Published: 2022-01-25

Effect of metformin on serum vitamin B12 and red blood cell indices in North Indian subjects with diabetes mellitus

Amir Husain, Haroon Subhan Khan, Sheelu Shafiq Siddiqi, Amit Mukherjee


Background: Diabetes mellitus (DM) affecting almost half a billion people worldwide and India is amongst the top ten countries of adults with diabetes. Metformin, the first-line therapy for diabetes, is associated with vitamin B12 malabsorption and subsequently, the development of vitamin B12 deficiency/insufficiency could manifest severe complications like neuropathy or anemia in the future. This study evaluated the effect of metformin on vitamin B12 and RBC indices in the North Indian population.

Methods:This study was executed at a tertiary care hospital. 35 T2DM (type 2 DM) participants with ongoing metformin therapy were compared with 27 T2DM participants without metformin therapy. Participants were recruited from outpatient after diagnosis as per American diabetes association (ADA) criteria.

Results: Metformin-treated participants had significantly low hemoglobin (t=2.096, df=60, 0.0403) compared to untreated participants. Similarly, MCHC was significantly lower in the metformin group (mean=33.28 gm/dl) compared to non-metformin group (mean=34.53 gm/dl) (t=2.745, df=60, p=0.0080). Moreover, there was a strong negative correlation (r=-0.4613, p=0.0053) among vitamin B12 and MCV in metformin group. There was no statistically significant correlation between vitamin B12 and RBC indices (MCV, MCH, MCHC) in the non-metformin group. Analyzing contingency table (Fisher’s exact test), we found no major difference (p=0.2002) between two groups of vitamin B12 with an odds ratio of 2.026 (95% CI=0.7366 to 5.633). Unpaired t test also confirmed insignificancy (t=0.04077, df=60, p=0.9676).

Conclusions:Strong negative correlation was observed between vitamin B12 and MCV. Despite the insignificant difference of vitamin B12 between metformin and non-metformin groups, significantly low MCHC was found in metformin-treated participants.



MMetformin, RBC indices, Type 2 diabetes mellitus, Vitamin B12 deficiency

Full Text:



International Diabetes Federation. Diabetes Atlas. 9th ed. IDF; 2019.

Bell DSH. Metformin-induced vitamin B12 deficiency presenting as a peripheral neuropathy. South Med J. 2010;103(3):265-7.

Nathan DM, Buse JB, Davidson MB, Ferrannini E, Holman RR, Sherwin R, et al. Medical management of hyperglycemia in type 2 diabetes: a consensus algorithm for the initiation and adjustment of therapy. Diabetes Care. 2009;32(1):193-203.

Salpeter SR, Buckley NS, Kahn JA, Salpeter EE. Meta-analysis: metformin treatment in persons at risk for diabetes mellitus. Am J Med. 2008;121(2):149-57.

Glueck CJ, Fontaine RN, Wang P, Subbiah MT, Weber K, Illig E, et al. Metformin reduces weight, centripetal obesity, insulin, leptin, and low-density lipoprotein cholesterol in nondiabetic, morbidly obese subjects with body mass index greater than 30. Metabolism. 2001;50(7):856-61.

Cicero AFG, Tartagni E, Ertek S. Metformin and its clinical use: new insights for an old drug in clinical practice. Arch Med Sci. 2012;8(5):907.

Giovannucci E, Harlan DM, Archer MC, Bergenstal RM, Gapstur SM, Habel LA, et al. Diabetes and cancer: a consensus report. Diabetes Care. 2010;33(7):1674-85.

Berchtold P, Bolli P, Arbenz U, Keiser G. Disturbance of intestinal absorption following metformin therapy (observations on the mode of action of biguanides. Diabetologia. 1969;5(6):405-12.

Tomkin GH, Hadden DR, Weaver JA, Montgomery DAD. Vitamin-B12 status of patients on long-term metformin therapy. Br Med J. 1971;2(5763):685.

Reinstatler L, Qi YP, Williamson RS, Garn JV, Oakley GP. Association of biochemical B12 deficiency with metformin therapy and vitamin b12 supplements: the National health and nutrition examination survey, 1999-2006. Diabetes Care. 2012;35(2):327.

Jansen EHJM, Beekhof PK, Cremers JWJM, Schenk E. Long-term (in)stability of folate and vitamin B12 in human serum. Clin Chem Lab Med. 2012;50(10):1761-3.

Doyle-Delgado K, Chamberlain JJ, Shubrook JH, Skolnik N, Trujillo J. Pharmacologic approaches to glycemic treatment of type 2 diabetes: synopsis of the 2020 American diabetes association’s standards of medical care in diabetes clinical guideline. Ann Intern Med. 2020;173(10):813-21.

El-Mir MY, Nogueira V, Fontaine E, Avéret N, Rigoulet M, Leverve X. Dimethylbiguanide inhibits cell respiration via an indirect effect targeted on the respiratory chain complex I. J Biol Chem. 2000;275(1):223-8.

Zhou G, Myers R, Li Y, Chen Y, Shen X, Fenyk-Melody J, et al. Role of AMP-activated protein kinase in mechanism of metformin action. J Clin Invest. 2001;108(8):1167-74.

Miller RA, Chu Q, Xie J, Foretz M, Viollet B, Birnbaum MJ. Biguanides suppress hepatic glucagon signalling by decreasing production of cyclic AMP. Nature. 2013;494(7436):256-60.

Aroda VR, Edelstein SL, Goldberg RB, Knowler WC, Marcovina SM, Orchard TJ, et al. Long-term metformin use and vitamin B12 deficiency in the diabetes prevention program outcomes study. J Clin Endocrinol Metab. 2016;101(4):1754.

Ganguly P, Alam SF. Role of homocysteine in the development of cardiovascular disease. Nutr J. 2015;14:6.

Sato Y, Ouchi K, Funase Y, Yamauchi K, Aizawa T. Relationship between metformin use, vitamin B12 deficiency, hyperhomocysteinemia and vascular complications in patients with type 2 diabetes. Endocr J. 2013;60(12):1275-80.

Sugawara K, Okada Y, Hirota Y, Sakaguchi K, Ogawa W. Relationship between metformin use and vitamin B 12 status in patients with type 2 diabetes in Japan. J Diabetes Investig. 2020;11:917-22.

Lohmann AE, Liebman MF, Brien W, Parulekar WR, Gelmon KA, Shepherd LE, et al. Effects of metformin versus placebo on Vitamin B12 metabolism in non-diabetic breast cancer patients in CCTG MA.32 HHS Public Access. Breast Cancer Res Treat. 2017;164(2):371-8.

Jager JD, Kooy A, Lehert P, Wulffelé MG, Kolk JVD, Bets D, 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;340(7757):1177.

Gonzalez-Gross M, Sola R, Albers U, Barrios L, Alder M, Castillo MJ, et al. B-vitamins and homocysteine in Spanish institutionalized elderly. Int J Vitam Nutr Res. 2007;77(1):22-33.

Raizada N, Jyotsna VP, Sreenivas V, Tandon N. Serum vitamin B12 levels in type 2 diabetes patients on metformin compared to those never on metformin: a cross-sectional study. Indian J Endocrinol Metab. 2017;21(3):424-8.