SAT-643 Type 2 Diabetes Mellitus and Metformin: Double Trouble Causing Peripheral Neuropathy?

Abstract Disclosure: S.B. Karatela: None. J.M. Pathak: None. N.B. Trivedi: None. K.P. Shah: None. D.J. Shah: None. A.G. Patel: None. A. Parikh: None. A.J. Rajani: None. A. Patel: None. Type 2 diabetes mellitus (T2DM) is a growing global health concern, with complications like peripheral neuropathy (PN), retinopathy, and nephropathy affecting patients' quality of life. Metformin, the first-line oral treatment, is linked to vitamin B12 deficiency, which can cause hematologic abnormalities and worsen diabetic PN. While well-documented, this association remains underexplored in India, particularly regarding neuropathy severity and metformin dosage/duration. Given the high cost of serum vitamin B12 testing, we also aimed to evaluate hematologic (mean corpuscular volume, MCV) and clinical (Toronto clinical neuropathy score, TCNS) parameters as cost-effective screening tools. 92 T2DM patients (46 metformin users and 46 non-users) were assessed. Primary outcomes included vitamin B12 deficiency and PN, while secondary outcomes evaluated MCV and clinical PN as screening tools. Neuropathy was staged using TCNS. Statistical analysis was conducted using MedCalc version 20.210, with two-tailed p<0.05 considered significant. Results showed no significant difference in mean vitamin B12 levels between metformin users (410.78±558.86) and non-users (479.84±618.85), p=0.61. However, metformin users were 1.6 times more likely to develop PN (RR=1.6, 95% CI=1.09-2.34, p=0.015), with significantly higher rates of severe neuropathy (X2(3, N=92)=8.334, p=0.039). No significant correlation was found between metformin duration and vitamin B12 levels or neuropathy severity, but metformin dose significantly correlated with TCNS scores, explaining 9.9% of the variation (R2=0.099, F(1,44)=4.86, p=0.03). MCV as a screening tool for vitamin B12 deficiency showed sensitivity (2.2%, 95% CI: 0.1-11.5), specificity (100%, 95% CI: 92.3-100), and an overall accuracy of 51.1%. TCNS demonstrated sensitivity (56.5%, 95% CI: 41.1-71.1), specificity (43.5%, 95% CI: 28.9-58.9), and an overall accuracy of 50%. While metformin did not significantly lower vitamin B12 levels, this may be due to the study’s limited power. However, metformin use was significantly associated with PN development and severity in a dose-dependent manner. The low sensitivity of MCV and TCNS limits their utility as screening tools for B12 deficiency. A larger trial or meta-analysis is needed to confirm these findings and assess causality. Clinicians should monitor vitamin B12 levels to prevent PN progression in diabetic patients on long-term metformin therapy. Presentation: Saturday, July 12, 2025