Vitamin B12 deficiency
Symptoms, at-risk groups, and clinical context for vitamin b12 deficiency. Sourced from NIH Office of Dietary Supplements and StatPearls.
Vitamin B12 deficiency affects roughly 6% of US adults under 60 and ~20% over 60. It's especially common in vegans, the elderly, and long-term users of metformin or proton pump inhibitors. Untreated deficiency can cause IRREVERSIBLE neurological damage, so early detection matters.
Common symptoms
- Fatigue, weakness, and shortness of breath (from megaloblastic anemia)
- Numbness or tingling in the hands and feet (peripheral neuropathy)
- Cognitive issues — brain fog, memory problems, difficulty concentrating
- Mood changes — depression, irritability
- Sore or swollen tongue (glossitis), mouth ulcers
- Pale or jaundiced skin
- Balance problems or unsteady gait (in advanced cases)
At-risk groups
- Vegans and strict vegetarians (B12 is found almost exclusively in animal foods)
- Adults aged 60+ (atrophic gastritis reduces B12 absorption)
- Long-term metformin users (>4 years) — metformin reduces B12 absorption by up to 30%
- Long-term proton pump inhibitor users (omeprazole, pantoprazole, esomeprazole >1 year)
- People with pernicious anemia (autoimmune destruction of intrinsic factor)
- Post gastric bypass or ileal resection surgery patients
- People with Crohn's disease or celiac disease
When to see a doctor: If you fall into an at-risk group AND experience persistent fatigue plus neurological symptoms (numbness, tingling, balance issues, or memory problems), ask your doctor for a serum B12 test. Methylmalonic acid (MMA) and homocysteine are more sensitive markers when B12 is borderline.
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Related deficiencies
Nutrients with overlapping symptoms — useful when investigating an unclear clinical picture.