In routine OPD practice, patients frequently present with nonspecific complaints—persistent fatigue, tingling in the feet, imbalance, memory decline, irritability, or even treatment-resistant anemia. Increasingly, clinicians are revisiting Vitamin B12 deficiency as an under-recognized contributor, particularly in elderly patients, individuals on long-term metformin or proton pump inhibitors, strict vegetarians, and those with gastrointestinal disorders. Clinically, the absence of classical macrocytic anaemia does not exclude deficiency.
Neurological symptoms may precede hematologic changes, and MCV can remain normal in early stages. Borderline serum B12 levels (200–350 pg/mL) often create diagnostic uncertainty; in such cases, elevated methylmalonic acid or homocysteine can support functional deficiency where testing is accessible. Importantly, peripheral neuropathy due to B12…
