Prevalence of Vitamin B12 Deficiency in Type 2 Diabetic Patients on Long-Term Metformin Therapy

Vitamin B12 deficiency is a recognized complication in patients with type 2 diabetes mellitus (T2DM) undergoing long-term metformin therapy. Despite metformin's widespread use due to its efficacy and safety profile, it has been associated with reduced absorption of vitamin B12, which can lead to hematologic and neurologic complications. This study aimed to determine the prevalence of vitamin B12 deficiency and its associated risk factors among T2DM patients on prolonged metformin therapy in Peshawar, Pakistan.

A descriptive cross-sectional study was conducted in the outpatient departments of tertiary care hospitals in Peshawar from October 2024 to April 2025. A total of 320 T2DM patients aged 18 years and above who had been on metformin therapy were included. Data were collected through structured questionnaires and medical records, and serum vitamin B12 levels were measured using blood samples. Deficiency was defined as <200 pg/mL, borderline as 200-300 pg/mL, and normal as >300 pg/mL. Data were analyzed using SPSS version 20 (IBM Corp., Armonk, NY, US), applying chi-square tests to assess associations.

Out of 329 participants, 65.7% (n=216) had vitamin B12 deficiency, 24.3% (n=80) had borderline levels, and only 10% (n=33) had normal vitamin B12 levels. A statistically significant association was found between vitamin B12 deficiency and increasing age (p=0.003), higher BMI (p=0.012), longer duration of diabetes (p=0.025), and prolonged metformin use (p<0.001).

The study reveals a high prevalence of vitamin B12 deficiency among T2DM patients on long-term metformin therapy. The deficiency is significantly associated with older age, obesity, longer diabetes duration, and extended metformin use. Routine screening and early supplementation of vitamin B12 should be considered in diabetic patients on prolonged metformin treatment to prevent potential complications.