Vitamin B6, also known as pyridoxine, is a crucial nutrient that plays a significant role in a wide range of bodily functions. It is essential for protein metabolism, red blood cell production, and the creation of neurotransmitters like serotonin and dopamine. Vitamin B6 is also involved in immune function, brain development, and maintaining normal levels of homocysteine, an amino acid in the blood. Adequate levels of vitamin B6 are necessary for optimal health, including proper nerve function and cognitive health. As a water-soluble vitamin, B6 needs to be regularly consumed in the diet, as the body does not store it in large amounts.
Deficiency in vitamin B6, though relatively rare, can lead to a range of health issues. Symptoms include anemia, skin rashes, cracked and sore lips, a swollen tongue, mood changes, weakened immune function, and in severe cases, confusion and seizures. Vitamin B6 deficiency is often associated with low levels of other B vitamins, such as B12 and folic acid, and can be caused by malabsorption syndromes, certain medications, alcoholism, or an inadequate diet. Vitamin B6's absorption and utilization are influenced by dietary protein, magnesium, and other B vitamins.
Toxicity from vitamin B6 is typically related to excessive supplementation and is rare from food sources. High doses of vitamin B6 over a prolonged period can lead to nerve damage, causing numbness and pain in the hands and feet, and in severe cases, could potentially cause neurological problems. The upper intake level for adults is set to avoid the risk of such nerve damage. To maintain adequate levels of vitamin B6, a diet including poultry, fish, potatoes, chickpeas, bananas, and fortified cereals is recommended. Regular monitoring of vitamin B6 levels is generally not necessary, except for individuals with specific medical conditions or dietary restrictions.
To maintain healthy Vitamin B6 levels:
Consume a varied diet rich in vitamin B6 sources, including poultry, fish, potatoes, non-citrus fruits, chickpeas, and fortified cereals.
Ensure adequate protein intake, as it aids in vitamin B6 absorption and utilization.[Miller, 1985]
Be aware of factors that can deplete vitamin B6, such as excessive alcohol consumption and certain medications.
Consider other nutrients that influence B6 metabolism, like magnesium and other B vitamins. A balanced diet or a B-complex supplement may be beneficial.
Vitamin B6 (Pyridoxine) can be measured in: ng/mL, nmol/L, µg/100mL, µg/dL, µg/L, µg%
Reference ranges represent typical values for healthy individuals. Your healthcare provider must interpret your specific results.
| Age Range | Gender | Unit | Optimal | Normal | Source |
|---|---|---|---|---|---|
| All ages | All genders | ng/mL | - | 9.5 - 24 | Rifai, 2023 |
Important for immune function, as it's involved in the production of antibodies and cytokines. It also aids in the growth and function of immune cells like lymphocytes. B6 deficiency impairs the immune response. [Qian, 2017][Meydani, 1991]
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Vitamin B6 is involved in the conversion of homocysteine to cysteine. Adequate levels of vitamin B6 are necessary to maintain normal homocysteine levels. A deficiency in vitamin B6 can result in elevated homocysteine, which is a risk factor for cardiovascular disease.[Selhub, 1999]
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Vitamin B6 is a group of three related water-soluble compounds: pyridoxine (the most common supplement form), pyridoxal, and pyridoxamine. The blood test typically measures pyridoxal-5-phosphate (P5P or PLP) — the biologically active coenzyme form that the body uses for over 100 enzymatic reactions. P5P is the most clinically meaningful measure of B6 status, as it reflects tissue availability better than total plasma B6.
B6 is essential for amino acid metabolism (transamination, decarboxylation), neurotransmitter synthesis (serotonin, dopamine, GABA, norepinephrine), haemoglobin production, gluconeogenesis (glucose production from amino acids), immune function, and homocysteine metabolism (converting homocysteine to cystathionine via the transsulphuration pathway). See the broader B vitamins blood test guide for context on the full B-vitamin panel.
Reference ranges vary between laboratories. Some labs report as mg/L or ng/mL. Use the blood test unit converter to convert. Note: plasma B6 can be falsely elevated in people taking supplements recently before testing.
Vitamin B6 deficiency is uncommon in developed countries in healthy adults eating varied diets. However, it is more prevalent in people with certain risk factors:
Symptoms of B6 deficiency include: microcytic anaemia (because B6 is needed for haem synthesis), peripheral neuropathy, dermatitis with cheilosis (cracked corners of the mouth) and glossitis (inflamed tongue), depression and confusion, and weakened immune function. B6 deficiency often co-occurs with B12 and folate deficiency — resulting in elevated homocysteine. Check homocysteine and vitamin B12 together.
Unlike most water-soluble vitamins, B6 can cause toxicity with chronic high-dose supplementation. Sensory neuropathy — characterised by numbness, tingling, and pain in hands and feet — is the most serious adverse effect. This has been reported at doses above 200 mg/day and can be irreversible in severe cases. The EU has recently lowered the maximum permitted dose in supplements to 12–25 mg/day in some countries due to toxicity concerns. The US Tolerable Upper Intake Level is set at 100 mg/day for adults.
Note: very high plasma P5P from recent supplementation does not necessarily indicate harm — what matters is sustained levels over time. However, any supplement dose above 50 mg/day warrants discussion with a healthcare provider.
Most laboratories define normal plasma pyridoxal-5-phosphate (P5P) as 30–143 nmol/L (approximately 7.5–35 µg/L). Values below 20 nmol/L indicate deficiency. However, reference ranges vary between labs, and interpretation should account for recent supplementation.
The RDA is 1.3 mg/day for adults aged 19–50; 1.5–1.7 mg/day for those over 50; 1.9 mg/day during pregnancy; and 2.0 mg/day while breastfeeding. For most people, diet (poultry, fish, potatoes, bananas, fortified cereals) provides adequate B6. Supplementation above 50 mg/day is generally not recommended without medical supervision due to neuropathy risk at high doses.
Yes — sensory peripheral neuropathy from B6 toxicity is a real risk at sustained high doses (typically >200 mg/day from supplements, though cases have been reported at lower doses in sensitive individuals). The EU has tightened regulations on B6 supplement doses in response. If you are taking a high-dose B6 supplement, monitor plasma P5P levels and discuss with your healthcare provider.
Some clinical trials support modest benefits of B6 (50–100 mg/day) for PMS symptoms, particularly mood-related symptoms like depression and irritability, possibly through enhancing serotonin and dopamine synthesis. A 2016 Cochrane review found positive but limited-quality evidence. If considering B6 for PMS, discuss with your healthcare provider and use the minimum effective dose.
The best dietary sources include chicken, turkey, and other poultry; salmon and tuna; potatoes and starchy vegetables; non-citrus fruits (especially bananas); chickpeas; and fortified cereals. A varied diet incorporating these foods generally provides sufficient B6 without supplementation.
B6 (as P5P) is the cofactor for cystathionine beta-synthase, the enzyme that converts homocysteine to cystathionine in the transsulphuration pathway. Without adequate B6, this pathway slows and homocysteine accumulates in the blood. B6 deficiency is one of the three main nutritional causes of elevated homocysteine (alongside folate and B12 deficiency). Testing B6 alongside homocysteine, B12, and folate provides a complete picture of one-carbon metabolism.
This page is for educational purposes only. Vitamin B6 reference ranges vary between laboratories and test methods. High-dose B6 supplementation carries real risks; always discuss supplementation above 50 mg/day with a healthcare provider. Health3 is a tracking and awareness tool, not a diagnostic service.
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