# Vitamin B12 (Cobalamin)

> Vitamin B12, or cobalamin, is crucial for red blood cell formation, nerve function, and DNA synthesis. It's vital for maintaining healthy nerve cells and t

*Source: [https://www.health3.app/biomarkers/vitaminb12](https://www.health3.app/biomarkers/vitaminb12)*

### On This Page

- What it measures
- Measurement units
- Reference ranges
- Health impact
- Related biomarkers
- Scientific references

## What is Vitamin B12 (Cobalamin)?

Vitamin B12, or cobalamin, is crucial for red blood cell formation, nerve function, and DNA synthesis. It's vital for maintaining healthy nerve cells and the myelin sheath, and it contributes to metabolism, fatty acid synthesis, and energy production. Holotranscobalamin (holoTC), the active part of B12, indicates bioavailability for cellular use. B12 deficiency can cause megaloblastic anemia, characterized by large, immature red blood cells, leading to fatigue and weakness. It can also lead to neurological issues like numbness, confusion, and poor memory. Insufficient B12 can stem from inadequate dietary intake, malabsorption disorders, or certain medications.

B12 absorption and utilization are affected by several factors. Folate deficiency can lead to functional **B12 deficiency**, while **high folate levels can mask B12 deficiency symptoms**. The intrinsic factor, produced in the stomach, is essential for B12 absorption, and its deficiency can lead to malabsorption later on in the small intestine. Conditions affecting intrinsic factor production, such as pernicious anemia or gastric surgery, can lead to B12 malabsorption and deficiency. In such cases, alternate ways of B12 intake, such as subcutaneous injections, may be necessary to avoid deficiency. Reduced gastric acid production, as in the elderly or from certain medications, can impair B12 absorption. H. pylori infection and chronic alcohol consumption can also reduce B12 levels.

B12 toxicity is rare, as it is water-soluble, and the body typically excretes excess amounts. **High B12 levels** might indicate liver disease, certain leukemias, or diabetes. For most people, managing B12 involves dietary intake or supplements, particularly for vegetarians, vegans, and those at risk of deficiency. In cases of malabsorption, B12 injections or high-dose oral supplements may be necessary.

**Factors that support healthy Vitamin B12 levels:**

- A balanced diet that includes B12-rich foods such as meat, fish, poultry, eggs, and dairy products supports healthy levels. Vegetarians and vegans may need to rely on fortified foods or B12 supplements to ensure adequate intake.
- People with a malabsorption disorder or at risk of B12 deficiency due to factors such as age, gastric surgery, or certain medications are usually advised to work with a healthcare provider to determine the appropriate form and dosage of B12 supplementation.
- There are potential interactions with other nutrients, such as **folate**, which can mask B12 deficiency symptoms. Adequate intake of both nutrients can come through a balanced diet or supplementation if necessary.
- When a B12 deficiency is suspected or symptoms like fatigue, weakness, or neurological issues occur, a healthcare provider can advise on proper diagnosis and treatment.
- Excessive alcohol consumption is best avoided, as these factors can contribute to reduced B12 levels.

## Measurement Units

Vitamin B12 (Cobalamin) can be measured in: ng/L, pg/100mL, pg/dL, pg/mL, pg%, pmol/L

## Reference Ranges by Age and Gender

Reference ranges represent typical values for healthy individuals. Your healthcare provider must interpret your specific results.

| Age Range | Gender | Unit | Optimal | Normal | Source |
| --- | --- | --- | --- | --- | --- |
| All ages | All genders | pg/mL | - | 200 - 800 | American, n.d. |

## Related Biomarkers

- [**Vitamin B9 (Folate) in Plasma**](https://www.health3.app/biomarkers/vitaminb9_plasma)

 Folate and vitamin B12 have a synergistic relationship, particularly in DNA synthesis and repair, and the metabolism of homocysteine. They depend on each other to and deficiency in either vitamin can lead to megaloblastic anemia and elevated homocysteine levels, increasing the risk of cardiovascular disease.[Scott, 1999][Stabler, 2013]
- [**Vitamin B9 (Folate) in RBC**](https://www.health3.app/biomarkers/vitaminb9_rbc)

 Folate and vitamin B12 have a synergistic relationship, particularly in DNA synthesis and repair, and the metabolism of homocysteine. They depend on each other to and deficiency in either vitamin can lead to megaloblastic anemia and elevated homocysteine levels, increasing the risk of cardiovascular disease.[Scott, 1999][Stabler, 2013]

## Related tools

- [**Vitamin B12 Level Reference Tool**](https://www.health3.app/tools/vitamin-b12-level-interpreter)
- [**Blood Test Unit Converter**](https://www.health3.app/tools/blood-test-unit-converter)

