💊 Nutrition
Vitamin B12 Deficiency — Symptoms, Causes & Treatment (2026)
B12 deficiency is extremely common in vegans and older adults, causing fatigue and nerve damage. Learn symptoms, sources, and supplement guidance. Updated January 2026.
Key Takeaways
- B12 deficiency affects 1 in 6 adults over 60 and all unsupplemented long-term vegans
- Neurological damage can be irreversible if untreated for years — act early
- Fatigue, tingling hands/feet, brain fog are the most common early symptoms
- All vegans need to supplement with at least 2,000mcg cyanocobalamin weekly
- Cyanocobalamin is the most stable, cheapest, and best-studied supplement form
In This Article
Why B12 Is Essential
Vitamin B12 enables DNA synthesis, red blood cell formation, and maintains myelin sheaths protecting nerve fibres. Deficiency causes megaloblastic anaemia and, over time, irreversible nerve damage.
1 in 6
Adults over 60 have low B12
~100%
Unsupplemented long-term vegans develop deficiency
2.4mcg
Daily requirement (RDA)
High-Risk Groups
- Vegans and vegetarians — B12 only in animal products
- Adults over 50 — stomach acid declines, impairing absorption
- Metformin users — impairs B12 absorption in up to 30%
- People on PPIs — acid suppression reduces B12 release
- Pernicious anaemia — requires B12 injections
Symptoms
Neurological (Often First)
- Tingling or numbness in hands and feet
- Balance problems and difficulty walking
- Memory decline and cognitive changes
- Depression and mood disturbances
Haematological
- Profound fatigue not relieved by rest
- Breathlessness on minimal exertion
- Pale or slightly yellowed skin
| Food | B12 per serving | % RDA |
|---|---|---|
| Beef liver (85g) | 70mcg | 2,917% |
| Salmon (100g) | 3.2mcg | 133% |
| Eggs (2 large) | 1.5mcg | 63% |
| Milk (240ml) | 1.2mcg | 50% |
| Nutritional yeast (15g, fortified) | 2.4mcg | 100% |
⚠️ Get Tested Before High-Dose Supplementing
Ask your GP for serum B12 before supplementing. High-dose B12 can mask haematological signs while nerve damage continues. Pernicious anaemia requires B12 injections — oral supplements are insufficient.🔢 Free Tool
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Open Free Calculator →Frequently Asked Questions
Do vegans always need B12 supplements?▼
Yes — without exception. B12 exists only in animal products. There are no reliable plant sources. All vegans should take 2,000mcg cyanocobalamin weekly or 250mcg daily.
Which B12 supplement is best?▼
Cyanocobalamin is recommended by the NHS — most stable, cheapest, and best-studied. Methylcobalamin is well-absorbed but less stable. Both work for most people.
Can B12 deficiency be reversed?▼
Early-stage deficiency is fully reversible with supplementation. However, severe long-term nerve damage may be permanent — why early detection matters.
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⚕️ Medical Disclaimer: For informational purposes only. Not a substitute for professional medical advice. Always consult a qualified healthcare professional.
EC
Dr. Emma Clarke, PhD, RD
WellCalc Medical Contributor
All WellCalc articles are reviewed by qualified healthcare professionals following NHS, AHA, and WHO guidelines.