Vitamin B12 deficiency

Devalia V, Hamilton MS, Molloy AM; British Committee for Standards in Haematology. Guidelines for the diagnosis and treatment of cobalamin and folate disorders. Br J Haematol. 2014 Aug;166(4):496-513.Full text  Abstract

Snow CF. Laboratory diagnosis of vitamin B12 and folate deficiency: a guide for the primary care physician. Arch Intern Med. 1999 Jun 28;159(12):1289-98.Full text  Abstract

Stabler SP. Clinical practice. Vitamin B12 deficiency. N Engl J Med. 2013 Jan 10;368(2):149-60. Abstract

National Institutes of Health, Office of Dietary Supplements. Vitamin B12: fact sheet for health professionals. Mar 2024 [internet publication].Full text

Guidelines and Protocols Advisory Committee, British Columbia. Cobalamin (vitamin B12) and folate deficiency. Apr 2023 [internet publication].​Full text

1. Devalia V, Hamilton MS, Molloy AM; British Committee for Standards in Haematology. Guidelines for the diagnosis and treatment of cobalamin and folate disorders. Br J Haematol. 2014 Aug;166(4):496-513.Full text  Abstract

2. Snow CF. Laboratory diagnosis of vitamin B12 and folate deficiency: a guide for the primary care physician. Arch Intern Med. 1999 Jun 28;159(12):1289-98.Full text  Abstract

3. Tavares J, Baptista B, Gonçalves B, et al. Pernicious anaemia with normal vitamin B12. Eur J Case Rep Intern Med. 2019;6(2):001045.Full text  Abstract

4. Shah DR, Daver N, Borthakur G, et al. Pernicious anemia with spuriously normal vitamin B12 level might be misdiagnosed as myelodysplastic syndrome. Clin Lymphoma Myeloma Leuk. 2014 Aug;14(4):e141-3. Abstract

5. Yang DT, Cook RJ. Spurious elevations of vitamin B12 with pernicious anemia. N Engl J Med. 2012 May 3;366(18):1742-3.Full text  Abstract

6. Mazokopakis EE. Normal serum cobalamin levels do not exclude the diagnosis of pernicious anaemia: a case report. Fam Pract. 2020 Feb 19;37(1):1-3.Full text  Abstract

7. Wang Z, Zhu W, Xing Y, et al. B vitamins and prevention of cognitive decline and incident dementia: a systematic review and meta-analysis. Nutr Rev. 2022 Mar 10;80(4):931-49.Full text  Abstract

8. Chen H, Liu S, Ge B, et al. Effects of folic acid and vitamin B12 supplementation on cognitive impairment and inflammation in patients with Alzheimer's disease: a randomized, single-blinded, placebo-controlled trial. J Prev Alzheimers Dis. 2021;8(3):249-56. Abstract

9. Gil Martínez V, Avedillo Salas A, Santander Ballestín S. Vitamin supplementation and dementia: a systematic review. Nutrients. 2022 Feb 28;14(5):1033.Full text  Abstract

10. Tucker KL, Rich S, Rosenberg I, et al. Plasma vitamin B-12 concentrations relate to intake source in the Framingham Offspring study. Am J Clin Nutr. 2000 Feb;71(2):514-22. Abstract

11. Sukumar N, Saravanan P. Investigating vitamin B12 deficiency. BMJ. 2019 May 10;365:l1865. Abstract

12. Pennypacker LC, Allen RH, Kelly JP, et al. High prevalence of cobalamin deficiency in elderly outpatients. J Am Geriatr Soc. 1992 Dec;40(12):1197-204. Abstract

13. Clarke R, Grimley Evans J, Schneede J, et al. Vitamin B12 and folate deficiency in later life. Age Ageing. 2004 Jan;33(1):34-41.Full text  Abstract

14. Andres E, Loukili NH, Noel E, et al. Vitamin B12 (cobalamin) deficiency in elderly patients. CMAJ. 2004 Aug 3;171(3):251-9.Full text  Abstract

