Vitamin B12
B12 in food must first be released by stomach acid, then bind to intrinsic factor made in the stomach, before the end of the small intestine can absorb it.
Full ranking Dose tool Products (6,218)
Key facts
Sources: https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/ · FDA DV 2.4 mcg (https://www.fda.gov/food/nutrition-facts-label/daily-value-nutrition-and-supplement-facts-labels); pre-2016 DV [6] (https://www.federalregister.gov/documents/2016/05/27/2016-11867/food-labeling-revision-of-the-nutrition-and-supplement-facts-labels); no UL set
How it works: Why do some people absorb B12 poorly even when they take it?
- B12 in food is bound to protein; stomach acid and protease release it. B12 in supplements is free and skips this step.
- B12 binds to intrinsic factor, secreted by cells in the stomach wall.
- The complex is absorbed in the terminal ileum. People without intrinsic factor (pernicious anaemia) absorb very little.
- B12 is needed for red blood cell formation, nerve function and DNA synthesis.
Schematic only; positions and scale are not anatomical.
Sources: NIH ODS: VitaminB12 Fact Sheet for Health Professionals
Daily dose across products (mcg/day)
Label data from official national databases and brand websites, as declared; not lab-verified.
Common forms
| Form | Products | Median | P5–P95 | Elemental fraction |
|---|---|---|---|---|
| Methylcobalamin | 2689 | 100 mcg | 2.4 – 1,000 | — |
| Cyanocobalamin | 2535 | 25 mcg | 1.2 – 2,800 | — |
| Adenosylcobalamin | 157 | 225 mcg | 25 – 3,000 | — |
| Hydroxocobalamin | 34 | 125 mcg | 4 – 2,000 | — |
Common questions
What is the Daily Value for Vitamin B12?
The US FDA Daily Value for adults and children aged 4 and over is 2.4 mcg. It is a labelling reference, not a personal recommendation. [source]
How much Vitamin B12 do products usually contain per day?
As of 2026-11-01, 6,218 products list a comparable daily dose (6,558 dose records; one product can have several). The median is 50 mcg per day, and 90% of records fall between 1.2 and 2,000 mcg. Figures come from labels and are not lab-tested. [source]
Why do some people absorb B12 poorly even when they take it?
B12 in food must first be released by stomach acid, then bind to intrinsic factor made in the stomach, before the end of the small intestine can absorb it. No UL has been set. Long-term metformin or acid-reducing drugs can lower B12 absorption. [source]
What are the side effects of Vitamin B12?
Vitamin B12 has not been shown to cause harm, even at high doses. (Source: NIH ODS) [source]
What happens if you take too much Vitamin B12?
No UL has been set. Doses far above the recommended amount, such as 500 or 1,000 mcg, are considered safe; the body absorbs only a small share. (Source: NIH ODS) [source]
Is Vitamin B12 safe during pregnancy and breastfeeding?
The recommended amount is 2.6 mcg a day in pregnancy and 2.8 mcg while breastfeeding. Babies of pregnant or breastfeeding women who are strict vegetarians or vegans may also not get enough B12. (Source: NIH ODS) [source]
Does Vitamin B12 interact with medications or other supplements?
Acid reducers such as omeprazole and lansoprazole interfere with B12 absorption from food and can lead to deficiency. Metformin may reduce B12 absorption and blood levels. (Source: NIH ODS) [source]
How and when should you take Vitamin B12?
ODS says people over 50 should get most of their B12 from fortified foods or supplements, because many older adults lack the stomach acid to absorb B12 naturally present in food. Research has not shown any supplemental form (cyanocobalamin, methylcobalamin and others) to be better. (Source: NIH ODS) [source]
Top ranked
| Rank | Brand | Product | Per day | Score |
|---|---|---|---|---|
| 1 | Solgar | Vitamin B12 100 mcg | 100 mcg | 92.2 |
| 2 | BulkSupplements.com | Vitamin B12 1% (Methylcobalamin) | 200 mcg | 83.3 |
| 3 | BioCare | Nutrisorb Vitamin B12 | 50 mcg | 81.1 |
| 4 | 2158894 Ontario Inc. | B12 100 mcg | 100 mcg | 76.7 |
| 4 | 2158894 Ontario Inc. | B12 25 mcg | 25 mcg | 76.7 |