Mouth ulcers and nutrient deficiencies: when B12 or folate matters

A nutritional cause is possible

NHS guidance includes mouth ulcers among possible B12 or folate deficiency symptoms. Assessment can combine history, examination and blood testing. An ulcer alone cannot distinguish between these deficiencies or show whether absorption, diet or another issue is involved. [1]

Many ulcers have a local explanation

Cheek biting, a sharp tooth, poorly fitting dental appliances and irritation can cause ulcers. Multiple or recurrent lesions can have other explanations too. Treating a confirmed deficiency is different from assuming every sore needs a B-vitamin tablet. [2]

Use the healing time as a review point

NHS advises seeing a dentist or doctor for an ulcer lasting more than three weeks, or one that is unusual, bleeds or becomes more painful. Imagine a sore stays in the same place despite supplements: have it examined instead of repeatedly changing vitamin brands. [2]

Hypothetical example — use symptom context rather than guessing a missing vitamin
Situation	Useful distinction
Confirmed B12 or folate deficiency	Treat and investigate the cause
Sharp tooth next to the ulcer	Consider local injury
Ulcer beyond three weeks	Arrange examination

Mouth ulcers and nutrient deficiencies: when B12 or folate matters — original article outline diagram — Original editorial diagram of this article’s sections; no product photograph or clinical finding is depicted.

Sources for this article

Vitamin B12 or folate deficiency anaemia - NHS
Source consulted: 2026-09-20. This is a reference resource, not a claim that we conducted the studies or tested a product.
Mouth ulcers - NHS
Source consulted: 2026-09-20. This is a reference resource, not a claim that we conducted the studies or tested a product.