Vitamin B6 is a water-soluble B vitamin the body uses in more than 100 enzyme reactions, mostly in protein metabolism. As a supplement, usually pyridoxine hydrochloride, it is used to cover low intake and has been studied for morning sickness, PMS, heart disease and memory.
Also known as: pyridoxine, pyridoxine hydrochloride, pyridoxal 5'-phosphate, P5P, PLP.
ODS lists a Recommended Dietary Allowance of 1.3 mg a day for adults 19 to 50; from age 51 it is 1.7 mg for men and 1.5 mg for women (1.9 mg in pregnancy, 2.0 mg while breastfeeding). The Tolerable Upper Intake Level for adults, including in pregnancy, is 100 mg a day from food and supplements. ODS notes that in 2023 the European Food Safety Authority set a lower adult upper limit of 12 mg a day.
It is sold in the US as a dietary supplement. Under the 1994 dietary supplement law (DSHEA), FDA does not approve dietary supplements before they are marketed, and the maker, not FDA, is responsible for safety and labeling. B6 comes in multivitamins, B-complex products and on its own; ODS says the body absorbs large doses well but quickly removes most of it in the urine.
What studies show, per ODS: in two trials, 30 to 75 mg of pyridoxine a day reduced nausea in pregnant women, but a Cochrane review could not draw firm conclusions, and B6 combined with the antihistamine doxylamine has been linked to about 70% less nausea and vomiting in pregnancy. ODS says pregnant women should talk to a doctor before taking B6 because doses can approach the upper limit. For PMS, some evidence suggests benefit but most studies were poor quality. Large trials found little evidence that B6, alone or with folic acid and B12, lowers heart disease or stroke risk, and reviews found insufficient evidence that it helps thinking or memory.
The main risk is nerve damage. ODS says taking 1 to 6 g of pyridoxine a day for 12 to 40 months can cause severe, progressive sensory neuropathy with loss of control of body movements; symptoms usually stop if the supplement is stopped as soon as they appear. Other effects of too much B6 include painful skin lesions, sun sensitivity, nausea and heartburn. Interactions, per ODS: the tuberculosis drug cycloserine increases B6 loss in urine; some seizure drugs (valproic acid, carbamazepine, phenytoin) lower B6 levels, and 200 mg a day of pyridoxine can lower blood levels of phenytoin and phenobarbital; people taking theophylline often have low B6 levels.
We could not find a single published half-life or time to peak for vitamin B6 that applies to a supplement dose, so we do not list one. ODS says the body absorbs large doses well but quickly removes most of it in the urine.
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