A multivitamin is a preparation intended to supplement a human diet with vitamins, dietary minerals and other nutritional elements. Such preparations are available in the form of tablets, capsules, pastilles, powders, liquids and injectable formulations. Other than injectable formulations, which are only available and administered under medical supervision, multivitamins are recognized by the sell house fast Codex Alimentarius Commission (the United Nations’ authority on food standards) as a category of food.[1] Multivitamin supplements are commonly provided in combination with minerals. A multivitamin/mineral supplement is defined in the United States as a supplement containing 3 or more vitamins and minerals that does not include herbs, hormones, or drugs, where each vitamin and mineral is included at a dose below the tolerable upper level, as determined by the Food and Drug Board, and does not present a risk of adverse health effects.[2] The terms multivitamin and multimineral are often used interchangeably. There is no scientific definition for either.[3] Linguistically, the terms are compounded words of which meaning can be derived in that capacity.

Many multivitamins are formulated and/or labeled to differentiate consumer sectors e.g. prenatal, children, mature or 50+, men’s, women’s, diabetic, stress or megavitamin. Consumer multivitamin formulas are available as tablets, capsules, bulk powder, or liquid. Once and twice per day multivitamin formulas dominate common usage, although some formulas are designed for consumption 3–7 times per day or even allow hourly use.
Compositional variation amongst brands and lines allows substantial consumer choices. Modern multivitamin products roughly classify into RDA (recommended dietary allowance) centric multivitamins with or without iron, RDA centric multivitamin/multimineral formulas with or without iron, higher potency formulas with mostly above RDA components with or without iron, and more specialized formulas by condition, such as for diabetics or by less common components, such as diversified antioxidants, herbal extracts or premium vitamin and mineral forms. Legally, the United States Food and Drug Administration allows a multivitamin to be called “high potency” if at least two-thirds of its nutrients have at least 100 percent of the DV. In practice, “high potency” usually means substantially increased vitamin C and Bs with some other enhanced vitamin and mineral levels, but some minerals may still be much less than DV.
Some components are typically much lower than RDA amounts, often for anything goes diet cost reasons, e.g. biotin, usually the most expensive vitamin component, at over $4000 per active pound, is typically added in at only 5%-30% of RDA in many one per day formulations. Biotin is required to be present at 100% of the value of the B-vitamins for they to be absorbed by the body. Any B-vitamins that cannot be absorbed due to a lack of biotin are eliminated by the body. Likewise, boron and magnesium are considered essential for the bioavailability and absorption of Vitamin D and calcium. Sometimes low content composition is for population subgroups, where the RDA would be inappropriate, such often occurs with iron, where the original population intake calculation was ca 12–13 mg iron per day by including menstruating females but some percentage of HFE variant gene bearing males with high iron retention, and others, may only need as little as ~1 mg iron per day including the normal dietary contribution.
Basic commercial multivitamin supplement products often contain the following ingredients: vitamin C, B1, B2, B3, B6, folic acid (B9), B12, B5 (pantothenate), H (biotin), A, E, D3, K1, potassium iodide, cupric (sulfate anhydrous, picolinate, sulfate monohydrate, trioxide), selenomethionine, borate(s), zinc, calcium, magnesium, chromium, manganese, molybdenum, betacarotene, and iron. Other formulas may include additional ingredients such as other carotenes (e.g. lutein, lycopene), higher than RDA amounts of B, C or E vitamins including gamma-tocopherol, “near” B vitamins (inositol, choline, PABA), trimethylglycine (anhydrous betaine), betaine hydrochloride, vitamin K2 as menaquinone-7, lecithin, citrus bioflavinoids or nutrient forms variously described as more easily absorbable.

Many multivitamins are formulated and/or labeled to differentiate consumer sectors e.g. prenatal, children, mature or 50+, men’s, women’s, diabetic, stress or megavitamin. Consumer multivitamin formulas are available as tablets, capsules, bulk powder, or liquid. Once and twice per day we buy any house multivitamin formulas dominate common usage, although some formulas are designed for consumption 3–7 times per day or even allow hourly use.Compositional variation amongst brands and lines allows substantial consumer choices. Modern multivitamin products roughly classify into RDA (recommended dietary allowance) centric multivitamins with or without iron, RDA centric multivitamin/multimineral formulas with or without iron, higher potency formulas with mostly above RDA components with or without iron, and more specialized formulas by condition, such as for diabetics or by less common components, such as diversified antioxidants, herbal extracts or premium vitamin and mineral forms. Legally, the United States Food and Drug Administration allows a multivitamin to be called “high potency” if at least two-thirds of its nutrients have at least 100 percent of the DV. In practice, “high potency” usually means substantially increased vitamin C and Bs with some other enhanced vitamin and mineral levels, but some minerals may still be much less than DV.Some components are typically much lower than RDA amounts, often for cost reasons, e.g. biotin, usually the most expensive vitamin component, at over $4000 per active pound, is typically added in at only 5%-30% of RDA in many one per day formulations. Biotin is required to be present at 100% of the value of the B-vitamins for they to be absorbed by the body. Any B-vitamins that cannot be absorbed due to a lack of biotin are eliminated by the body. Likewise, boron and magnesium are considered essential for the bioavailability and absorption of Vitamin D and calcium. Sometimes low content composition is for population subgroups, where the RDA would be inappropriate, such often occurs with iron, where the original population intake calculation was ca 12–13 mg iron per day by including menstruating females but some percentage of HFE variant gene bearing males with high iron retention, and others, may only need as little as ~1 mg iron per day including the normal dietary contribution.Basic commercial multivitamin supplement products often contain the following ingredients: vitamin C, B1, B2, B3, B6, folic acid (B9), B12, B5 (pantothenate), H (biotin), A, E, D3, K1, potassium iodide, cupric (sulfate anhydrous, picolinate, sulfate monohydrate, trioxide), selenomethionine, borate(s), zinc, calcium, magnesium, chromium, manganese, molybdenum, betacarotene, and iron. Other formulas may include additional ingredients such as other carotenes (e.g. lutein, lycopene), higher than RDA amounts of B, C or E vitamins including gamma-tocopherol, “near” B vitamins (inositol, choline, PABA), trimethylglycine (anhydrous betaine), betaine hydrochloride, vitamin K2 as menaquinone-7, lecithin, citrus bioflavinoids or nutrient forms variously described as more easily absorbable.While multivitamins can be a valuable tool to correct dietary imbalances, it is worth exercising basic caution before taking them, especially if any medical conditions exist. In particular, pregnant women should generally consult their doctors before taking any multivitamins: for example, either an excess or deficiency of vitamin A can cause birth defects.[8] Some analyses have suggested that long-term use of beta-carotene, vitamin A, and vitamin E supplements may shorten life rather than extend it, with the additional risk being particularly large in smokers.[9]

Severe vitamin and mineral deficiencies require medical treatment and can be very difficult to treat with common over-the-counter multivitamins. In such situations, special vitamin or mineral forms with much higher potencies are available, either as individual components or as specialized formulations, sometimes requiring a prescription.

Multivitamins in large quantities may pose a risk of an acute overdose, due to the toxicity of some components, principally iron. However, in contrast to iron tablets, which can be lethal to children,[10] toxicity from overdoses of multivitamins are very rare.[11] There appears to be little risk to supplement users of experiencing acute side effects due to excessive intakes of micronutrients.[12] There also are strict limits on the retinol content for vitamin A during pregnancies that are specifically addressed by prenatal formulas. Additionally, various medical conditions and medications may adversely interact with multivitamins.

Many common brand supplements in the United States contain levels above the DRI/RDA amounts for some vitamins or minerals.