Vitamin B12 Deficiency

Overview

Vitamin B12 is needed to make red blood cells and to keep the nervous system healthy. Deficiency can cause a macrocytic anaemia (large red cells and low haemoglobin) and, importantly, nerve and brain symptoms that can occur even before the anaemia. It is common in strict vegetarians and vegans, in older people, and in conditions that impair absorption. This page focuses on B12 deficiency; the red-cell pattern it produces is covered on the Macrocytic Anaemia page.

Common causes

• Diet low in B12 — strict vegetarian or vegan diets, as B12 is found mainly in animal foods.
• Pernicious anaemia — an autoimmune condition that blocks absorption by stopping intrinsic factor production.
• Stomach or small-bowel surgery, including weight-loss surgery.
• Coeliac disease, Crohn’s disease or other malabsorption.
• Certain medicines — long-term metformin or acid-suppressing drugs.
• Older age, with reduced absorption.

Symptoms

Blood-related symptoms include tiredness, breathlessness and paleness from the anaemia. Nervous-system symptoms — which can appear without anaemia — include tingling or numbness in the hands and feet, unsteadiness or balance problems, memory and concentration difficulty, mood change, and a sore, smooth tongue. Because nerve symptoms can become permanent if untreated, B12 deficiency should be corrected promptly. See Macrocytic Anaemia and Fatigue Due to Anaemia.

Evaluation and investigations

Diagnosis is made from a serum B12 level, alongside a complete blood count showing large red cells (high MCV) and a peripheral smear. When the level is borderline, additional tests such as homocysteine and methylmalonic acid help confirm deficiency. The cause is sought with a dietary history, assessment for pernicious anaemia (antibody tests), and review of medicines and gut health. Folate is checked at the same time, as the two deficiencies can coexist and look similar. See Folate Deficiency and Abnormal Test Results.

Management overview

Treatment depends on the cause. When absorption is the problem — as in pernicious anaemia, gut surgery or malabsorption — B12 is given by injection, usually frequently at first then as a maintenance dose. When the cause is dietary, high-dose oral B12 can be effective under guidance. Folate is corrected alongside B12 if needed, but folate should not be given alone when B12 deficiency is present, as it can worsen nerve symptoms. The response is confirmed with repeat blood counts and monitoring of symptoms. See Macrocytic Anaemia and Nutritional Anaemia.

Warning signs — seek prompt care

• Tingling, numbness, unsteadiness or memory change with a low or borderline B12 — prompt treatment to avoid permanent nerve damage.
• Severe anaemia with breathlessness or fainting.

How we help

Dr. Nayak confirms B12 deficiency, identifies whether the cause is dietary or absorptive, and builds a replacement plan — injections or oral — with monitoring of blood counts and nerve symptoms. Consultations are available in-clinic in Bhubaneswar and over teleconsultation.

Related conditions and patient concerns

• Anaemia
• Macrocytic Anaemia
• Folate Deficiency
• Nutritional Anaemia
• Digestive Problems
• Fatigue, Weakness & General Symptoms