Overview
- Coverage in early August 2026 consolidates guidance that at‑risk groups—vegans, older adults, people with gastrointestinal disease, post‑bariatric surgery patients, and long‑term users of proton‑pump inhibitors or metformin—should have targeted B12 testing rather than routine high‑dose supplementation.
- Clinicians and reports recommend using holotranscobalamin (Holo‑TC) and methylmalonic acid (MMA) to diagnose deficiency because total serum B12 alone can miss cases and values under 200 pg/ml are commonly treated as deficient.
- Public‑health intake benchmarks remain modest: the Deutsche Gesellschaft für Ernährung (DGE) recommends about 4 µg/day for adults and the Bundesinstitut für Risikobewertung (BfR) advises a 25 µg/day cap for over‑the‑counter supplements in otherwise healthy people.
- Oral absorption is biologically limited so higher doses are only partly taken up—about 50% of 1 µg, 20% of 5 µg and roughly 5% of 25 µg—so therapeutic regimens for confirmed deficiency often use much larger oral doses (500–1000 µg/day) or parenteral 1000 µg protocols under medical supervision.
- While excess B12 is usually excreted, observational studies have raised unresolved signals linking very high intake to higher lung cancer risk in male smokers, so clinicians should individualize high‑dose use and monitor patients closely.