Vitamin B12
Needed for healthy nerves, DNA, and red blood cell formation.
Why it matters
Vitamin B12 helps form red blood cells, supports nerve function, and is required for DNA production.
- Supports red blood cell formation.
- Helps maintain nerve function.
- Required for DNA synthesis.
If intake is too low
Vitamin B12 deficiency can cause megaloblastic anemia and neurologic problems. If it goes untreated, numbness, balance trouble, and memory changes can become long-lasting or permanent.
- Fatigue and weakness from megaloblastic anemia.
- Numbness, tingling, or balance problems.
- Memory or mood changes when deficiency is prolonged.
If intake is too high
No upper limit has been established for vitamin B12 because harmful effects from high intake have not been confirmed in healthy people.
- No established upper limit.
- No clear toxicity pattern from food or supplements in healthy people.
- Persistent symptoms are more likely to reflect deficiency or another condition than excess B12.
No adult upper limit established
No tolerable upper intake level has been established because vitamin B12 has not been shown to cause harm at high intakes in healthy people.
Common food sources
Vitamin B12 naturally comes from animal foods, while fortified foods and supplements matter more for people who eat little or no animal products.
- Fish, meat, poultry, eggs, and dairy foods
- Fortified breakfast cereals and plant milks
- Fortified nutritional yeast and supplements
Who may need closer attention
Low B12 often has more to do with absorption than raw intake, especially with age and some medications.
- Older adults
- Vegans and some vegetarians without reliable fortified foods or supplements
- People using metformin, proton pump inhibitors, or H2 blockers, or those with pernicious anemia or intestinal surgery history
Use extra caution if
Small details change the risk picture with nutrients more than most people expect.
You are an older adult, eat a vegan diet without fortified foods or supplements, use metformin or acid-suppressing medicines, or have a digestive disorder that affects absorption.
Supplement and label notes
Useful context when this nutrient shows up across more than one product.
- Common label forms include cyanocobalamin and methylcobalamin.
- For many people, whether B12 is absorbed consistently matters more than which form sounds more premium.
- If your diet is plant-based, fortified foods and supplements usually matter more than trying to find trace amounts in unfortified foods.
Daily Value targets in SuppMap
These are the same label-style Daily Value targets used in the app.
Official references
These pages were used to draft the summaries on this guide.
Educational only. These pages are not a diagnosis or a substitute for personal medical care.
More guides
Keep moving through the rest of the Daily Value chart from here.