A Patient's Guide to Vitamin B12 Deficiency

Published by Dr. Kasturi Mandal | Last updated: September 2025

What Is Vitamin B12 Deficiency?

Vitamin B12 (also called cobalamin) is an essential nutrient for red blood cell production, nerve function, and DNA synthesis. A deficiency occurs when your body doesn’t have enough B12 to function properly, leading to anemia and potential nerve damage over time.

Common Symptoms of B12 Deficiency

Symptoms may develop slowly and can be varied, affecting your entire body.

General: Fatigue, weakness, pale or jaundiced skin, shortness of breath.
Neurological: Numbness or tingling in hands and feet, balance problems, memory issues, or mood changes.
Other: A swollen, red tongue (glossitis), mouth ulcers, or heart palpitations.

A person looking tired and fatigued, representing a common symptom of B12 deficiency. — Fatigue and neurological symptoms like tingling are key indicators of a possible B12 deficiency.

Causes of B12 Deficiency

The most common causes include:

pernicious anemia: An autoimmune condition that prevents the stomach from absorbing B12.
Dietary Deficiency: Common in strict vegans or vegetarians who do not supplement, as B12 is not naturally found in plant foods.
Malabsorption: Caused by conditions like celiac disease, Crohn’s, or previous gastric surgery.
Medications: Long-term use of metformin (for diabetes) or acid-reducing drugs (like PPIs).

Diagnosis and Treatment

Diagnosis is confirmed through blood tests that check your serum B12 level, a complete blood count (CBC), and sometimes levels of MMA and homocysteine. Treatment depends on the cause:

For **dietary deficiency**, high-dose oral B12 supplements are effective.
For **malabsorption or pernicious anemia**, B12 injections are required, often for life.

A flat lay of B12-rich foods including salmon, eggs, cheese, and fortified cereal. — B12 is found in animal products like fish, meat, eggs, and dairy, as well as in fortified foods.

Living Well with B12 Deficiency