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B-Complex Vitamins: What's Inside and Upper Limits

Also known as vitamin B complex, B-complex, B vitamins, B50, B100, super B complex

Short answer

A B-complex supplement combines the eight B vitamins: thiamin, riboflavin, niacin, pantothenic acid, B6, biotin, folate and B12 [9]. They are water-soluble, and extra amounts leave in urine, except B12, which the liver can store [10]. Niacin, B6 and folic acid each have upper limits for adults [3][5][7].

Last reviewed · 11 sources

What is B-Complex Vitamins?

The B vitamins are water-soluble [10]. The body uses them in many steps of metabolism. For example, B6 helps the body use and store energy from protein and carbohydrates and make hemoglobin [9]; biotin is a cofactor for enzymes that process fats, glucose and amino acids [6]; and B12 helps make red blood cells, keep the nervous system healthy and use folate [9].

Forms of B-Complex Vitamins you'll see on labels

  • Thiamin (B1)

    Usually thiamin mononitrate or thiamin hydrochloride [1].

  • Riboflavin (B2)

    Usually free riboflavin; some products use riboflavin 5'-phosphate. Riboflavin is yellow [2].

  • Niacin (B3)

    Nicotinic acid can cause skin flushing at high doses; nicotinamide (niacinamide) does not [3].

  • Pantothenic acid (B5)

    Most often calcium pantothenate; some products use pantethine [4].

  • Vitamin B6

    Most often pyridoxine hydrochloride; some products use pyridoxal 5'-phosphate (PLP) [5].

  • Biotin (B7)

    Can interfere with lab tests at high intakes [6].

  • Folate (B9)

    Folic acid, or 5-MTHF (also called L-methylfolate or methylfolate) [7].

  • Vitamin B12

    Cyanocobalamin is the most common form in supplements [8].

How much B-Complex Vitamins do adults need?

NIH lists these RDAs (AIs for pantothenic acid and biotin) for adults 19+. Reference values, not a personal recommendation.

GroupAmount per day
Thiamin (B1): men / women1.2 mg / 1.1 mg; pregnancy and lactation 1.4 mg
Riboflavin (B2): men / women1.3 mg / 1.1 mg; pregnancy 1.4 mg, lactation 1.6 mg
Niacin (B3): men / women16 mg NE / 14 mg NE; pregnancy 18 mg NE, lactation 17 mg NE
Pantothenic acid (B5), AI: adults5 mg; pregnancy 6 mg, lactation 7 mg
Vitamin B6: adults 19–501.3 mg; pregnancy 1.9 mg, lactation 2.0 mg
Vitamin B6: 51+ men / women1.7 mg / 1.5 mg
Biotin (B7), AI: adults30 mcg; lactation 35 mcg
Folate (B9): adults400 mcg DFE; pregnancy 600 mcg DFE, lactation 500 mcg DFE
Vitamin B12: adults2.4 mcg; pregnancy 2.6 mcg, lactation 2.8 mcg

Upper limit: Adults 19+: niacin 35 mg/day (supplemental niacin only) [3]; vitamin B6 100 mg/day [5]; folate 1,000 mcg/day from supplements and fortified foods [7]. No UL is set for thiamin, riboflavin, pantothenic acid, biotin or B12 [1][2][4][6][8]. The UK advises not more than 10 mg/day of B6 from supplements unless a doctor advises it [9].

How B-Complex Vitamins appears on a label

Units differ by vitamin. Niacin is counted in mg niacin equivalents (NE): 1 mg NE equals 1 mg niacin or 60 mg tryptophan [3]. Folate is in mcg dietary folate equivalents (DFE): 1 mcg DFE equals 0.6 mcg folic acid taken with food, or 0.5 mcg on an empty stomach [7]. Biotin and B12 are in mcg. B-complex products often far exceed the DV: B12 is typically 50–500 mcg [8], and pantothenic acid can reach 1,000 mg [4].

When to take B-Complex Vitamins

NIH does not name a best time of day for B-complex supplements. Folic acid is absorbed differently with and without food, which is why the DFE conversion changes on an empty stomach [7].

