Vitamin B6 in pregnancy: evidence and safety

How does vitamin B6 work?

The active coenzyme form, pyridoxal 5' phosphate, is what actually does the work, and it does a great deal of it. NIH ODS describes vitamin B6 coenzymes as involved in more than 100 enzyme reactions, mostly concerned with protein metabolism, with PLP and PMP handling amino acid metabolism and PLP also working on one-carbon units, carbohydrates, and lipids. ODS further lists roles in cognitive development through the biosynthesis of neurotransmitters, in maintaining normal homocysteine levels, in gluconeogenesis and glycogenolysis, in immune function including lymphocyte and interleukin-2 production, and in hemoglobin formation. Worth being clear about the gap: none of that explains why B6 eases pregnancy nausea. The nausea evidence is clinical, and these sources do not establish the pathway behind it.

What does the evidence say about vitamin B6 in pregnancy?

• The recommended vitamin B6 intake in pregnancy is 1.9 mg per day, with an upper limit of 100 mg per day. 1
• Taking pyridoxine well above the 100 mg per day limit for a long time has been linked to sensory nerve problems in adults, numbness and tingling, which is part of why that limit exists. 1
• ACOG recommends 10 to 25 mg of vitamin B6 by mouth every 6 to 8 hours, alone or with doxylamine, as a first-choice option for nausea and vomiting in pregnancy, a total daily amount well below the NIH 100 mg limit. 2
• Hundreds of thousands of pregnancies have used pyridoxine at recommended doses without an identified increase in birth-defect risk. 3
• Pregnancy Smart's Supplement Facts panels list pyridoxine HCl at 150 mg per three-capsule serving in the Nausea & Digestive Support formula, and 75 mg per three-capsule serving in the Immune & Respiratory Support formula. 4

What's on the label?

ODS states that the most common B6 vitamer in supplements is pyridoxine hydrochloride, though some products contain PLP, and that absorption from supplements is similar to absorption from food and does not differ substantially among the various forms. So paying more for a P5P product is not supported by an absorption argument, and the number that matters is the total daily milligrams from every source measured against the 100 mg pregnancy upper limit.

• Nausea and Digestive Support lists Vitamin B6 at 150 mg per serving, as printed on the Supplement Facts panel.
• Immune and Respiratory Support lists Vitamin B6 at 75 mg per serving, as printed on the Supplement Facts panel.

When comparing any brand, read the Supplement Facts panel for the exact per-serving amount and look for third-party test results. Add any prenatal-vitamin amount of the same ingredient to your daily total before comparing against a pregnancy upper limit.

What should I know before taking vitamin B6?

Please consult your healthcare provider before adding this supplement to a prenatal regimen, particularly if you are on prescription medication or have a scheduled procedure. Supplement contents are not FDA-verified, so a labeled dose and an actual dose can differ; look for third-party-tested brands.