B-Complex Vitamins: Active Forms and the B6 Megadose Trap

Costs are list prices at each brand’s store or Vitacost, checked October 13, 2026.

Our pick

Nature Made Super B-Complex
USP Verified · 2 mg of B6 · $0.083 a day

Nature Made’s own site lists it as discontinued. Amazon still sells it; if it sells out, our pick is Nature's Bounty Super B-Complex.

Want the lowest cost? Nature's Bounty Super B-Complex is $0.079 a day with 5 mg of B6. It is not on a testing list.

Nature's Bounty Super B-Complex
$0.079 a day · folic acid, cyanocobalamin

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Want methylfolate and methyl B12? See Thorne B-Complex #12 under the forms section; it is over the B6 and niacin limits.

Where to go next

Best B-complex: all 12 we score, ranked.
B-complex dosage guide: how much of each B you need, and a label check.
B-complex prices: what a day costs for each product.

What a B-complex is

A B-complex has the eight B vitamins: B1 (thiamin), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6, B7 (biotin), B9 (folate) and B12. Your body uses them to turn food into energy, build DNA and make nerve and blood cells (NIH). NIH says most Americans eat enough B12, folate and thiamin, so a B-complex mostly helps people who run low.

Where you get them from food. Folate is in dark green leafy vegetables, fruits, nuts, beans, peas, eggs, dairy, meat and grains. B6 is richest in fish, organ meats, potatoes and fruit other than citrus. B12 comes naturally only from animal foods, though some cereals and nutritional yeasts add it (NIH).

Signs you may be low

NIH lists tiredness, nerve changes such as numbness, a type of anemia, a sore tongue and a fast heartbeat as signs of low B12. They can take years to show, because the body stores B12. Only a blood test confirms it.

Who may need a B-complex

NIH names these groups as more likely to run low. A blood test, not a guess, shows whether you are.

Who	Which B	What NIH says
Older adults, or anyone with a stomach or bowel disorder or surgery	B12	NIH: 3% to 43% of older adults have a low B12 level, depending on the test.
Vegans and vegetarians	B12	NIH: B12 comes naturally only from animal foods.
People who take metformin or an acid reducer	B12	NIH: both can lower how much B12 you absorb.
Women who are pregnant or could become pregnant	Folic acid	CDC advises 400 mcg of folic acid a day. A B-complex is not a prenatal vitamin.
People who drink heavily	Thiamin (B1), folate, B6	NIH: alcohol use disorder is the most common cause of thiamin shortage in rich countries.

Does a B-complex work?

Each common claim, by the best human evidence we found.

Goal	Evidence	What the research shows
Fixing a shortage	Needed if low	NIH: a B12 shortage can cause tiredness, nerve changes and anemia, and a folate shortage causes the same kind of anemia. A blood test shows a shortage, and a doctor treats it. Who is more likely to run low.
Heart attack and early death	Not shown	B vitamins lower homocysteine, a blood marker. A Cochrane review of 15 trials and 71,422 people found no change in heart attacks or in deaths from any cause (Martí-Carvajal 2017). More.
Stroke	Small, unsure for the US	The same review found slightly fewer strokes: 4.3% against 5.1%. A 2024 review of 14 trials found fewer strokes where food had little or no added folic acid, and no benefit where it did (Zhang 2024). The US adds folic acid to grain (NIH), so the result may not apply here.
Energy	Not shown unless low	NIH: B12 supplements do not appear to improve athletic performance or endurance in people who have enough B12. Trials that found a lift measured how people rated themselves, tested vitamin and mineral products, not B vitamins alone, and one was paid for by Bayer, which makes Berocca (Kennedy 2010). More.
Stress and mood	Mixed	A 2019 review of 12 trials found a small drop in stress scores and no change in anxiety; the change in depression was not significant (Young 2019; Bayer Healthcare paid part of it). One trial found stress scores no different from placebo (Camfield 2013). In another the placebo group improved as much, and a vitamin maker paid for it (Downey 2019, Blackmores).
Memory and thinking	Not shown	A Cochrane review found that B vitamins in healthy adults, mostly in their 60s and 70s, probably have little or no effect on thinking for up to 5 years (Rutjes 2018). A review of 11 trials in 22,000 people found the same for lowering homocysteine (Clarke 2014).
Hair, skin and nails (biotin)	Not shown in healthy people	NIH: these claims are supported, at best, by only a few case reports and small studies.

How much you need

Adults need only small amounts: for example 1.3 mg of B6, 400 mcg DFE of folate and 2.4 mcg of B12 a day (NIH). DFE counts folate by how well you absorb it. Most B vitamins have no upper limit. B6, niacin and folic acid do. Every B’s daily amount and limit.