15. Pfisterer KJ, Sharratt MT, Heckman GG, et al. Vitamin B12 status in older adults living in Ontario long-term care homes: prevalence and incidence of deficiency with supplementation as a protective factor. Appl Physiol Nutr Metab. 2016 Feb;41(2):219-22. Abstract

16. Wong CW, Ip CY, Leung CP, et al. Vitamin B12 deficiency in the institutionalized elderly: A regional study. Exp Gerontol. 2015 Sep;69:221-5. Abstract

17. Mineva EM, Sternberg MR, Bailey RL, et al. Fewer US adults had low or transitional vitamin B12 status based on the novel combined indicator of vitamin B12 status compared with individual, conventional markers, NHANES 1999-2004. Am J Clin Nutr. 2021 Sep 1;114(3):1070-79.Full text  Abstract

18. Hunt A, Harrington D, Robinson S. Vitamin B12 deficiency. BMJ. 2014 Sep 4;349:g5226. Abstract

19. Allen LH. How common is vitamin B-12 deficiency? Am J Clin Nutr. 2009 Feb;89(2):693S-6S.Full text  Abstract

20. Björkegren K, Svärdsudd K. Serum cobalamin, folate, methylmalonic acid and total homocysteine as vitamin B12 and folate tissue deficiency markers amongst elderly Swedes - a population-based study. J Intern Med. 2001 May;249(5):423-32.Full text  Abstract

21. Yajnik CS, Deshpande SS, Lubree HG, et al. Vitamin B12 deficiency and hyperhomocysteinemia in rural and urban Indians. J Assoc Physicians India. 2006 Oct;54:775-82. Abstract

22. Fakhrzadeh H, Ghotbi S, Pourebrahim R, et al. Total plasma homocysteine, folate, and vitamin B12 status in healthy Iranian adults: the Tehran homocysteine survey (2003-2004)/a cross-sectional population based study. BMC Public Health. 2006 Feb 13;6:29.Full text  Abstract

23. Loikas S, Koskinen P, Irjala K, et al. Vitamin B12 deficiency in the aged: a population-based study. Age Ageing. 2007 Mar;36(2):177-83.Full text  Abstract

24. Madhari RS, Boddula S, Ravindranadh P, et al. High dietary micronutrient inadequacy in peri-urban school children from a district in South India: Potential for staple food fortification and nutrient supplementation. Matern Child Nutr. 2020 Dec;16 Suppl 3:e13065.Full text  Abstract

25. Pawlak R, Parrott SJ, Raj S, et al. How prevalent is vitamin B(12) deficiency among vegetarians? Nutr Rev. 2013 Feb;71(2):110-7.Full text  Abstract

26. Herrmann W, Schorr H, Obeid R, et al. Vitamin B-12 status, particularly holotranscobalamin II and methylmalonic acid concentrations, and hyperhomocysteinemia in vegetarians. Am J Clin Nutr. 2003 Jul;78(1):131-6. Abstract

27. Weng TC, Chang CH, Dong YH, et al. Anaemia and related nutrient deficiencies after Roux-en-Y gastric bypass surgery: a systematic review and meta-analysis. BMJ Open. 2015 Jul 16;5(7):e006964.Full text  Abstract

28. Schijns W, Homan J, van der Meer L, et al. Efficacy of oral compared with intramuscular vitamin B-12 supplementation after Roux-en-Y gastric bypass: a randomized controlled trial. Am J Clin Nutr. 2018 Jul 1;108(1):6-12.Full text  Abstract

29. Rashid S, Meier V, Patrick H. Review of vitamin B12 deficiency in pregnancy: a diagnosis not to miss as veganism and vegetarianism become more prevalent. Eur J Haematol. 2021 Apr;106(4):450-5.Full text  Abstract

30. Sukumar N, Rafnsson SB, Kandala NB, et al. Prevalence of vitamin B-12 insufficiency during pregnancy and its effect on offspring birth weight: a systematic review and meta-analysis. Am J Clin Nutr. 2016 May;103(5):1232-51.Full text  Abstract

