Vitamin B-12 deficiency

| Main Article
| Discussion
| Related Articles  [?]
| Bibliography  [?]
| External Links  [?]
| Citable Version  [?]

|
|
|
|
|
|
|
|

This editable Main Article is under development and subject to a disclaimer.

[edit intro]

In medicine, vitamin B-12 deficiency, is a "nutritional condition produced by a deficiency of Vitamin B-12 in the diet, characterized by megaloblastic anaemia. Since vitamin B 12 is not present in plants, humans have obtained their supply from animal products, from multivitamin supplements in the form of pills, and as additives to food preparations. A wide variety of neuropsychiatric abnormalities is also seen in vitamin B 12 deficiency and appears to be due to an undefined defect involving myelin synthesis."[1]

Manifestations include pernicious anaemia and subacute combined degeneration.

Vitamin B-12 deficiency may be combined with iron deficiency anaemia.[2]

## Diagnosis[edit]

Vitamin B-12 deficiency may be an explanation for macrocytosis[3]

However, the MCV is not completely accurate.[4][5][6]:

* Sensitivity: 60%[5], 64%[7] to 83%[6]
* Specificity: 70%[5]

B12 levels are helpful, but imperfect:

* Sensitivity: 95%[8][9]
* Specificity: 95%[10]

Folic acid levels may not help.[11]

Diagnosis may be especially difficult in alcoholics.[12]

### Treatment[edit]

Oral therapy may be effective.[13]

## References[edit]

1. ↑ Anonymous (2025), Vitamin B-12 deficiency (English). Medical Subject Headings. U.S. National Library of Medicine.
2. ↑ Beyan C, Kaptan K, Beyan E, Turan M (2005). "The platelet count/mean corpuscular hemoglobin ratio distinguishes combined iron and vitamin B12 deficiency from uncomplicated iron deficiency.". Int J Hematol 81 (4): 301-3. DOI:10.1532/IJH97.E0311. PMID 15914358. Research Blogging.
3. ↑ Wymer A, Becker DM (1990). "Recognition and evaluation of red blood cell macrocytosis in the primary care setting.". J Gen Intern Med 5 (3): 192-7. PMID 2341917. [e]
4. ↑ Oosterhuis WP, Niessen RW, Bossuyt PM, Sanders GT, Sturk A (2000). "Diagnostic value of the mean corpuscular volume in the detection of vitamin B12 deficiency.". Scand J Clin Lab Invest 60 (1): 9-18. PMID 10757449. [e]
5. ↑ 5.0 5.1 5.2 Seward SJ, Safran C, Marton KI, Robinson SH (1990). "Does the mean corpuscular volume help physicians evaluate hospitalized patients with anaemia?". J Gen Intern Med 5 (3): 187-91. DOI:10.1007/BF02600530. PMID 2187961. Research Blogging.
6. ↑ 6.0 6.1 Savage DG, Lindenbaum J, Stabler SP, Allen RH (1994). "Sensitivity of serum methylmalonic acid and total homocysteine determinations for diagnosing cobalamin and folate deficiencies.". Am J Med 96 (3): 239-46. PMID 8154512. [e]
7. ↑ Pruthi RK, Tefferi A (1994). "Pernicious anaemia revisited.". Mayo Clin Proc 69 (2): 144-50. PMID 8309266. [e]
8. ↑ Lindenbaum J, Savage DG, Stabler SP, Allen RH (1990). "Diagnosis of cobalamin deficiency: II. Relative sensitivities of serum cobalamin, methylmalonic acid, and total homocysteine concentrations.". Am J Hematol 34 (2): 99-107. PMID 2339684. [e]
9. ↑ Naurath HJ, Joosten E, Riezler R, Stabler SP, Allen RH, Lindenbaum J (1995). "Effects of vitamin B12, folate, and vitamin B6 supplements in elderly people with normal serum vitamin concentrations.". Lancet 346 (8967): 85-9. PMID 7603218. [e]
10. ↑ Matchar DB, McCrory DC, Millington DS, Feussner JR (1994). "Performance of the serum cobalamin assay for diagnosis of cobalamin deficiency.". Am J Med Sci 308 (5): 276-83. PMID 7977446. [e]
11. ↑ Ashraf MJ, Cook JR, Rothberg MB (2008). "Clinical utility of folic acid testing for patients with anaemia or dementia.". J Gen Intern Med 23 (6): 824-6. DOI:10.1007/s11606-008-0615-z. PMID 18414954. PMC PMC2517884. Research Blogging.
12. ↑ Savage D, Lindenbaum J (1986). "Anaemia in alcoholics.". Medicine (Baltimore) 65 (5): 322-38. PMID 3747828. [e]
13. ↑ Vidal-Alaball J, Butler CC, Cannings-John R, Goringe A, Hood K, McCaddon A et al. (2005). "Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency.". Cochrane Database Syst Rev (3): CD004655. DOI:10.1002/14651858.CD004655.pub2. PMID 16034940. Research Blogging. Review in: Evid Based Med. 2006 Feb;11(1):9