Vitamin B6, or pyridoxine is a water-soluble micronutrient. B6 is an extremely important B vitamin which takes part in over 60 enzyme reactions in the body. It is important for the multiplication of cells and is therefore vital in pregnancy, immune system functioning, mucous membranes, skin, and red blood cells. Because these tissues multiply rapidly, they are in great need of vitamin B6. This vitamin is also important for brain chemistry as it is involved in the synthesis of all amino acid neurotransmitters such as serotonin, dopamine, melatonin, epinephrine, norepinephrine and others and is therefore critical for proper hormone balance.
The following foods have the highest concentration of vitamin B6. For a more expansive list on food sources of specific nutrients visit Health Canada's Dietary Reference Intakes for Vitamins or USDA's National Nutrient Database
Other food sources include:
The following is a list of most common uses for vitamin B6, although many other conditions have been treated using this vitamin. 
- Asthma: Possibly due to low levels of this vitamin, a tryptophan metabolism defect and reduced platelet transport of serotonin is seen in asthmatics. Supplementation with B6 has been used to correct this metabolism defect.
- Autism: Autism has been linked to defects in several brain neurotransmitters that require B6 for manufacturing. There appears to be a subgroup of individuals who do improve with supplementation. It appears to have a greater effect when combined with magnesium.
- Cardiovascular Disease (CVD): B6 deficiency leads to increased homocysteine levels in the blood, a metabolite of the amino acid methionine which can lead to atherosclerosis. There appears to be other mechanisms at play as well. B6 inhibits platelet aggregation which can also lead to inhibition of atherosclerosis. The vitamin also reduces total plasma lipids, total cholesterol, increases HDL (good cholesterol), and reduces blood pressure.
- Carpal Tunnel Syndrome: It is common to find a vitamin B6 deficiency is individuals with carpal tunnel syndrome. It may take up to 3 months of supplementation to see an improvement.
- Monosodium Glutamate Reaction: Proper metabolism of MSG requires sufficient vitamin B6. Supplementation may eliminate symptoms.
- Depression: Vitamin B6 levels are found to be quite low in individuals with depression especially those also taking birth control pills.
- Diabetes: Vitamin B6 can protect against diabetic neuropathy. Vitamin B6 in inhibits glycosylation of proteins, another complication of diabetes. It has also proven useful in treating gestational diabetes.
- Epilepsy: Vitamin B6 deficiency or dependency should be suspected in infants less than 18 months who experience convulsions and seizures. Supplementation must be strictly monitored professionally.
- Immune Enhancement: A deficiency in vitamin B6 depresses immunity.
- Kidney Stones: Vitamin B6 and magnesium supplementation can prevent calcium oxalate kidney stones in recurrent stone formers.
- Nausea and vomiting of Pregnancy: Vitamin B6 has shown significant relief of nausea and vomiting during pregnancy especially in combination with ginger.
- Osteoporosis: Low levels of vitamin B6 along with folic acid and vitamin B12 may be associated with osteoporosis due to an increase in homocysteine. Homocysteine can interfere with proper cross-linking of collagen which can lead to defective bone matrix.
- Premenstrual Syndrome: Supplementation of vitamin B6 appears to benefit most patients.
- convulsions (especially in children)
- glucose intolerance
- impaired nerve function
- cracking of the lips or tongue
- seborrhea or eczema
Vitamin B6 is one of a few water-soluble vitamins that is associated with some level of toxicity when either taken at high doses or at moderate doses over an extended period of time. Symptoms of nerve toxicity can ensue at doses greater than 2000mg/day.
- tingling sensation in the feet
- loss of muscle co-ordination
- degeneration of nerve tissue
Toxicity may also occur with chronic intake of greater than 500mg daily taken for many months or years and even chronic long-term use of 150mg a day. It is best to limit intake to 50mg/day.
Common Deficiency Tests 
- Plasma Homocysteine - a high level indicates a deficiency
- Urine Kynurenate - a high level indicates a deficiency
- EGOT Index - a high level indicates a deficiency
- Vitamin B6 is available as pyridoxine hydrochloride and the more active form, pyridoxal-5-phosphate. For most people, the pyridoxine form is sufficient as long as the co-factors for conversion are available (riboflavin and magnesium). The exception is people with liver disease. People with liver disease, especially liver cirrhosis have difficulty converting pyridoxine into its active form as this conversion takes place in the liver. Injectable pyridoxal-5-phosphate may be the most beneficial form in this case 
- It is typically beneficial to take Magnesium when taking Vitamin B6 to ensure that magnesium does not become depleted.
- The recommended dosages varies based on age and health status. To determine what your specific requirements are talk to your naturopathic doctor or other trained medical professional.
- Infants: 0.3mg (under 6 months); 0.6mg (6-12 months)
- Child: 1.0mg (1-3 years); 1.1mg (4-6 years); 1.4mg (7-10 years)
- Adolescent: 1.7mg (Males 11-14 years); 1.5mg (Females 11-14)
- Adult: 2.0mg (Males 15+ years); 1/6mg (Females 15+ years)
- Pregnancy: 2.2mg
- Lactation: 2.1mg
- Children: Supplementation is generally not indicated for children under 12 years of age.
- Adults: It is best to limit intake to 50mg/day.
- Seniors: Considered safe.
- Pregnancy and Breastfeeding: Women who are pregnant or breastfeeding should avoid doses greater than 100mg. Confirmed reports of teratogenicity are lacking.
- Contraindicated in known hypersensitivity. Yeast-free preparations are available for those sensitive to yeast found in some preparations.
