Vitamin B12 deficiency is more common — and more dangerous — than many realize. Because it develops gradually, symptoms are often dismissed as “normal aging.” Numbness or tingling in the hands and feet, trouble walking, fatigue, memory problems and even mood changes can all stem from inadequate B12 levels. In more severe cases, deficiency can lead to anemia, nerve damage and significant cognitive decline.
B12 is essential for red blood cell production, nerve health and DNA synthesis. Unlike many nutrients, it is found almost exclusively in animal foods such as meat, eggs and dairy. Strict vegetarians and vegans, older adults with reduced stomach acid and people taking acid-blocking medications are at higher risk. Weight-loss surgery and digestive disorders can also impair absorption, meaning some people may not absorb enough B12 even if their diet appears adequate.
Early detection matters. A simple blood test can confirm low levels, and treatment may involve high-dose oral supplements or injections in more advanced cases. While B12 is often promoted online as a cure-all for everything from fatigue to Alzheimer’s disease, evidence supports its use primarily for correcting deficiency — not for boosting energy beyond normal levels. The key is prevention, particularly for those in higher-risk groups.
SOURCE:
Harvard Health Publishing, February 20, 2026