Vitamin B12

Vitamin B12
	General skeletal formula of cobalamins
	Stick model of cyanocobalamin (R = CN) based on the crystal structure
Clinical data
Other names	Vitamin B12, vitamin B-12, cobalamin
AHFS/Drugs.com	Monograph
MedlinePlus	a605007
License data	US DailyMed: Vitamin_b12;
Routes of; administration	By mouth, sublingual, intravenous (IV), intramuscular (IM), intranasal
ATC code	B03BA01 (WHO) ;
Legal status
Legal status	UK: OTC; US: OTC;
Pharmacokinetic data
Bioavailability	Readily absorbed in the distal half of the ileum.
Protein binding	Very high to specific transcobalamins plasma proteins.; Binding of hydroxocobalamin is slightly higher than cyanocobalamin.
Metabolism	Liver
Elimination half-life	Approximately 6 days; (400 days in the liver).
Excretion	Kidney
Identifiers
	IUPAC name α-(5,6-Dimethylbenzimidazolyl)cobamidcyanide;
CAS Number	68-19-9;
PubChem CID	184933;
DrugBank	DB00115;
ChemSpider	10469504;
UNII	P6YC3EG204;
KEGG	D00166;
ChEMBL	ChEMBL2110563;
Chemical and physical data
Formula	C63H88CoN14O14P
Molar mass	1355.388 g·mol−1
3D model (JSmol)	Interactive image;
	SMILES NC(=O)C[C@@]8(C)[C@H](CCC(N)=O)C=2/N=C8/C(/C)=C1/[C@@H](CCC(N)=O)[C@](C)(CC(N)=O)[C@@](C)(N1[Co+]C#N)[C@@H]7/N=C(C(\C)=C3/N=C(/C=2)C(C)(C)[C@@H]3CCC(N)=O)[C@](C)(CCC(=O)NCC(C)OP([O-])(=O)O[C@@H]6[C@@H](CO)O[C@H](n5cnc4cc(C)c(C)cc45)[C@@H]6O)[C@H]7CC(N)=O;
	InChI InChI=1S/C62H90N13O14P.CN.Co/c1-29-20-39-40(21-30(29)2)75(28-70-39)57-52(84)53(41(27-76)87-57)89-90(85,86)88-31(3)26-69-49(83)18-19-59(8)37(22-46(66)80)56-62(11)61(10,25-48(68)82)36(14-17-45(65)79)51(74-62)33(5)55-60(9,24-47(67)81)34(12-15-43(63)77)38(71-55)23-42-58(6,7)35(13-16-44(64)78)50(72–42)32(4)54(59)73–56;1–2;/h20-21,23,28,31,34-37,41,52-53,56-57,76,84H,12-19,22,24-27H2,1-11H3,(H15,63,64,65,66,67,68,69,71,72,73,74,77,78,79,80,81,82,83,85,86);;/q;;+2/p-2/t31?,34-,35-,36-,37+,41-,52-,53-,56-,57+,59-,60+,61+,62+;;/m1../s1 ; Key:RMRCNWBMXRMIRW-WYVZQNDMSA-L ;

Vitamin B₁₂, also known as cobalamin, is a water-soluble vitamin involved in metabolism.^[2] One of eight B vitamins, it serves as a vital cofactor in DNA synthesis and both fatty acid and amino acid metabolism.^[3] It plays an essential role in the nervous system by supporting myelin synthesis and is critical for the maturation of red blood cells in the bone marrow.^[2]^[4] While animals require B₁₂, plants do not, relying instead on alternative enzymatic pathways.^[5]

Vitamin B₁₂ is the most chemically complex of all vitamins,^[6]^[2]^[7] and is synthesized exclusively by certain archaea and bacteria.^[8] Natural food sources include meat, shellfish, liver, fish, poultry, eggs, and dairy products.^[2] It is also added to many breakfast cereals through food fortification and is available in dietary supplement and pharmaceutical forms.^[2] Supplements are commonly taken orally but may be administered via intramuscular injection to treat deficiencies.^[2]^[6]

Vitamin B₁₂ deficiency is prevalent worldwide, particularly among individuals with low or no intake of animal products, such as those following vegan or vegetarian diets, or those with low socioeconomic status.^[9] The most common cause in developed countries is impaired absorption due to loss of gastric intrinsic factor (IF), required for absorption.^[10] A related cause is reduced stomach acid production with age or from long-term use of proton-pump inhibitors,^[11] H₂ blockers, or other antacids.^[12]

Deficiency is especially harmful in pregnancy, childhood, and older adults. It can lead to neuropathy, megaloblastic anemia, and pernicious anemia,^[2]^[13] causing symptoms such as fatigue, paresthesia, cognitive decline, ataxia, and even irreversible nerve damage. In infants, untreated deficiency may result in neurological impairment and anemia.^[2] Maternal deficiency increases the risk of miscarriage, neural tube defects, and developmental delays in offspring.^[14] Folate levels may modify the presentation of symptoms and disease course.