31. Jung SB, Nagaraja V, Kapur A, et al. Association between vitamin B12 deficiency and long-term use of acid-lowering agents: a systematic review and meta-analysis. Intern Med J. 2015 Apr;45(4):409-16. Abstract

32. Chapman LE, Darling AL, Brown JE, et al. Association between metformin and vitamin B12 deficiency in patients with type 2 diabetes: a systematic review and meta-analysis. Diabetes Metab. 2016 Nov;42(5):316-27. Abstract

33. Marino MC, de Olivera CA, Rocha AM, et al. Long-term effect of Helicobacter pylori eradication on plasma homocysteine in elderly patients with cobalamin deficiency. Gut. 2007 Apr;56(4):469-74.Full text  Abstract

34. Kaptan K, Beyan C, Ural AU, et al. Helicobacter pylori - is it a novel causative agent in vitamin B12 deficiency? Arch Intern Med. 2000 May 8;160(9):1349-53. Abstract

35. Cellini M, Santaguida MG, Virili C, et al. Hashimoto's thyroiditis and autoimmune gastritis. Front Endocrinol (Lausanne). 2017;8:92.Full text  Abstract

36. Allakky A. Exploring the association of helicobacter pylori with anti-intrinsic factor and anti-parietal cell antibodies in pernicious anemia: a systematic review. Cureus. 2023 Sep;15(9):e45887.Full text  Abstract

37. Ayesh MH, Jadalah K, Al Awadi E, et al. Association between vitamin B12 level and anti-parietal cells and anti-intrinsic factor antibodies among adult Jordanian patients with Helicobacter pylori infection. Braz J Infect Dis. 2013 Nov-Dec;17(6):629-32.Full text  Abstract

38. Gowdappa HB, Mahesh M, Murthy KV, et al. Helicobacter pylori associated vitamin B12 deficiency, pernicious anaemia and subacute combined degeneration of the spinal cord. BMJ Case Rep. 2013 Sep 30;2013:bcr2013200380.Full text  Abstract

39. Serin E, Gümürdülü Y, Ozer B, et al. Impact of Helicobacter pylori on the development of vitamin B12 deficiency in the absence of gastric atrophy. Helicobacter. 2002 Dec;7(6):337-41. Abstract

40. Osmola M, Chapelle N, Vibet MA, et al. Iron and vitamin B12 deficiency in patients with autoimmune gastritis and helicobacter pylori gastritis: results from a prospective multicenter study. Dig Dis. 2024;42(2):145-53. Abstract

41. Lewerin C, Jacobsson S, Lindstedt G, et al. Serum biomarkers for atrophic gastritis and antibodies against Helicobacter pylori in the elderly: implications for vitamin B12, folic acid and iron status and response to oral vitamin therapy. Scand J Gastroenterol. 2008;43(9):1050-6. Abstract

42. Afsar MNA, Jhinu ZN, Bhuiyan MAI, et al. Helicobacter pylori infection and micronutrient deficiency in pregnant women: a systematic review and meta-analysis. BMJ Open Gastroenterol. 2020 Oct;7(1):e000490.Full text  Abstract

43. Aslan K, Bozdemir H, Unsal C, et al. The effect of anticonvulsant drugs on vitamin B12 metabolism. Int J Lab Hematol. 2008 Feb;30(1):26-35. Abstract

44. Linnebank M, Moskau S, Semmler A, et al. Antiepileptic drugs interact with folate and vitamin B12 serum levels. Ann Neurol. 2011 Feb;69(2):352-9.Full text  Abstract

45. Paulus MC, Wijnhoven AM, Maessen GC, et al. Does vitamin B12 deficiency explain psychiatric symptoms in recreational nitrous oxide users? A narrative review. Clin Toxicol (Phila). 2021 Nov;59(11):947-55.Full text  Abstract

46. Oussalah A, Julien M, Levy J, et al. Global burden related to nitrous oxide exposure in medical and recreational settings: a systematic review and individual patient data meta-analysis. J Clin Med. 2019 Apr 23;8(4):551.Full text  Abstract

