Yes, too much vitamin B-6 can be dangerous, and this can occur with B-6 supplements, B-complexes, high-potency multivitamins, and energy drinks. As shown in the table below and noted in our B Vitamin Supplements Review, the Daily Value (DV) for B-6, which is the total amount of B-6 you need per day from your diet and supplements, is, for adults, only about 1.7 mg. Although it safe to get somewhat more than that, the Tolerable Upper Intake Level (UL) for vitamin B-6 for adults is 100 mg, and exceeding this level increases your risk of adverse effects. In some cases, even lower doses have caused side effects. (Note: The Europe Union uses a more conservative daily upper limit of just 25 mg.)
The negative effects of too much vitamin B-6
High doses of vitamin B-6 can cause nerve damage and skin lesions, muscle twitching, increased risk of hip fracture, and other adverse effects. One clinical study found that 25 mg of B-6 taken daily as part of a B-complex vitamin increased the risk of heart attack, stroke and death in diabetes patients with advance kidney disease. Other research has shown that high doses of vitamin B-6 might increase the risk or worsen progression of various types of cancer, including lung cancer, rectal cancer, and nasopharyngeal cancer.
Too much B-6 when you don't expect it
By law, supplements in the U.S. are supposed to provide at least 100% of their listed amounts of ingredients when purchased and until a listed expiration date. Consequently, it is customary and acceptable for companies to put in a bit more (an "overage") than the listed amount of an ingredient to compensate for normal degradation. In fact, according the United States Pharmacopoeia (USP), up to 50% more is permitted for B vitamins. Therefore, if you are taking a multivitamin that lists 75 mg of B-6 (which is below the tolerable level but still about 4,000% of the Daily Value), it is possible that it provides more than the tolerable level — and you may be getting even more B-6 fortified foods, energy drinks, and other supplements!
Be aware that the mega doses of vitamin B-6 in some supplements appear to be driven more by marketing considerations than science. Unless you have been diagnosed with a deficiency in B-6, there is no good reason to take more than about 2 mg of B-6 per day and certainly no more than 25 mg.
Also, be aware that people taking certain medications may need to limit their intake of B-6 from supplements.
Get more information, including potential side-effects and drug interactions, plus ConsumerLab's tests, comparisons, and Top Picks among popular supplements, in the B Vitamin Supplements Review >>
- Dietary Reference Intakes (DRIs): Recommended Dietary Allowances and Adequate Intakes from the National Academies
- Daily Values from FDA Food Labeling: Revision of the Nutrition and Supplement Facts Labels 2016
- ULs (Tolerable Upper Intake Levels) from Dietary Reference Intakes (DRIs): Tolerable Upper Intake Levels, Vitamins from the National Academies
- * - Adequate Intake (AI)
- mg - milligram (1,000 milligrams = 1 gram)
- mcg - microgram (1,000 micrograms = 1 milligram)
- NE - DV not established
- ND - UL not determined
- m - male; f - female
- lact - lactating (breast feeding); preg - pregnant
- Age ranges are in years