29/10/2026
Vitamin B12 Deficiency: Causes, Signs & Management
Vitamin B12 deficiency occurs when the body does not get enough vitamin B12 or cannot absorb it properly. Vitamin B12 is essential for red blood cell formation, nerve function, and DNA synthesis. Deficiency can cause fatigue, anaemia, numbness, tingling, memory problems, and neurological damage if left untreated.
🔹 Common causes / risk factors
➟ Pernicious anaemia — autoimmune impairment of vitamin B12 absorption
➟ Low dietary intake, especially with strict vegan diets without supplementation
➟ Atrophic gastritis — reduced stomach acid and intrinsic factor production
➟ Crohn's disease affecting the terminal ileum
➟ Previous stomach or intestinal surgery
➟ Long-term metformin use
➟ Prolonged use of proton pump inhibitors, such as omeprazole
➟ Increasing age and impaired vitamin B12 absorption
➟ Nitrous oxide exposure, which can inactivate vitamin B12
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🔹 Common signs
➟ Persistent fatigue and weakness
➟ Pale skin due to anaemia
➟ Numbness or tingling in the hands and feet
➟ Dizziness or lightheadedness
➟ Shortness of breath during physical activity
➟ Sore, red, or smooth tongue (glossitis)
➟ Loss of appetite
➟ Difficulty concentrating
➟ Heart palpitations
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🔹 Neurological signs
➟ Peripheral neuropathy — tingling, numbness, or burning sensations
➟ Difficulty walking or maintaining balance
➟ Reduced vibration and position sense
➟ Muscle weakness
➟ Impaired coordination
➟ Memory problems or cognitive changes
➟ Depression or irritability
➟ Severe deficiency may cause subacute combined degeneration of the spinal cord
Neurological symptoms can occur even without anaemia.
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🔹 Other possible signs
➟ Mouth ulcers
➟ Glossitis — smooth, painful, red tongue
➟ Reduced appetite and weight loss
➟ Gastrointestinal discomfort
➟ Visual disturbances in rare cases
➟ Mood or behavioural changes
➟ Increased skin pigmentation in some patients
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🔹 Typical symptom patterns
➟ Symptoms often develop gradually over months or years
➟ Fatigue may appear before obvious neurological problems
➟ Tingling may begin in the feet and later affect the hands
➟ Balance difficulties may worsen with progression
➟ Memory or concentration problems may occur
➟ Prolonged untreated deficiency can cause irreversible nerve damage
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🔹 Diagnosis
➟ Complete blood count (CBC) to assess anaemia
➟ Serum vitamin B12 level
➟ Mean corpuscular volume (MCV) — may be elevated
➟ Peripheral blood smear may show macro-ovalocytes and hypersegmented neutrophils
➟ Methylmalonic acid (MMA) — often elevated in B12 deficiency
➟ Homocysteine — may also be elevated
➟ Anti-intrinsic factor antibodies when pernicious anaemia is suspected
➟ Folate and iron studies when indicated
A normal MCV does not exclude vitamin B12 deficiency.
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🔹 Core management
➟ Identify and treat the underlying cause
➟ Oral vitamin B12 supplements for many patients
➟ Intramuscular vitamin B12 injections when indicated, particularly with severe neurological symptoms or certain absorption disorders
➟ Lifelong replacement may be necessary in pernicious anaemia or irreversible malabsorption
➟ Review medicines contributing to deficiency
➟ Correct other nutritional deficiencies when present
➟ Monitor blood counts, symptoms, and neurological recovery
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🔹 Vitamin B12-rich foods
➟ Fish and seafood
➟ Meat and poultry
➟ Eggs
➟ Milk and yogurt
➟ Cheese
➟ Fortified breakfast cereals
➟ Fortified plant-based milk
➟ Fortified nutritional yeast
Vitamin B12 is naturally found mainly in animal-derived foods. People following vegan diets generally need reliable fortified foods or supplements.
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🔹 Lifestyle / self-care
➟ Maintain a balanced diet containing adequate vitamin B12
➟ Take prescribed supplements consistently
➟ Follow a supplementation plan if vegan
➟ Attend recommended blood tests
➟ Report persistent numbness or balance difficulties
➟ Discuss long-term metformin use with a healthcare professional
➟ Avoid recreational nitrous oxide use
➟ Follow up if symptoms do not improve with treatment
➟Optimise stomach acid and enzyme function
➟If taking PPI medication longer than 6 weeks, request a review and book ro see a nutritional therapist for guidance on digestive health
➟Consider B12 injections if suffering digestive problems as many can't absorb B12 supplements when digestion is sub optimal
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🔹 What not to do
➟ Don't ignore persistent tingling or numbness
➟ Don't assume all fatigue is caused by vitamin deficiency
➟ Don't treat suspected B12 deficiency with folic acid alone
➟ Don't stop B12 replacement prematurely when lifelong treatment is required
➟ Don't rely on unfortified plant foods as a reliable B12 source
➟ Don't assume a normal blood count rules out deficiency
➟ Don't delay treatment when neurological symptoms are present
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🔹 Possible complications
➟ Megaloblastic anaemia
➟ Peripheral neuropathy
➟ Subacute combined degeneration of the spinal cord
➟ Impaired balance and walking
➟ Cognitive impairment
➟ Depression and mood disturbances
➟ Optic neuropathy in rare cases
➟ Permanent neurological damage if treatment is delayed
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🔹 When to see a doctor
➟ Persistent fatigue or unexplained weakness
➟ Numbness or tingling in the hands and feet
➟ Difficulty walking or maintaining balance
➟ Persistent sore or smooth tongue
➟ Memory or concentration problems
➟ Anaemia detected on blood testing
➟ Risk factors such as vegan diet, pernicious anaemia, or intestinal disease
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🔹 Emergency warning
➟ Rapidly worsening weakness or difficulty walking
➟ Severe breathlessness or chest pain
➟ Fainting or marked weakness with severe anaemia
➟ Sudden confusion or significant neurological changes
➟ Sudden one-sided weakness or speech difficulty
These symptoms may indicate severe anaemia, progressive neurological injury, stroke, or another serious condition and require urgent or emergency medical assessment.
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🔹 High-Yield Points
➟ Vitamin B12 is also called cobalamin
➟ Essential for DNA synthesis, red blood cell production, and myelin maintenance
➟ Common causes include pernicious anaemia, malabsorption, dietary deficiency, and certain medicines
➟ Classic symptoms: Fatigue + pallor + glossitis + numbness and tingling
➟ Macrocytic megaloblastic anaemia is a characteristic finding
➟ Hypersegmented neutrophils may be seen on peripheral blood smear
➟ Methylmalonic acid and homocysteine are commonly elevated
➟ Neurological damage may occur without anaemia
➟ Oral or injectable vitamin B12 can correct deficiency
➟ Pernicious anaemia often requires lifelong vitamin B12 replacement
➟ Early treatment improves recovery and helps prevent permanent neurological complications
Medical disclaimer: This note is for education only and is not a substitute for professional medical advice, diagnosis, or treatment.