47. van Amsterdam JG, Nabben T, van den Brink W. Increasing recreational nitrous oxide use: should we worry? A narrative review. J Psychopharmacol. 2022 Aug;36(8):943-50. Abstract

48. Andersen KJ, von der Lippe G. The effect of proteolytic enzymes on the vitamin B12-binding proteins of human gastric juice and saliva. Scand J Gastroenterol. 1979;14(7):833-8. Abstract

49. Stabler SP. Clinical practice. Vitamin B12 deficiency. N Engl J Med. 2013 Jan 10;368(2):149-60. Abstract

50. Sahu P, Thippeswamy H, Chaturvedi SK. Neuropsychiatric manifestations in vitamin B12 deficiency. Vitam Horm. 2022;119:457-70.Full text  Abstract

51. Arias PM, Domeniconi EA, García M, et al. Micronutrient deficiencies after Roux-en-Y gastric bypass: long-term results. Obes Surg. 2020 Jan;30(1):169-73.Full text  Abstract

52. Shankar P, Boylan M, Sriram K. Micronutrient deficiencies after bariatric surgery. Nutrition. 2010 Nov-Dec;26(11-12):1031-7. Abstract

53. Thompson WG, Wrathell E. The relation between ileal resection and vitamin B12 absorption. Can J Surg. 1977 Sep;20(5):461-4. Abstract

54. Duerksen DR, Fallows G, Bernstein CN. Vitamin B12 malabsorption in patients with limited ileal resection. Nutrition. 2006 Nov-Dec;22(11-12):1210-3. Abstract

55. Pironi L, Cuerda C, Jeppesen PB, et al. ESPEN guideline on chronic intestinal failure in adults - update 2023. Clin Nutr. 2023 Oct;42(10):1940-2021.Full text  Abstract

56. Valvano M, Capannolo A, Cesaro N, et al. Nutrition, nutritional status, micronutrients deficiency, and disease course of inflammatory bowel disease. Nutrients. 2023 Aug 31;15(17):3824.Full text  Abstract

57. Lederer AK, Hannibal L, Hettich M, et al. Vitamin B12 status upon short-term intervention with a vegan diet-a randomized controlled trial in healthy participants. Nutrients. 2019 Nov 18;11(11):2815.Full text  Abstract

58. Aroda VR, Edelstein SL, Goldberg RB, et al. Long-term metformin use and vitamin b12 deficiency in the diabetes prevention program outcomes study. J Clin Endocrinol Metab. 2016 Apr;101(4):1754-61.Full text  Abstract

59. Mazokopakis EE, Starakis IK. Recommendations for diagnosis and management of metformin-induced vitamin B12 (Cbl) deficiency. Diabetes Res Clin Pract. 2012 Sep;97(3):359-67. Abstract

60. Yang W, Cai X, Wu H, et al. Associations between metformin use and vitamin B12 levels, anemia, and neuropathy in patients with diabetes: a meta-analysis. J Diabetes. 2019 Sep;11(9):729-43. Abstract

61. National Institute for Health and Care Excellence. ​Vitamin B12 deficiency in over 16s: diagnosis and management. Mar 2024 [internet publication].Full text

62. de Jager J, Kooy A, Lehert P, et al. Long term treatment with metformin in patients with type 2 diabetes and risk of vitamin B-12 deficiency: randomised placebo controlled trial. BMJ. 2010 May 20;340:c2181.Full text  Abstract

63. Jung C, Park S, Kim H. Concomitant use of metformin and proton pump inhibitors increases vitamin B12 deficiency risk in type 2 diabetes. J Diabetes Investig. 2025 Apr 4.Full text  Abstract

64. Ito T, Ramos-Alvarez I, Jensen RT. Long-term proton pump inhibitor-acid suppressive treatment can cause vitamin B(12) deficiency in Zollinger-Ellison Syndrome (ZES) patients. Int J Mol Sci. 2024 Jul 2;25(13):7286.Full text  Abstract

