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For further information, see CMDT Part 29-14: Vitamin B6 Deficiency

Key Features

  • Vitamin B6 deficiency most commonly occurs as a result of

    • Alcohol use disorder

    • Variety of medications, especially isoniazid, cycloserine, penicillamine, and oral contraceptives

  • Although inborn errors of metabolism and other pyridoxine-responsive syndromes are not clearly due to vitamin B6 deficiency, they commonly respond to high doses of the vitamin

Clinical Findings

  • Mouth soreness

  • Glossitis

  • Cheilosis

  • Weakness

  • Irritability

  • Severe deficiency can result in peripheral neuropathy, anemia, seizures

  • May be a correlation between low vitamin B6 levels and a variety of clinical conditions, including inflammatory diseases and certain cancers

  • May be seen concomitantly in patients who have common variable immunodeficiency


  • Serum pyridoxal phosphate levels

    • Normal levels vary per laboratory

    • They are typically > 5.0 ng/mL


  • Vitamin B6, 10–20 mg orally once daily

  • Patients taking medications that interfere with pyridoxine metabolism (such as isoniazid) may need doses as high as 100 mg/day

  • Patients with inborn errors of metabolism require up to 600 mg/day

  • Prophylaxis with vitamin B6 should be routinely given to

    • Patients receiving medications (such as isoniazid) that interfere with pyridoxine metabolism

    • Older patients

    • Patients with alcohol use disorder

  • B6 supplementation has no benefits on cardiovascular outcomes

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