Concentration problems, tingling in hands, burning tongue, fatigue that doesn't go away? In vegetarians/vegans (but not only), a vitamin B12 deficiency can hide behind discrete symptoms at first, then clearer. This guide helps you recognize signs, choose the right assessment, and implement simple and regular supplementation, adapted to your situation.
Neuro/hemato symptoms
- Neurological: paresthesias (tingling/numbness), balance problems, memory/concentration.
- Hematological: macrocytic anemia, fatigue, pallor.
- Oral: smooth/burning tongue (glossitis).
- Psychological: depression, irritability.
Neurological damage can become irreversible if deficiency prolonged. Early diagnosis is crucial.
Assessment
- Serum B12: first test, but low sensitivity (false negatives possible).
- Holotranscobalamin (holoTC): more specific, detects early deficiency.
- Homocysteine/methylmalonic acid (MMA): elevated in functional deficiency.
B12 < 200 pg/mL: probable deficiency. 200–400 pg/mL: borderline, consider holoTC/MMA. > 400 pg/mL: generally sufficient.
Causes
- Insufficient intake: vegetarian/vegan diet (B12 only in animal products).
- Malabsorption: pernicious anemia (intrinsic factor deficiency), Crohn's disease, bariatric surgery.
- Medications: metformin, PPIs (proton pump inhibitors).
- Age: reduced absorption in elderly.
Food sources
- Animal: meat, fish, eggs, dairy products.
- Fortified: plant beverages, breakfast products, nutritional yeast.
Systematic supplementation recommended (diet alone insufficient).
Doses
Prevention (vegetarians/vegans)
- Daily: 25–100 µg cyanocobalamin.
- Weekly: 1000 µg 2×/week or 2000 µg 1×/week.
Deficiency treatment
- Oral: 1000–2000 µg/day for 4–8 weeks, then maintenance.
- Intramuscular: 1000 µg/day or 1×/week (severe deficiency/malabsorption).
Cyanocobalamin vs methylcobalamin
- Cyanocobalamin: stable, cheap, recommended.
- Methylcobalamin: active form, but less stable; no proven advantage.
Interactions and precautions
- Metformin: reduces B12 absorption; monitor status.
- PPIs/H2 blockers: reduce absorption; consider supplementation.
- Folate: masks anemia from B12 deficiency without correcting neurological damage.
B12 is non-toxic even at high doses (water-soluble). No known upper limit.
FAQ
How long to supplement?
Lifelong for vegetarians/vegans and malabsorption cases.
Can B12 be taken daily?
Yes, safely. Alternatively weekly high doses.
B12 morning or evening?
Doesn't matter; with or without food (better absorption on empty stomach but not critical).
