Vitamin B12 Deficiency: Causes, Symptoms & Testing Guide

By Dashvanth Healthcare Medical Team · Reviewed by our specialists · East Delhi

Why B12 Deficiency Is a Major Issue in India

Vitamin B12 is found almost exclusively in animal products — meat, fish, eggs, dairy. India's high prevalence of vegetarianism (30–40% of population) makes B12 deficiency endemic. Additionally, Helicobacter pylori infection (extremely common in India) impairs B12 absorption.

What B12 Does

• DNA synthesis and red blood cell production
• Myelin formation — essential for nerve function
• Brain and cognitive function
• Homocysteine metabolism (elevated homocysteine = cardiovascular and stroke risk)

Symptoms of Deficiency

• Fatigue and weakness (megaloblastic anaemia)
• Numbness and tingling in hands and feet (peripheral neuropathy)
• Difficulty walking, balance problems (subacute combined degeneration of cord in severe cases)
• Memory problems, brain fog, mood disturbance
• Glossitis (smooth, painful tongue)
• Yellowing of skin (jaundice-like)

Testing

• Serum Vitamin B12: Normal 200–900 pg/mL; Deficient <200 pg/mL; Borderline 200–300 pg/mL
• Serum homocysteine: elevated in B12 (and folate) deficiency — functional marker of deficiency even with "normal" B12 levels
• MMA (methylmalonic acid): most sensitive functional B12 marker — elevated even with borderline B12

Treatment

• Oral B12 (cyanocobalamin 500–1000 mcg/day): effective even without intrinsic factor as passive absorption occurs at high doses
• Intramuscular injections: for severe deficiency or malabsorption (monthly after loading doses)
• Vegetarians/vegans: lifelong supplementation needed