Short answer. Adults need 1.3 mg of vitamin B6 a day, and children aged 1 to 13 need 0.5 to 1.0 mg, according to the NIH Office of Dietary Supplements. The adult upper limit is 100 mg. Pyridoxine and P-5-P are absorbed about equally, and long-term high doses can cause numbness and tingling in the hands and feet.
Pyridoxine and P-5-P at a glance
| Pyridoxine HCl | Pyridoxal 5'-phosphate (P-5-P, PLP) | |
|---|---|---|
| What it is | The most common form in supplements and fortified foods | The coenzyme form cells use; found in some supplements |
| What happens in the gut | Absorbed as free vitamin B6 in the jejunum | The phosphate is removed first, then the free vitamin is absorbed |
| Absorption | Similar to food, and does not differ substantially between forms (NIH ODS) | |
| High-dose safety | The form linked to reported nerve problems (Hadtstein 2021) | Same upper limit applies; no proof it is safer at high doses |
Source: NIH Office of Dietary Supplements; PubMed records under Sources.
What does vitamin B6 do in the body?
Vitamin B6 is the name for six related, water-soluble compounds: pyridoxine, pyridoxal and pyridoxamine, and a phosphate version of each. The working forms are pyridoxal 5'-phosphate (PLP) and pyridoxamine 5'-phosphate. PLP is a helper molecule in more than 100 enzyme reactions, most of them in protein metabolism (NIH Office of Dietary Supplements).
In practical terms, B6 helps the body build and break down amino acids, make neurotransmitters, release glucose from stored glycogen, form hemoglobin and support normal immune function. Together with folate and vitamin B12, it helps keep blood homocysteine in the normal range.
B6 also depends on riboflavin (vitamin B2). The enzyme that finishes making PLP uses a riboflavin-derived coenzyme, and in a study from Sheffield its activity in red blood cells rose when people took 2 mg or 4 mg of riboflavin a day (Mushtaq 2009). This is one reason B vitamins are often combined.
How much vitamin B6 do children and adults need?
The amounts are small. Infants have an Adequate Intake; from age 1 there is a Recommended Dietary Allowance (RDA). The Tolerable Upper Intake Level (UL) is the most a healthy person should take daily from food and supplements combined without medical supervision.
| Age | Recommended daily amount | Upper limit (UL) |
|---|---|---|
| 0–6 months | 0.1 mg (Adequate Intake) | Not set; breast milk, formula and food only |
| 7–12 months | 0.3 mg (Adequate Intake) | Not set; breast milk, formula and food only |
| 1–3 years | 0.5 mg | 30 mg |
| 4–8 years | 0.6 mg | 40 mg |
| 9–13 years | 1.0 mg | 60 mg |
| 14–18 years | 1.3 mg (boys), 1.2 mg (girls) | 80 mg |
| 19–50 years | 1.3 mg | 100 mg |
| 51 years and older | 1.7 mg (men), 1.5 mg (women) | 100 mg |
| Pregnancy | 1.9 mg | 80 mg (14–18), 100 mg (19+) |
| Lactation | 2.0 mg | 80 mg (14–18), 100 mg (19+) |
Source: NIH Office of Dietary Supplements.
The Daily Value on labels is 1.7 mg for adults and children 4 and older, so a typical 30 mg capsule shows 1,765% DV. That is about 23 times the adult RDA and 60 times the RDA for a child aged 1 to 3. Doses this size are a different category from everyday nutrition, and a child's dose belongs with the pediatrician. During pregnancy the RDA is 1.9 mg; the NIH advises asking a physician before taking a B6 supplement, because higher doses can approach the UL.
Can you get enough vitamin B6 from food?
Most people in the US do. Average intake is about 1.5 mg a day in women and 2 mg in men, and about 75% of the B6 in a mixed diet is absorbed (NIH Office of Dietary Supplements). Much of the B6 in fruits, vegetables and grains is bound to sugar molecules, which makes it less available than B6 from animal foods or supplements.
| Food and serving | Vitamin B6, mg |
|---|---|
| Chickpeas, canned, 1 cup | 1.1 |
| Beef liver, pan fried, 3 ounces | 0.9 |
| Yellowfin tuna, cooked, 3 ounces | 0.9 |
| Sockeye salmon, cooked, 3 ounces | 0.6 |
| Chicken breast, roasted, 3 ounces | 0.5 |
| Potatoes, boiled, 1 cup | 0.4 |
| Banana, 1 medium | 0.4 |
Source: NIH Office of Dietary Supplements.
A serving of chicken, a cup of potatoes and a banana already cover the adult RDA. High intakes from food have not been reported to cause side effects.
Who tends to run low on vitamin B6?
Isolated B6 deficiency is uncommon, and low B6 usually comes together with low B12 and folate. Blood levels are another matter. In the 2003 to 2004 national survey of more than 6,000 people aged 1 and older, most oral contraceptive users had plasma PLP below 20 nmol/L, the cut-off the US used to set the RDA, and women of childbearing age had lower PLP than men of the same age whether or not they took supplements (Morris 2008). The NIH reports that 24% of people who did not take B6 supplements and 11% of those who did had PLP below that line. Levels were also lower in smokers, people who are underweight, and teenagers.
The NIH lists further groups with low PLP: people with reduced kidney function, including dialysis; people with autoimmune or malabsorption conditions; and people who drink heavily, because acetaldehyde from alcohol interferes with PLP. Some medicines also lower B6 (see below).
Signs that justify a blood test include cracks at the corners of the mouth, scaling lips, a swollen tongue, confusion, a small-cell anemia, and weakened immunity. None of these is specific to B6, and mild deficiency can show no signs for months or years. The usual test is plasma PLP; the Food and Nutrition Board uses 20 nmol/L as the main marker of adequacy, while above 30 nmol/L has been the traditional adult target.
