Vitamin B12: The Fact Sheet

Updated: January 9, 2026 Citations Included

Quick Answer: What are Vitamin B12?

Vitamin B12 (cobalamin) is an essential water-soluble vitamin that your body cannot produce on its own[1][3]. It is naturally found in animal products and can be added to fortified foods or supplements. Your body needs B12 to make DNA, form red blood cells, support nervous system function, and convert food into energy[1][2][3].

Key Benefits

✓Forms red blood cells and prevents anemia[1][2]
✓Supports proper nervous system function and brain health[1][2]
✓Essential for DNA synthesis[1][2][3]
✓Helps convert food into energy[1]
✓Supports myelin synthesis for nerve protection[3]
✓May support bone density[8]
✓Aids protein metabolism[7]

Potential Side Effects

Vitamin B12 is water-soluble and excess amounts are typically excreted through urine. The search results do not provide detailed information on side effects or toxicity at this time.

Vitamin B12 Supplement Forms

Form	Administration Method	Notes
Oral supplements/tablets	Swallowed with water	Most common form; absorbed in small intestine
Gummies	Chewed orally	Convenient; palatability may improve compliance
Injections	Intramuscular injection	Used to treat deficiencies; bypasses absorption barriers[3]
Fortified foods	Consumed as part of diet	Found in cereals, nutritional yeast, fortified plant-based milks[1][2][6]

Scientific Consensus

Efficacy Profile

Vitamin B12 is scientifically established as essential for human health. It is needed to form red blood cells and DNA, and serves as a vital cofactor in metabolism[3]. B12 plays a critical role in the function and development of brain and nerve cells[2], and supports myelin synthesis in the nervous system[3]. For individuals with adequate B12 intake at the recommended dietary allowance of 2.4 micrograms daily for adults[4], the vitamin fulfills its essential metabolic functions. However, additional benefits beyond the recommended daily amount have not been demonstrated; exceeding the RDA does not provide added benefit[5].

Safety & Side Effects

Vitamin B12 is water-soluble, meaning excess amounts are excreted through urine rather than stored in the body[1]. The search results indicate that toxicity information exists but do not provide detailed side effect profiles at this time. B12 supplements are available in oral form, as part of fortified foods, and via intramuscular injection for treating deficiencies[3]. Most adults in the U.S. obtain sufficient B12 from their regular diet[5].

Dosage & Timing Protocols

The recommended dietary allowance (RDA) for vitamin B12 is 2.4 micrograms daily for most adults[4][5]. Higher amounts are recommended for pregnant and nursing women[4]. B12 is absorbed in the small intestine after combining with intrinsic factor protein in the stomach[1][2]. Those with absorption difficulties or following vegan/vegetarian diets may require supplements or fortified food sources to meet daily needs[5][6].

Common Questions

What is vitamin B12 and why is it important?

Vitamin B12 (cobalamin) is an essential water-soluble vitamin that your body cannot produce[1][3]. It is critical for making DNA, forming red blood cells, supporting nervous system function, and converting food into energy[1][2][3]. Your body requires B12 for proper metabolism and must obtain it from food or supplements[5].

Can my body make vitamin B12 on its own?

No. Your body cannot produce vitamin B12, so you must obtain it from external sources[1][5]. You can get B12 from animal-based foods, fortified foods, or supplements[1][6].

What are the best food sources of vitamin B12?

Natural sources include animal products such as fish, shellfish, meat, poultry, eggs, and dairy products[2][6]. The richest sources are beef liver, clams, and oysters[1][8]. Plant foods do not naturally contain B12, but fortified breakfast cereals and fortified nutritional yeast are readily available sources with high bioavailability[6].

Can vegetarians and vegans get enough B12 from food?

Vegetarians who consume dairy and eggs can get B12 from these products[1]. However, vegans cannot obtain B12 from plant foods unless they are fortified, such as certain breakfast cereals or plant-based milk substitutes[1][6]. Fortified nutritional yeast is also a vegan option[1][8]. Many vegans need to take supplements[8].

How much vitamin B12 do I need daily?

For most adults, the recommended dietary allowance (RDA) is 2.4 micrograms daily[4][5]. Higher amounts are recommended for pregnant and nursing women[4].

What are the signs of vitamin B12 deficiency?

A deficiency in B12 can lead to a specific type of anemia that causes weakness and fatigue[1]. The search results reference signs of deficiency but do not provide a comprehensive list at this time.

Who is at risk for B12 deficiency?

People at higher risk include those who do not eat animal products (vegans and strict vegetarians)[1][5], individuals with certain health conditions that affect absorption[1], pregnant or nursing women with inadequate intake[4], and those who lack the intrinsic factor protein needed to absorb B12[1].

How does my body absorb vitamin B12 from food?

When you consume foods containing B12, hydrochloric acid and enzymes in your stomach separate the vitamin from the protein it was bound to[1][2]. The B12 then combines with a protein called intrinsic factor, which your stomach produces[1][2]. This allows your body to absorb the B12 in the small intestine[2].

What happens if I cannot absorb B12 properly?

Some people lack the intrinsic factor protein needed for B12 absorption, which can result in deficiency[1]. These individuals may require B12 injections, which bypass the absorption process, to treat deficiencies[3].

What are the different forms of B12 supplements available?

Vitamin B12 is available in oral forms (tablets, gummies, liquids), as part of fortified foods (cereals, nutritional yeast, plant-based milks), and as intramuscular injections to treat deficiencies[3]. Oral supplements are most common, while injections are used specifically to address absorption problems[3].

Is it possible to take too much vitamin B12?

Vitamin B12 is water-soluble, meaning excess amounts are excreted through urine[1]. Taking more B12 than the recommended daily amount does not provide additional health benefits[5].

Why is B12 important for nerve health?

Vitamin B12 supports the function and development of brain and nerve cells[2]. It plays an essential role in myelin synthesis, which is the protective coating around nerve fibers[3]. This is why B12 is critical for maintaining a properly functioning nervous system[1].

How does B12 relate to energy levels?

Vitamin B12 helps your body convert food into energy[1] and plays a key role in metabolism and energy levels[5]. This is one reason why B12 deficiency can cause fatigue and weakness[1].

Is B12 found in plant-based foods?

Plant foods do not naturally contain B12[6][7]. However, some plant-based and fermented foods obtain B12 secondarily from symbiosis with bacteria or through bacterial fermentation (such as tempeh, nori, and seaweed)[3]. Additionally, many fortified plant-based products (cereals, nutritional yeast, soy/rice milk) contain added B12[1][2][6].

Does vitamin B12 support bone health?

Research indicates a connection between vitamin B12 levels and bone density. At least one study showed that adults with B12 deficiency have below-average bone density, with this finding being particularly common in women[8].

Can I get vitamin B12 from fortified foods instead of supplements?

Yes. Fortified breakfast cereals are readily available sources of B12 with high bioavailability[6] and can be a good source for vegetarians[7]. Fortified nutritional yeast and fortified plant-based milk substitutes also contain B12[1][2]. These options can help meet daily B12 needs without requiring supplements[5].

References & Citations

Disclaimer: This Fact Sheet was automatically generated based on available data sources. While we strive for accuracy, please verify claims independently. This content is for informational and entertainment purposes only and does not constitute medical advice. Always consult your doctor before starting any new supplement regimen.