What to keep apart from B-Complex Vitamins

  • Multivitamins and single B vitamins

    Taking these together raises the chance of going over upper limits [11]. In one study, about half of multivitamin users already had excess niacin intakes [11].

  • Metformin and acid-reducing medicines (PPIs, H2 blockers)

    These can reduce vitamin B12 absorption [8]. Ask your doctor or pharmacist.

  • Methotrexate

    People taking methotrexate for cancer should ask their oncologist before taking folate, because it could interfere with the drug [7].

  • Anticonvulsants

    Long-term use is linked to lower biotin levels [6]. Ask your pharmacist.

  • Lab tests

    Biotin in B-complex products can cause wrong results on some lab tests [6]. Tell your doctor and the lab.

  • Folic acid and vitamin B12

    High folic acid intakes may mask a B12 deficiency until nerve damage occurs [7][9].

Foods that contain B-Complex Vitamins

  • Whole grains, plus fortified breads and cereals
  • Meat, poultry and fish
  • Eggs and milk
  • Liver and other organ meats
  • Leafy green vegetables, peas, chickpeas and beans (folate)
  • Potatoes and non-citrus fruit (B6)

Who should ask a doctor or pharmacist first

Ask a doctor or pharmacist first if you take metformin or acid-reducing medicines [8], methotrexate [7] or anticonvulsants [6], or if you have blood tests coming up (biotin) [6]. Pregnant women should consult a doctor before taking vitamin B6 supplements, because doses could approach the UL [5]. Adults over 50 are advised to get B12 mainly from fortified foods or supplements [11].

Keep B-Complex Vitamins in a routine that fits

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B-Complex Vitamins: questions people ask

Usually the eight B vitamins: thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), B6, biotin (B7), folate (B9) and B12 [9]. Amounts vary widely by product.

Most B vitamins have no upper limit [1][2][4][6][8]. Niacin, B6 and folic acid do, so check that your total from all products stays within them [3][5][7].

Yes. Taking 1–6 g a day of pyridoxine for 12–40 months can cause severe nerve damage [5]. The NHS says 200 mg or more a day can cause loss of feeling in the arms and legs [9].

High doses of nicotinic acid can cause skin flushing. Nicotinamide (niacinamide) does not, because of its slightly different structure [3].

Folic acid is the synthetic form. 5-MTHF (methylfolate) is a form of folate also found in some supplements [7]. Conversion factors for 5-MTHF to DFE have not been formally set [7].

Check the totals first. People who take a multivitamin plus single supplements are more likely to go over upper limits [11].

Plant foods do not naturally contain B12 [8]. The NHS says vegans may not get enough from diet; fortified cereals and nutritional yeast are sources [8][9].

NIH does not set a time of day. The folate conversion differs with and without food [7].

Sources

  1. Thiamin: Fact Sheet for Health Professionals — NIH Office of Dietary Supplements
  2. Riboflavin: Fact Sheet for Health Professionals — NIH Office of Dietary Supplements
  3. Niacin: Fact Sheet for Health Professionals — NIH Office of Dietary Supplements
  4. Pantothenic Acid: Fact Sheet for Health Professionals — NIH Office of Dietary Supplements
  5. Vitamin B6: Fact Sheet for Health Professionals — NIH Office of Dietary Supplements
  6. Biotin: Fact Sheet for Health Professionals — NIH Office of Dietary Supplements
  7. Folate: Fact Sheet for Health Professionals — NIH Office of Dietary Supplements
  8. Vitamin B12: Fact Sheet for Health Professionals — NIH Office of Dietary Supplements
  9. Vitamin B — NHS
  10. Vitamins — MedlinePlus Medical Encyclopedia, U.S. National Library of Medicine
  11. Multivitamin/mineral Supplements: Fact Sheet for Health Professionals — NIH Office of Dietary Supplements

Educational information, not medical advice. The amounts above are official reference values, not a recommendation for you. Check with your doctor or pharmacist before starting or changing supplements, especially if you take medication, are pregnant or have a health condition. Supin sells a subscription, not supplements. Last reviewed .

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