65. Choudhury A, Jena A, Jearth V, et al. Vitamin B12 deficiency and use of proton pump inhibitors: a systematic review and meta-analysis. Expert Rev Gastroenterol Hepatol. 2023 May;17(5):479-87. Abstract

66. Lam JR, Schneider JL, Zhao W, et al. Proton pump inhibitor and histamine 2 receptor antagonist use and vitamin B12 deficiency. JAMA. 2013 Dec 11;310(22):2435-42.Full text  Abstract

67. Adam LC, Grobelny A, Hahn K, et al. Severe subacute combined degeneration of the spinal cord resulting from nitrous oxide (N2O) abuse: a case series. Neurol Res Pract. 2025 Feb 13;7(1):7.Full text  Abstract

68. Pflipsen MC, Oh RC, Saguil A, et al. The prevalence of vitamin B12 deficiency in patients with type 2 diabetes mellitus: a cross-sectional study. J Am Board Fam Med. 2009 Sep-Oct;22(5):528-34.Full text  Abstract

69. Kim J, Ahn CW, Fang S, et al. Association between metformin dose and vitamin B12 deficiency in patients with type 2 diabetes. Medicine (Baltimore). 2019 Nov;98(46):e17918.Full text  Abstract

70. Finkelstein JL, Kurpad AV, Thomas T, et al. Vitamin B12 status in pregnant women and their infants in South India. Eur J Clin Nutr. 2017 Sep 12;71(9):1046-53. Abstract

71. Rogne T, Tielemans MJ, Chong MF, et al. Associations of maternal vitamin B12 concentration in pregnancy with the risks of preterm birth and low birth weight: a systematic review and meta-analysis of individual participant data. Am J Epidemiol. 2017 Feb 1;185(3):212-23.Full text  Abstract

72. National Institutes of Health, Office of Dietary Supplements. Vitamin B12: fact sheet for health professionals. Mar 2024 [internet publication].Full text

73. Berger MM, Shenkin A, Schweinlin A, et al. ​ESPEN micronutrient guideline. Clin Nutr. 2022;41:1357-424.Full text

74. Das JK, Salam RA, Mahmood SB, et al. Food fortification with multiple micronutrients: impact on health outcomes in general population. Cochrane Database Syst Rev. 2019 Dec 18;12:CD011400.Full text  Abstract

75. World Health Organization. WHO fortification of wheat flour with vitamins and minerals as a public health strategy. 2022 [internet publication].Full text

76. Miller JW, Smith A, Troen AM, et al. Excess folic acid and vitamin B12 deficiency: clinical implications? Food Nutr Bull. 2024 Jun;45(1_suppl):S67-72.Full text  Abstract

77. Ismail S, Eljazzar S, Ganji V. Intended and unintended benefits of folic acid fortification-a narrative review. Foods. 2023 Apr 11;12(8):1612.Full text  Abstract

78. Moore M, Hopkins J, Wainwright P. Primary care management of patients after weight loss surgery. BMJ. 2016 Mar 10;352:i945.Full text  Abstract

79. Vasconcelos OM, Poehm EH, McCarter RJ, et al. Potential outcome factors in subacute combined degeneration: review of observational studies. J Gen Intern Med. 2006 Oct;21(10):1063-8.Full text  Abstract

80. Wolffenbuttel BH, Owen PJ, Ward M, et al. Vitamin B(12). BMJ. 2023 Nov 20;383:e071725.Full text

81. Guidelines and Protocols Advisory Committee, British Columbia. Cobalamin (vitamin B12) and folate deficiency. Apr 2023 [internet publication].​Full text

82. Mousavi T, Jalali H, Moosazadeh M. Hematological parameters in patients with recurrent Aphthous Stomatitis: a systematic review and meta-analysis. BMC Oral Health. 2024 Mar 16;24(1):339.Full text  Abstract

83. Hoey L, Strain JJ, McNulty H. Studies of biomarker responses to intervention with vitamin B-12: a systematic review of randomized controlled trials. Am J Clin Nutr. 2009 Jun;89(6):1981S-96S.Full text  Abstract