Is P-5-P better than pyridoxine?
P-5-P is sold as the "active" form, and it is the molecule cells use. But the phosphate group is removed in the gut, and the vitamin is absorbed as free B6. According to the NIH, absorption of B6 from supplements does not differ substantially between forms, and the body quickly clears most of a large dose in urine.
There is a reasonable argument that the form matters most at high doses. A 2021 review notes that pyridoxine is the form used in most supplements and the one linked to reported nerve problems, and proposes that high blood pyridoxine may block pyridoxal kinase, the enzyme that activates B6, mainly in nerves outside the brain (Hadtstein 2021). The authors call this the most plausible mechanism, not a proven one. Until it is tested in people, the same upper limits apply to both forms, and the dose matters more than the form.
How much vitamin B6 is too much?
Too much B6 from supplements has a well-described toxicity. In 1983 doctors reported seven adults who developed loss of coordination and severe loss of sensation after taking high daily doses of pyridoxine; four were severely disabled, and all improved after stopping (Schaumburg 1983). The NIH notes that 1 to 6 g a day for 12 to 40 months can cause severe, progressive sensory nerve damage, and that symptoms usually stop if the supplement is stopped as soon as they appear.
Lower doses are less clear. The US Food and Nutrition Board saw reports of nerve symptoms below 500 mg a day but no harm in patients averaging 200 mg a day for up to 5 years, halved that figure and set the adult UL at 100 mg. In 2023 the European Food Safety Authority set a much lower limit: 12 mg a day for all adults, including during pregnancy and lactation, and 2.2 to 10.7 mg for children depending on age (NIH Office of Dietary Supplements). A 2023 systematic review of 20 articles concluded that the evidence supports a neurotoxic role for B6 at high levels, with a mostly sensory neuropathy (Muhamad 2023).
Two practical points follow. First, add up B6 from every product: multivitamins, B-complexes, magnesium blends and protein powders often all carry it. Second, numbness, tingling or burning in the hands or feet is a reason to stop and call your doctor, who can check PLP. Other effects of excess include skin lesions, sun sensitivity, nausea and heartburn.
Does vitamin B6 interact with medicines?
The NIH Office of Dietary Supplements gives these examples. Anyone who takes them regularly should discuss B6 with their prescriber.
- Cycloserine increases the amount of B6 lost in urine.
- Valproic acid, carbamazepine and phenytoin speed up the breakdown of B6, which can lower PLP and raise homocysteine. Pyridoxine at 200 mg a day for 12 to 120 days can also lower blood levels of phenytoin and phenobarbital.
- Theophylline users often have low plasma PLP.
B6 is often paired with magnesium and with zinc in combination products. Pairing does not change the B6 upper limit, so count the B6 in those products too.
Which ASDHelp products contain vitamin B6?
Doses are copied from each label. Every product below except the chewable gives more than the European adult limit of 12 mg per serving; none exceeds the US adult UL of 100 mg.
- Vitamin B6 P-5-P: 30 mg as pyridoxal 5'-phosphate per capsule, 1,765% DV. Adults take 1 capsule a day; children only as directed by a healthcare professional. One capsule equals the UL for ages 1 to 3.
- Mag-B6: 30 mg B6 as P-5-P plus 100 mg magnesium per capsule. Adult format.
- Mag+Zinc+B6 Liquid: 50 mg B6 as pyridoxine HCl per 5 mL (approximately 1 teaspoon), with 30 mg magnesium and 5 mg zinc. One serving is above the UL for ages 1 to 3 (30 mg) and 4 to 8 (40 mg); the liquid can be measured in smaller amounts if a clinician sets a lower dose.
- Spectrum B Complex + Benfotiamine: 20 mg B6 as P-5-P per capsule, with riboflavin 5'-phosphate, folate and B12. Two capsules a day give 40 mg.
- Spectrum Formula Chewable + Iron: 2.5 mg B6 per 4 chewable tablets, inside a children's multivitamin with label directions from age 1.
Questions to take to your doctor
- Is there a reason to check my or my child's plasma PLP before starting B6?
- How much B6 do all of our current products add up to each day?
- Is a dose above the RDA needed, and for how many weeks or months?
- Do any of our medicines, such as phenytoin, valproic acid or theophylline, change the plan?
Sources
- NIH Office of Dietary Supplements. Vitamin B6 fact sheet for health professionals, updated June 16, 2023. ods.od.nih.gov
- National Academies. Dietary Reference Intakes tables (NCBI Bookshelf). ncbi.nlm.nih.gov/books/NBK545442
- Morris MS et al. Plasma pyridoxal 5'-phosphate in the US population: the National Health and Nutrition Examination Survey, 2003-2004. Am J Clin Nutr 2008. PMID 18469270
- Schaumburg H et al. Sensory neuropathy from pyridoxine abuse. A new megavitamin syndrome. N Engl J Med 1983. PMID 6308447
- Muhamad R et al. The Role of Vitamin B6 in Peripheral Neuropathy: A Systematic Review. Nutrients 2023. PMID 37447150
- Hadtstein F, Vrolijk M. Vitamin B-6-Induced Neuropathy: Exploring the Mechanisms of Pyridoxine Toxicity. Adv Nutr 2021. PMID 33912895
- Mushtaq S et al. Erythrocyte pyridoxamine phosphate oxidase activity: a potential biomarker of riboflavin status? Am J Clin Nutr 2009. PMID 19740970
These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure or prevent any disease. This article is educational and is not medical advice.