Low intake and malabsorption are different routes
People following diets without reliable animal or B 12-fortified foods can have inadequate intake. Autoimmune gastritis, reduced intrinsic-factor function, some intestinal disorders and gastrointestinal surgery can impair absorption even when food intake appears adequate. Older adults may have several contributing factors at once. [1]
Include medicines and infant nutrition
Metformin and gastric-acid-suppressing medicines can affect B 12 status. Infants breastfed by mothers with inadequate B 12 status are also at risk; infant symptoms require prompt clinical assessment. These examples do not mean every person in a group becomes deficient or should receive the same supplement dose. [1]
A risk history guides assessment
Imagine an older adult eats animal foods but has had gastric surgery and takes metformin. The food history does not cancel the other risks. New numbness, unexplained fatigue or other concerning symptoms should be assessed; neurological B 12 problems can occur without anemia. Record the surgery, medicines, diet and supplements rather than using one factor as the diagnosis. [1]
| Hypothetical history | Question it raises |
|---|---|
| Vegan diet without fortified foods | Reliable B 12 intake |
| Gastric or ileal surgery | Absorption and replacement route |
| Metformin plus new neurological symptoms | Assessment rather than assumption |
Sources for this article
- Vitamin B12 - Health Professional Fact Sheet
Source consulted: 2026-09-20. This is a reference resource, not a claim that we conducted the studies or tested a product.