^ Prieto T, Neuburger M, Spingler B, Zelder F (2016). "Inorganic Cyanide as Protecting Group in the Stereospecific Reconstitution of Vitamin B₁₂ from an Artificial Green Secocorrinoid" (PDF). Org. Lett. 18 (20): 5292–5295. doi:10.1021/acs.orglett.6b02611. PMID 27726382.
^ ^a ^b ^c ^d ^e ^f ^g ^h "Vitamin B12: Fact Sheet for Health Professionals". Office of Dietary Supplements, US National Institutes of Health. 26 March 2024. Retrieved 25 January 2025.
^ Yamada K (2013). "Cobalt: Its Role in Health and Disease". In Sigel A, Sigel H, Sigel RK (eds.). Interrelations between Essential Metal Ions and Human Diseases. Metal Ions in Life Sciences. Vol. 13. Springer. pp. 295–320. doi:10.1007/978-94-007-7500-8_9. ISBN 978-94-007-7499-5. PMID 24470095.
^ Cite error: The named reference Calderon2020 was invoked but never defined (see the help page).
^ Cite error: The named reference Smith2019 was invoked but never defined (see the help page).
^ ^a ^b "Vitamin B₁₂". Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis, OR. 4 June 2015. Archived from the original on 29 October 2019. Retrieved 5 April 2019.
^ Vincenti A, Bertuzzo L, Limitone A, D'Antona G, Cena H (June 2021). "Perspective: Practical Approach to Preventing Subclinical B12 Deficiency in Elderly Population". Nutrients. 13 (6): 1913. doi:10.3390/nu13061913. PMC 8226782. PMID 34199569.
^ Watanabe F, Bito T (January 2018). "Vitamin B12 sources and microbial interaction". Exp Biol Med (Maywood). 243 (2): 148–158. doi:10.1177/1535370217746612. PMC 5788147. PMID 29216732.
^ Obeid R, Heil SG, Verhoeven MM, van den Heuvel EG, de Groot LC, Eussen SJ (2019). "Vitamin B12 Intake From Animal Foods, Biomarkers, and Health Aspects". Front Nutr. 6: 93. doi:10.3389/fnut.2019.00093. PMC 6611390. PMID 31316992.
^ Cite error: The named reference PKIN2020VitB12 was invoked but never defined (see the help page).
^ Choudhury A, Jena A, Jearth V, Dutta AK, Makharia G, Dutta U, et al. (May 2023). "Vitamin B12 deficiency and use of proton pump inhibitors: a systematic review and meta-analysis". Expert Review of Gastroenterology & Hepatology. 17 (5): 479–487. doi:10.1080/17474124.2023.2204229. PMID 37060552.
^ "Acid-Reflux Drugs Tied to Lower Levels of Vitamin B-12". WebMD. Archived from the original on 23 July 2018. Retrieved 23 July 2018.
^ "Vitamin B12 Deficiency Anemia". www.hopkinsmedicine.org. 8 August 2021. Retrieved 16 February 2022.
^ Cite error: The named reference Finkelstein-2024 was invoked but never defined (see the help page).

[1] Prieto T, Neuburger M, Spingler B, Zelder F (2016). "Inorganic Cyanide as Protecting Group in the Stereospecific Reconstitution of Vitamin B₁₂ from an Artificial Green Secocorrinoid" (PDF). Org. Lett. 18 (20): 5292–5295. doi:10.1021/acs.orglett.6b02611. PMID 27726382.

[Ods-2] ^ ^a ^b ^c ^d ^e ^f ^g ^h "Vitamin B12: Fact Sheet for Health Professionals". Office of Dietary Supplements, US National Institutes of Health. 26 March 2024. Retrieved 25 January 2025.

[3] Yamada K (2013). "Cobalt: Its Role in Health and Disease". In Sigel A, Sigel H, Sigel RK (eds.). Interrelations between Essential Metal Ions and Human Diseases. Metal Ions in Life Sciences. Vol. 13. Springer. pp. 295–320. doi:10.1007/978-94-007-7500-8_9. ISBN 978-94-007-7499-5. PMID 24470095.

[Calderon2020-4] Cite error: The named reference Calderon2020 was invoked but never defined (see the help page).

[Smith2019-5] Cite error: The named reference Smith2019 was invoked but never defined (see the help page).

[lpi-6] "Vitamin B₁₂". Micronutrient Information Center, Linus Pauling Institute, Oregon State University, Corvallis, OR. 4 June 2015. Archived from the original on 29 October 2019. Retrieved 5 April 2019.

[Vincenti-7] Vincenti A, Bertuzzo L, Limitone A, D'Antona G, Cena H (June 2021). "Perspective: Practical Approach to Preventing Subclinical B12 Deficiency in Elderly Population". Nutrients. 13 (6): 1913. doi:10.3390/nu13061913. PMC 8226782. PMID 34199569.

[Watanabe-8] Watanabe F, Bito T (January 2018). "Vitamin B12 sources and microbial interaction". Exp Biol Med (Maywood). 243 (2): 148–158. doi:10.1177/1535370217746612. PMC 5788147. PMID 29216732.

[pmid31316992-9] Obeid R, Heil SG, Verhoeven MM, van den Heuvel EG, de Groot LC, Eussen SJ (2019). "Vitamin B12 Intake From Animal Foods, Biomarkers, and Health Aspects". Front Nutr. 6: 93. doi:10.3389/fnut.2019.00093. PMC 6611390. PMID 31316992.

[PKIN2020VitB12-10] Cite error: The named reference PKIN2020VitB12 was invoked but never defined (see the help page).

[Choudhury2023-11] Choudhury A, Jena A, Jearth V, Dutta AK, Makharia G, Dutta U, et al. (May 2023). "Vitamin B12 deficiency and use of proton pump inhibitors: a systematic review and meta-analysis". Expert Review of Gastroenterology & Hepatology. 17 (5): 479–487. doi:10.1080/17474124.2023.2204229. PMID 37060552.

[12] "Acid-Reflux Drugs Tied to Lower Levels of Vitamin B-12". WebMD. Archived from the original on 23 July 2018. Retrieved 23 July 2018.

[HopkinsMedicine-13] "Vitamin B12 Deficiency Anemia". www.hopkinsmedicine.org. 8 August 2021. Retrieved 16 February 2022.

[Finkelstein-2024-14] Cite error: The named reference Finkelstein-2024 was invoked but never defined (see the help page).

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