The B6 limit: why B-50 and B-100 need a label check

Too much B6 over months can damage nerves, mostly causing tingling or numbness (Muhamad 2023). NIH’s limit is 100 mg a day; the EU’s food safety agency set 12 mg in 2023. B-50 and B-100 mean about 50 or 100 mg of several B vitamins, including B6, in each pill. Of the 12 B-complexes we score, 6 have 50 mg or more of B6 in a serving; Jarrow B-Right has 35 mg. Check your label.

Side effects

B6: too much over months can damage nerves. Tingling or numbness? Stop and call your doctor.
Niacin: 30 mg or more of nicotinic acid often flushes the skin red (NIH). Niacinamide does not flush, but NIH still counts it toward the 35 mg limit.
Riboflavin: turns urine bright yellow. That is harmless.
Folic acid: large amounts may hide a B12 shortage; NIH says that question is not settled.

Do vitamin forms matter?

Folate. NIH says methylfolate (5-MTHF), the form your cells use, absorbs as well as or better than folic acid. Some people carry a gene variant (MTHFR 677C>T) that makes the body convert folate less well; NIH calls the research on methylfolate for them inconclusive.
Before pregnancy. NIH reports that the CDC advises 400 mcg of folic acid a day, not methylfolate, for women who could become pregnant, even with that variant.
B12. NIH says no evidence shows that B12 absorption differs by form.

Want methylfolate and methyl B12 anyway? Thorne B-Complex #12 has both and is on a testing list, but it has 23.4 mg of B6 and 80 mg of niacin, both over the limits below. Testing checks what is in the bottle, not the dose. If you could become pregnant, ask your doctor first: the CDC advises folic acid.

Thorne B-Complex #12
NSF/ANSI 173 · $0.43 a day

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Ask a doctor first if

You are pregnant or could become pregnant. CDC and USPSTF advise folic acid. A B-complex is not a prenatal vitamin.
You take metformin or an acid reducer. NIH says both can lower B12. Ask for a B12 blood test.
You take a seizure medicine or methotrexate. NIH says about 200 mg a day of B6 can lower phenytoin and phenobarbital levels, and people taking methotrexate for cancer should ask their oncologist before taking folate.
You have blood tests coming. NIH and FDA say high-dose biotin (10 mg, as in some hair and nail pills) can cause false thyroid and troponin results. Most B-complexes hold far less, but tell your lab what you take.
You might be low in B12. NIH says large amounts of folic acid can fix the anemia of a B12 shortage but not the nerve damage. Get a B12 test first.

Questions people ask

Does a B-complex boost energy?

Not if you already get enough. NIH says B12 supplements do not appear to improve athletic performance or endurance in people with enough B12, and that they have no benefit for performance without a shortage. A real shortage of B12 or folate can cause tiredness (NIH), and a blood test shows it. A few small trials of vitamin and mineral products found people rated themselves as less tired or more alert. Those trials used products with more than B vitamins, relied on self-ratings, and one was paid for by Bayer (Kennedy 2010).

Are active/methylated forms better?

We found no proof that one form works better for your health. NIH says 5-MTHF, the active folate, absorbs as well as or better than folic acid. For B12, NIH says no evidence shows that absorption differs by form. For people with a common MTHFR gene variant, NIH calls the research on 5-MTHF inconclusive, and CDC still advises folic acid, not 5-MTHF, for women who could become pregnant.

Do B vitamins protect the heart by lowering homocysteine?

Not in the trials we read. Folic acid, B6 and B12 do lower homocysteine, a blood marker. A Cochrane review of 15 trials and 71,422 people found no difference in heart attacks (7.1% against 6.0%) or in deaths from any cause (Martí-Carvajal 2017). It found slightly fewer strokes, 4.3% against 5.1%. NIH reaches the same view for heart disease: these supplements lower homocysteine but not the risk of it.

What's the B-50/B-100 problem?

B-50 and B-100 pills hold about 50 or 100 mg of most B vitamins, including B6. NIH’s upper limit for B6 is 100 mg a day from food and supplements together. EFSA, the European food safety agency, set 12 mg a day in 2023. Large amounts of B6 over months can damage nerves. Of the 12 B-complexes we score, 6 have 50 mg or more of B6 in a serving and 3 have 100 mg. Tingling or numbness in hands or feet? Stop the B6 and call your doctor.

B-Complex Vitamins: Active Forms, the B6 Megadose Trap, and What They Actually Do