84. Savage DG, Lindenbaum J, Stabler SP, et al. Sensitivity of serum methylmalonic acid and total homocysteine determinations for diagnosing cobalamin and folate deficiencies. Am J Med. 1994 Mar;96(3):239-46. Abstract

85. National Institute for Health and Care Excellence. Active B12 assay for diagnosing vitamin B12 deficiency. Sep 2015 [internet publication].Full text

86. Miller JW, Garrod MG, Rockwood AL, et al. Measurement of total vitamin B12 and holotranscobalamin, singly and in combination, in screening for metabolic vitamin B12 deficiency. Clin Chem. 2006 Feb;52(2):278-85.Full text  Abstract

87. Obeid R, Herrmann W. Holotranscobalamin in laboratory diagnosis of cobalamin deficiency compared to total cobalamin and methylmalonic acid. Clin Chem Lab Med. 2007;45(12):1746-50. Abstract

88. Valente E, Scott JM, Ueland PM, et al. Diagnostic accuracy of holotranscobalamin, methylmalonic acid, serum cobalamin, and other indicators of tissue vitamin b12 status in the elderly. Clin Chem. 2011 Jun;57(6):856-63.Full text  Abstract

89. Muckerheide M. Therapeutic doses of vitamin B12 give false-positive values for intrinsic-factor-blocking antibodies. Clin Chem. 1984 Sep;30(9):1579. Abstract

90. Stenman UH. False-positive tests for intrinsic-factor antibody. Lancet. 1976 Aug 21;2(7982):428. Abstract

91. Rusak E, Chobot A, Krzywicka A, et al. Anti-parietal cell antibodies - diagnostic significance. Adv Med Sci. 2016 Sep;61(2):175-9. Abstract

92. Slingerland DW, Cardarelli JA, Burrows BA, et al. The utility of serum gastrin levels in assessing the significance of low serum vitamin B12 levels. Arch Intern Med. 1984 Jun;144(6):1167-8. Abstract

93. Simundic AM, Bölenius K, Cadamuro J, et al. Joint EFLM-COLABIOCLI recommendation for venous blood sampling. Clin Chem Lab Med 2018;56(12):2015-38. Abstract

94. Mechanick JI, Apovian C, Brethauer S, et al; American Association of Clinical Endocrinologists; Obesity Society; American Society for Metabolic & Bariatric Surgery. Clinical practice guidelines for the perioperative nutritional, metabolic, and nonsurgical support of the bariatric surgery patient - 2019 update. Endocr Pract. 2019 Dec;25(12):1346-59.Full text  Abstract

95. Lindenbaum J, Healton EB, Savage DG, et al. Neuropsychiatric disorders caused by cobalamin deficiency in the absence of anemia or macrocytosis. N Engl J Med. 1988 Jun 30;318(26):1720-8. Abstract

96. American Psychiatric Association. Diagnostic and statistical manual of mental disorders, 5th ed., text revision (DSM-5-TR). Washington, DC: American Psychiatric Publishing; 2022.

97. Centers for Disease Control and Prevention. Laboratory testing for the diagnosis of HIV infection: updated recommendations. June 2014 [internet publication].Full text

98. Hsing AW, Hansson LE, McLaughlin JK, et al. Pernicious anemia and subsequent cancer: a population-based cohort study. Cancer. 1993 Feb 1;71(3):745-50. Abstract

99. Sanz-Cuesta T, Escortell-Mayor E, Cura-Gonzalez I, et al. Oral versus intramuscular administration of vitamin B12 for vitamin B12 deficiency in primary care: a pragmatic, randomised, non-inferiority clinical trial (OB12). BMJ Open. 2020 Aug 20;10(8):e033687.Full text  Abstract

100. Kuzminski AM, Del Giacco EJ, Allen RH, et al. Effective treatment of cobalamin deficiency with oral cobalamin. Blood. 1998 Aug 15;92(4):1191-8.Full text  Abstract