## Academic References

1. Kröger M, Mayer G, and Meier-Ewert K. Effects of vitamin B12 on performance and circadian rhythm in normal subjects (1996). *Neuropsychopharmacology*. [DOI: 10.1016/S0893-133X(96)00055-3](https://doi.org/10.1016/S0893-133X(96)00055-3)
2. Khattak N.N., Khan M.S., and Nawaz A.. Deficiency of vitamin B12 and its relation with neurological disorders: a critical review (2020). *The Journal of Basic and Applied Zoology*. [DOI: 10.1186/s41936-020-00148-0](https://doi.org/10.1186/s41936-020-00148-0)
3. American Board of Internal Medicine. ABIM Laboratory Test Reference Ranges - January. *American Board of Internal Medicine*. [View Source](https://www.abim.org/Media/bfijryql/laboratory-reference-ranges.pdf.)
4. Ames D, Carne R, Mander A, Moore E, Sanders K, and Watters D. Cognitive impairment and vitamin B12: a review (2012). *Int Psychogeriatr*. [DOI: 10.1017/S1041610211002511](https://doi.org/10.1017/S1041610211002511)
5. Vallet N. Megaloblastic anemia-related iron overload and erythroid regulators: a case report (2021). *J Med Case Reports*. [View Source](https://doi.org/10.1186/s13256-021-03065-0)
6. Heiner-Fokkema MR, van der Klauw MM, Wolffenbuttel BH, and Wouters HJCM. The Many Faces of Cobalamin (Vitamin B12) Deficiency (2019). *Mayo Clin Proc Innov Qual Outcomes*. [DOI: 10.1016/j.mayocpiqo.2019.03.002](https://doi.org/10.1016/j.mayocpiqo.2019.03.002)
7. Scott J.M.. Folate and vitamin B12 (1999). *Proceedings of the Nutrition Society*. [DOI: 10.1017/s0029665199000580](https://doi.org/10.1017/s0029665199000580)
8. Selhub J. Homocysteine metabolism (1999). *Annu Rev Nutr.*. [DOI: 10.1146/annurev.nutr.19.1.217](https://doi.org/10.1146/annurev.nutr.19.1.217)
9. Stabler S.P.. Vitamin B12 deficiency (2013). *New England Journal of Medicine*. [DOI: 10.1056/NEJMcp1113996](https://doi.org/10.1056/NEJMcp1113996)
10. Refsum H. and Smith A. D.. Homocysteine, B Vitamins, and Cognitive Impairment (2016). *Annual Review of Nutrition*. [DOI: 10.1146/annurev-nutr-071715-050947](https://doi.org/10.1146/annurev-nutr-071715-050947)
11. Beydoun HA, Beydoun MA, Canas JA, Gamaldo AA, McNeely JM, Shah MT, and Zonderman AB. Serum nutritional biomarkers and their associations with sleep among US adults in recent national surveys (2014). *PLoS One*. [DOI: 10.1371/journal.pone.0103490](https://doi.org/10.1371/journal.pone.0103490)
12. Mariën P, Clement F, De Deyn PP, Engelborghs S, Goeman J, Ketels V, Maertens K, Pickut BA, Saerens J, Somers N, Symons A, Vandevivere J, and Vloeberghs E. Correlations between cognitive behavioural and psychological findings and levels of vitamin B12 and folate in patients with dementia (2004). *Int J Geriatr Psychiatry*. [DOI: 10.1002/gps.1092](https://doi.org/10.1002/gps.1092)
13. Clarke R., McPartlin J., Nexø E., Scott J.M., Smith A. D., and Ueland P. M.. Facts and recommendations about total homocysteine determinations: an expert opinion (2006). *Clinical Chemistry*. [DOI: 10.1373/clinchem.2003.021634](https://doi.org/10.1373/clinchem.2003.021634)
14. van der Weyden MB. Red cell basic ferritin content of patients with megaloblastic anaemia due to vitamin B12 or folate deficiency (1984). *Scand J Haematol*. [View Source](https://doi.org/10.1111/j.1600-0609.1984.tb00710.x)
15. Köbe Theresa, Bohlken J, Flöel A, Grittner U, Hahn A, Pantel J, Rujescu D, Schnelle A, Schuchardt JP, Tesky VA, and Witte AV. Vitamin B-12 concentration memory performance and hippocampal structure in patients with mild cognitive impairment (2016). *Am J Clin Nutr*. [DOI: 10.3945/ajcn.115.116970](https://doi.org/10.3945/ajcn.115.116970)
16. Green R, Owen PJ, Ward M, and Wolffenbuttel BH. Vitamin B12 (2023). *BMJ*. [DOI: 10.1136/bmj-2022-071725](https://doi.org/10.1136/bmj-2022-071725)
17. Morris MS. The role of B vitamins in preventing and treating cognitive impairment and decline (2012). *Adv Nutr*. [DOI: 10.3945/an.112.002535](https://doi.org/10.3945/an.112.002535)

### ⚠️ Important Medical Information

This reference page is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Reference ranges vary between laboratories. Always review your lab results with a qualified healthcare provider.