefits Hub
• B6 and Neurotransmitter Synthesis
• B6 and Homocysteine
• B6 and Sensory Neuropathy
• Vitamin B6 Food Sources
• Vitamin B6 History
• Complete Blood Count
• Homocysteine Test
• Iron Panel
• Vitamin B12
• Vitamin B9 (Folate)
• Vitamin B2 (Riboflavin)
• Iron
• Magnesium
• Peripheral Neuropathy
• Anemia
• Depression
• Epilepsy
• Tuna
• Salmon
• Chickpeas
• Bananas

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