Vitamin B12 (cobalamin) is a water-soluble vitamin essential for red blood cell formation, neurological function, and DNA synthesis. Research suggests that adequate B12 levels play a key role in maintaining healthy nerve cells and supporting cognitive function, while deficiency has been linked to megaloblastic anemia, fatigue, and neurological changes. Studies indicate that B12 contributes to the metabolism of homocysteine, an amino acid associated with cardiovascular risk when elevated, and emerging research has explored its potential role in mood regulation. Available in several supplemental forms — including cyanocobalamin, methylcobalamin, hydroxocobalamin, and adenosylcobalamin — B12 is naturally found in animal-based foods, making it a nutrient of particular interest for older adults and those following plant-based diets who may have limited dietary intake or reduced absorption capacity.
Compare this supplementResearch suggests that vitamin B12 deficiency is a well-established cause of macrocytic and megaloblastic anemia, as ...
View studies →Research suggests that the relationship between vitamin B12 and cognitive function is modest and context-dependent, w...
View studies →Research suggests a complex and somewhat inconsistent picture regarding vitamin B12 and mood support. A 2006 narrativ...
View studies →Research suggests that vitamin B12 plays a role in energy metabolism and that deficiency may contribute to fatigue, w...
View studies →Research suggests that the available studies linked here do not directly investigate vitamin B12 as an intervention f...
View studies →Research suggests that the available published evidence linking vitamin B12 directly to nerve function is limited wit...
View studies →Very high-dose vitamin C may reduce vitamin B12 absorption.
View details →B12 and folate work together in the methylation cycle and red blood cell formation.
View details →These are commonly referenced dosage ranges for this supplement. They are not medical recommendations. Always consult a healthcare provider before supplementing.
| Form | Dose range | Frequency | Studied for | Source |
|---|---|---|---|---|
| Liquid | 1,000 mcg | Weekly | Intramuscular or sublingual B12 for severe deficiency and nerve function recovery | Standard clinical protocol for intramuscular injection; sublingual liquid at equivalent dose studied in RCTs |
| Tablet | 500–1,000 mcg | Daily | Cognitive function and nerve function support in older adults | Widely used in RCTs examining cognitive decline and neuropathy in elderly populations |
| Tablet | 2.4 mcg | Daily | General health and dietary adequacy in healthy adults | Based on RDA established by Institute of Medicine for adults |
| Tablet | 400–1,000 mcg | Daily | Mood support and energy and fatigue reduction | Doses used in combination B-vitamin trials targeting fatigue and mood outcomes |
| Tablet | 1,000–2,000 mcg | Daily | Pernicious anemia and malabsorption-related deficiency | High-dose oral B12 shown effective as alternative to injections in clinical trials |
| Tablet | 1,000 mcg | Daily | Vitamin B12 deficiency treatment and homocysteine reduction | Common in clinical trials for deficiency correction and cardiovascular risk markers |