BACKGROUND: Vitamin B12 (B12), playing the role of a coenzyme in one-carbon metabolism, is an important vitamin necessary for human health. OBJECTIVES: To systematically review evidence to identify the complications of B12 deficiency among women. METHODS: We conducted a systematic search of quantitative studies on disorders associated with B12 deficiency among women, published in English in the last 25 years (1999-2024), using electronic databases such as Scopus, Web of science, CINAHL, PubMed, and Medline. CONCLUSION: The search produced 28 full-text articles. B12 deficiency prevalence among women identified by the selected studies ranges from 0.6% to 45.5%. The deficiency of B12 is connected with the risk for depression/post-partum depression, breast cancer, recurrent pregnancy loss, gestational diabetes mellitus, insulin resistance, and obesity among women. It is necessary to monitor and correct the B12 deficiency among women in order to prevent complications.