101. Berlin H, Berlin R, Brante G. Oral treatment of pernicious anemia with high doses of vitamin B12 without intrinsic factor. Acta Med Scand. 1968 Oct;184(4):247-58. Abstract

102. Gomollón F, Gargallo CJ, Muñoz JF, et al. Oral cyanocobalamin is effective in the treatment of vitamin B12 deficiency in Crohn's disease. Nutrients. 2017 Mar 20;9(3):E308.Full text  Abstract

103. Wang H, Li L, Qin LL, et al. Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency. Cochrane Database Syst Rev. 2018 Mar 15;(3):CD004655.Full text  Abstract

104. Tillemans MPH, Giezen TJ, Egberts TCG, et al. Intranasal vitamin B(12) administration in elderly patients: a randomized controlled comparison of two dosage regimens. Br J Clin Pharmacol. 2024 Aug;90(8):1975-83.Full text  Abstract

105. Sharabi A, Cohen E, Sulkes J, et al. Replacement therapy for vitamin B12 deficiency: comparison between the sublingual and oral route. Br J Clin Pharmacol. 2003 Dec;56(6):635-8.Full text  Abstract

106. Slot WB, Merkus FW, Van Deventer SJ, et al. Normalization of plasma vitamin B12 concentration by intranasal hydroxocobalamin in vitamin B12-deficient patients. Gastroenterology. 1997 Aug;113(2):430-3. Abstract

107. Parry-Strong A, Langdana F, Haeusler S, et al. Sublingual vitamin B12 compared to intramuscular injection in patients with type 2 diabetes treated with metformin: a randomised trial. N Z Med J. 2016 Jun 10;129(1436):67-75. Abstract

108. Carmel R. How I treat cobalamin (vitamin B12) deficiency. Blood. 2008 Sep 15;112(6):2214-21.Full text  Abstract

109. Butler CC, Vidal-Alaball J, Cannings-John R, et al. Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency: a systematic review of randomized controlled trials. Fam Pract. 2006 Jun;23(3):279-85.Full text  Abstract

110. Jatoi S, Hafeez A, Riaz SU, et al. Low vitamin B12 levels: an underestimated cause of minimal cognitive impairment and dementia. Cureus. 2020 Feb 13;12(2):e6976.Full text  Abstract

111. Del Bo' C, Riso P, Gardana C, et al. Effect of two different sublingual dosages of vitamin B12 on cobalamin nutritional status in vegans and vegetarians with a marginal deficiency: A randomized controlled trial. Clin Nutr. 2019 Apr;38(2):575-583.Full text  Abstract

112. Hashash JG, Elkins J, Lewis JD, et al. AGA Clinical practice update on diet and nutritional therapies in patients with inflammatory bowel disease: expert review. Gastroenterology. 2024 Mar;166(3):521-32.Full text  Abstract

113. Gordon H, Burisch J, Ellul P, et al. ECCO guidelines on extraintestinal manifestations in inflammatory bowel disease. J Crohns Colitis. 2024 Jan 27;18(1):1-37.Full text

114. Bischoff SC, Bager P, Escher J, et al. ESPEN guideline on clinical nutrition in inflammatory bowel disease. Clin Nutr. 2023 Mar;42(3):352-79.Full text  Abstract

115. Mahawar KK, Reid A, Graham Y, et al. Oral vitamin B12 supplementation after Roux-en-Y gastric bypass: a systematic review. Obes Surg. 2018 Jul;28(7):1916-23. Abstract

116. Bischoff SC, Ockenga J, Eshraghian A, et al. Practical guideline on obesity care in patients with gastrointestinal and liver diseases - Joint ESPEN/UEG guideline. Clin Nutr. 2023 Jun;42(6):987-1024.Full text  Abstract

117. Homan J, Schijns W, Aarts EO, et al. An optimized multivitamin supplement lowers the number of vitamin and mineral deficiencies three years after Roux-en-Y gastric bypass: a cohort study. Surg Obes Relat Dis. 2016 Mar-Apr;12(3):659-67. Abstract