Drug interactions include:
- Supportive or Beneficial:
- Amiodarone - Vitamin B6 may be beneficial in preventing or reversing inflammatory reaction (cutaneous photosensitivity with increased risk of sunburn) due to the drug.
- Anticonvulsive Medications and Related Barbiturates - Co-administration can mitigate adverse effects of drug and may enhance therapeutic effect (e.g., valproic acid and phenobarbital). Potential for accelerated drug metabolism (and decreased circulating levels), but substantive and consistent evidence lacking, and probably only with high-dose Pyridoxine. Vitamin B6 is a known anticonvulsant.
- Doxylamine - Combination of drug and vitamin B6 is effective in reducing symptoms of nausea and vomiting in pregnancy. Monitor as always during pregnancy. Ginger may also be beneficial.
- Methotrexate - Concomitant use of B6 may reduce adverse effects without impairing drug activity in treatment of rheumatoid arthritis.
- Oral Contraceptives - Drug can decrease serotonin levels. Vitamin B6 may reduce drug-related adverse effects.
- Tricyclic Antidepressants - Deficiency of vitamin B6 is more common in individuals with depression causing a decrease in serotonin synthesis. Co-administration may prevent or reverse depletion as well as augment clinical response to the drug through additive or synergistic effect.
- Addresses Drug-Induced Deficiency:
- Erythropoiesis-Stimulating Agents - Increased nutritional requirements may be needed while on drug. Even in absence of deficiency, supplementation can prevent or reverse adverse effects of drug. Supervise closely and monitor regularly, especially with renal failure.
- Furosamide and Related Loop Diuretics - Drug acutely increases urinary excretion of vitamin as well as vitamin C in chronic renal failure.
- Gentamicin and Related Aminoglycoside Antibiotics - Drug can interfere with B6 metabolism and contribute to depletion. Concomitant use can also prevent adverse effects of the drug.
- Haloperidol and Other Neuroleptic Agents - Concomitant use of the vitamin can prevent or reduce extrapyramidal symptoms induced by the drug.
- Hydralazine - Drug can bind to vitamin making it inactive. Co-administration may be beneficial but moderate-level doses warrant supervision and regular monitoring. Separate intake. Impairment of drug efficacy is probable.
- Isoniazid, Rifampin, and Related Antitubercular Agents - Drugs are antagonists to B6 and can produce a functional vitamin B6 deficiency. Separate intake.
- Neomycin - Drug use for longer than 2 weeks may have adverse effect on B6 status.
- Penicillamine - Drug is a vitamin B6 antagonist. Vitamin activity is impaired and overtime a deficiency may develop. Separating intake can avoid any decrease in either agent's activity.
- Phenelzine and Related Monoamine Oxidase-B Inhibitors - Drub may act as a vitamin B6 antagonist. Co-administration may prevent depletion and reverse adverse drug effects. Separate intake would reduce risk of any decrease in either agent's activity.
- Tetracylcine Antibiotics - Simultaneous intake of Pyridoxine and other B vitamins with tetracycline-class antibiotics can reduce absorption and bioavailability of both/all agents. Antibacterial effect on intestinal flora and gut ecology can produce secondary adverse effect on B-vitamin status and inflammatory processes. Separate intake if concurrent administration indicated or necessary.
- Theophylline/Aminophylline - Co-administration of vitamin B6 may prevent depletion and reverse adverse drug effects.
- Levodopa, Carbidopa, Benserazide, and Related Antiparkinsonian Medications' - Vitamin B6 accelerates peripheral metabolism of levodopa to dopamine, reducing the availability of dope for conversion to dopamine, and impairing the therapeutic activity of levodopa. Avoid supplementation with levodopa monotherapy. Not contraindicated with carbidopa or benserazide.
- Chemotherapy - Vitamin B6 may mitigate certain drug-induced adverse effects but can impair therapeutic activity of some agents. Use with Altretamine is generally contraindicated.
- Nutrient interactions include:
- Coenzyme Q10 - Exhibit a synergistic relationship. Endogenous synthesis of CoQ10 is dependent on adequate vitamin B6.
- Folic Acid - Both vitamins work together in regulating homocysteine.
- Iron - Iron along with Coenzyme Q10 and vitamin B6 may help to slow the progression of familial Alzheimer's disease.
- Magnesium - Exhibit an interdependent relationship both physiologically and clinically. Concurrent administration has been used for insomnia, Osgood-Schlatter Disease (along with zinc and manganese), and for treating social communication, and behavioural responses in children and adults with autism.
- Vitamin B2 - Both are involved in homocysteine regulation.
- Vitamin B12 - Both are involved in homocysteine regulation.
- Zinc - Zinc is involved in the activation of Pyridoxine. Zinc, vitamin B6, and magnesium are also all involved in the initial step in the conversion of essential fatty acids to prostaglandins. The two nutrients have been used together to treat mental illness and have been used in combination with magnesium and manganese for treatment of Osgood-Schlatter Disease
- Medlineplus 
- Murray Michael T (2005) Encyclopedia of Nutritional Supplements, The Essential Guide for Improving Your Health Naturally, Prima Publishing
- Bralley J Alexander and Lord Richard S (2005) Laboratory Evaluations in Molecular Medicine, Nutrients, Toxicants, and Cell Regulators Institute for Advances in Molecular Medince, GA
- Stargrove Mitchell Bebell, Treasure Jonathan, McKee Dwight L (2008) Herb, Nutrient, and Drug Interactions, Clinical Implications and Therapeutic Strategies. Mosby