Advances in Diabetes & Endocrinology
Review Article
Vitamin D3 and Vitamin B12 in Type 2 Diabetes Mellitus: Implications for Glycemic Control and Diabetic Complications-A Narrative Review
Sibi Das*
Department of Medicine, NC Medical College, Israna, Panipat, Haryana, India.
*Address for Correspondence:Dr. Sibi Das, Department of Medicine, NC Medical College,
Israna, Panipat, Haryana, India. E-mail Id: sdsilvanose@gmail.com
Submission: 25 May, 2026
Accepted: 18 June, 2026
Published: 20 June, 2026
Copyright: © 2026 Das S. This is an open access article
distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction
in any medium, provided the original work is properly cited.
Abstract
Type 2 diabetes mellitus (T2DM) is a major global metabolic disorder associated
with significant morbidity, mortality, and healthcare burden. Beyond hyperglycemia
and insulin resistance, growing evidence indicates that micronutrient deficiencies,
particularly vitamin D3 and vitamin B12 deficiencies, contribute substantially to
the pathogenesis, progression, and complications of T2DM. This narrative review
summarizes current evidence regarding the epidemiology, pathophysiological
mechanisms, clinical implications, and therapeutic significance of vitamin D3 and
vitamin B12 in patients with T2DM. Vitamin D3 plays an essential role in glucose
homeostasis through modulation of pancreatic β-cell function, insulin secretion, insulin
sensitivity, and inflammatory responses. Deficiency of vitamin D3 has been associated
with poor glycemic control, increased insulin resistance, endothelial dysfunction, and
higher risk of diabetic microvascular and macrovascular complications.
Vitamin B12 deficiency is also highly prevalent among patients with T2DM, especially in individuals receiving long-term metformin therapy. Chronic vitamin B12 deficiency may result in peripheral neuropathy, megaloblastic anaemia, cognitive impairment, and elevated cardiovascular risk due to hyperhomocysteinemia. Importantly, vitamin B12 deficiency-related neuropathy may overlap with diabetic neuropathy, potentially leading to underdiagnosis and delayed treatment.
Recent clinical studies suggest that combined deficiencies of vitamin D3 and vitamin B12 may adversely influence metabolic control and accelerate diabetic complications. Early identification and correction of these deficiencies may improve insulin sensitivity, glycemic status, neuropathic symptoms, and overall quality of life in diabetic patients.
This review discusses the epidemiological associations, underlying pathophysiological mechanisms, clinical implications, and therapeutic significance of vitamin D3 and vitamin B12 in type 2 diabetes mellitus. The review also highlights the importance of routine micronutrient assessment as part of comprehensive diabetes management strategies.
Vitamin B12 deficiency is also highly prevalent among patients with T2DM, especially in individuals receiving long-term metformin therapy. Chronic vitamin B12 deficiency may result in peripheral neuropathy, megaloblastic anaemia, cognitive impairment, and elevated cardiovascular risk due to hyperhomocysteinemia. Importantly, vitamin B12 deficiency-related neuropathy may overlap with diabetic neuropathy, potentially leading to underdiagnosis and delayed treatment.
Recent clinical studies suggest that combined deficiencies of vitamin D3 and vitamin B12 may adversely influence metabolic control and accelerate diabetic complications. Early identification and correction of these deficiencies may improve insulin sensitivity, glycemic status, neuropathic symptoms, and overall quality of life in diabetic patients.
This review discusses the epidemiological associations, underlying pathophysiological mechanisms, clinical implications, and therapeutic significance of vitamin D3 and vitamin B12 in type 2 diabetes mellitus. The review also highlights the importance of routine micronutrient assessment as part of comprehensive diabetes management strategies.