Correlation of Vitamin B12 Deficiency with Diabetic Neuropathy in Type II Diabetics on Long-term Metformin Therapy

Abstract

Background: Vitamin B12 deficiency is a well-documented side effect of long-term metformin use in patients with diabetes. However, its potential relationship with diabetic neuropathy remains underexplored in the local diabetic population.

Objective: This study aimed to determine the correlation between vitamin B12 deficiency and diabetic neuropathy in type II diabetics on long-term metformin therapy.

Study type, settings & duration: This cross-sectional analytical study was conducted at Rahbar Medical College/ Punjab Rangers Teaching Hospital Lahore from May to November 2024.

Methodology: Total 150 type II diabetics taking metformin >12 months were included. Vitamin B12 levels estimated using chemiluminescence immunoassay and were considered deficient. Diabetic neuropathy was diagnosed by using Michigan Neuropathy Screening Instrument.

Results: Out of total 150 type II diabetics, 80 (53.3%) were women and 70 (46.7%) were men. Overall mean age was 63±11 years. Among total 42 (28%) patients with vitamin B12 level below normal (≤ 300 pg/mL), 10 (6.7%) were deficient and 32 (21.3%) were inadequate. Diabetic neuropathy was diagnosed in 32 (21.3%) patients. Of them, total 22 (68.7%) patients had vitamin B12 level below normal (≤ 300 pg/mL), that included 10 (31.3%) deficient and 12 (37.5%) inadequate. Duration of metformin use and B12 levels were not associated [coefficient: 0.70, 95% CI: -0.40, 1.71]. However, diabetic neuropathy showed a strong negative association with B12 levels [coefficient: -115.6, 95% CI: -164.1, -67.0].

Conclusion: There is a strong link between low vitamin B12 levels and diabetic neuropathy in long-term metformin users, suggesting B12 deficiency as a modifiable risk factor. ......