118. Finkelstein JL, Fothergill A, Venkatramanan S, et al. Vitamin B12 supplementation during pregnancy for maternal and child health outcomes. Cochrane Database Syst Rev. 2024 Jan 8;1(1):CD013823.Full text  Abstract

119. Procter SB, Campbell CG. Position of the Academy of Nutrition and Dietetics: nutrition and lifestyle for a healthy pregnancy outcome. J Acad Nutr Diet. 2014 Jul;114(7):1099-103.Full text  Abstract

120. Iacobucci G. Consider intramuscular injections for older people with vitamin B(12) deficiency, says NICE. BMJ. 2023 Jul 11;382:1604. Abstract

121. Andrès E, Dali-Youcef N, Vogel T, et al. Oral cobalamin (vitamin B(12)) treatment: an update. Int J Lab Hematol. 2009 Feb;31(1):1-8.Full text  Abstract

122. Rajan S, Wallace JI, Brodkin KI, et al. Response of elevated methylmalonic acid to three dose levels of oral cobalamin in older adults. J Am Geriatr Soc. 2002 Nov;50(11):1789-95. Abstract

123. Eussen SJ, de Groot LC, Clarke R, et al. Oral cyanocobalamin supplementation in older people with vitamin B12 deficiency: a dose-finding trial. Arch Intern Med. 2005 May 23;165(10):1167-72.Full text  Abstract

124. Andrès E, Fothergill H, Mecili M. Efficacy of oral cobalamin (vitamin B12) therapy. Expert Opin Pharmacother. 2010 Feb;11(2):249-56. Abstract

125. Beyer TL, Dryden RM. Basal cell carcinoma masquerading as ectropion. Case report. Arch Ophthalmol. 1988 Feb;106(2):170-1. Abstract

126. Stein J, Geisel J, Obeid R. Association between neuropathy and B-vitamins: a systematic review and meta-analysis. Eur J Neurol. 2021 Jun;28(6):2054-64.Full text  Abstract

127. Healton EB, Savage DG, Brust JC, et al. Neurologic aspects of cobalamin deficiency. Medicine (Baltimore). 1991 Jul;70(4):229-45. Abstract

128. Markun S, Gravestock I, Jäger L, et al. Effects of vitamin B12 supplementation on cognitive function, depressive symptoms, and fatigue: a systematic review, meta-analysis, and meta-regression. Nutrients. 2021 Mar 12;13(3):923.Full text  Abstract

129. Syed EU, Wasay M, Awan S. Vitamin B12 supplementation in treating major depressive disorder: a randomized controlled trial. Open Neurol J. 2013;7:44-8.Full text  Abstract

130. Vogel T, Dali-Youcef N, Kaltenbach G, et al. Homocysteine, vitamin B12, folate and cognitive functions: a systematic and critical review of the literature. Int J Clin Pract. 2009 Jul;63(7):1061-7. Abstract

131. McCleery J, Abraham RP, Denton DA, et al. Vitamin and mineral supplementation for preventing dementia or delaying cognitive decline in people with mild cognitive impairment. Cochrane Database Syst Rev. 2018 Nov 1;11(11):CD011905.Full text  Abstract

132. Laird EJ, O'Halloran AM, Molloy AM, et al. Low vitamin B(12) but not folate is associated with incident depressive symptoms in community-dwelling older adults: a 4-year longitudinal study. Br J Nutr. 2023 Jul 28;130(2):268-75. Abstract

133. Niklewicz A, Smith AD, Smith A, et al. The importance of vitamin B(12) for individuals choosing plant-based diets. Eur J Nutr. 2023 Apr;62(3):1551-9.Full text  Abstract

134. Seal EC, Metz J, Flicker L, et al. A randomized, double-blind, placebo-controlled study of oral vitamin B12 supplementation in older patients with subnormal or borderline serum vitamin B12 concentrations. J Am Geriatr Soc. 2002 Jan;50(1):146-51. Abstract