Most mouth ulcers are a one-off, caused by a bitten cheek, a scratch from sharp food or a stressful week. When ulcers keep coming back, though, it is worth asking whether something else is going on. One known trigger is a shortage of certain nutrients.
Nutrients linked to mouth ulcers
The NHS lists a lack of iron, zinc, folic acid (folate), vitamin B12 or vitamin D among the triggers for mouth ulcers. The Mayo Clinic also names low vitamin B12, zinc, folate and iron as possible causes.
These nutrients help the body make healthy cells, including the cells that line the mouth, which the body replaces very quickly. When levels run low, the lining can become sore and break down more easily.
Other signs to look for
On their own, mouth ulcers rarely point to a deficiency. They mean more when they come with other signs:
- Vitamin B12 or folate: the NHS describes a sore, red tongue, sometimes with mouth ulcers, together with tiredness, weakness, breathlessness and headaches. Low B12 can also cause pins and needles, or problems with memory or balance.
- Iron: the NHS lists a sore tongue and painful sores at the corners of the mouth, along with tiredness, pale skin, breathlessness, headaches and a racing or fluttering heart.
Who is more likely to run low?
- People who eat little meat, fish, eggs or dairy, who may run low on vitamin B12 in particular.
- Women with heavy periods and women who are pregnant, who may run low on iron.
- People with some gut conditions that affect how nutrients are absorbed, such as coeliac disease or Crohn's disease. The NHS also links both of these with mouth ulcers.
- People who have taken certain medications for a long time. A pharmacist can tell you whether yours might matter.
Food first, and a blood test before tablets
A varied diet is the usual way to get these nutrients:
- Iron: red meat, beans and lentils, dark green leafy vegetables, dried fruit and fortified cereals.
- Vitamin B12: meat, fish, eggs, milk and cheese, and fortified foods.
- Folate: green vegetables, chickpeas, beans and fortified cereals.
- Zinc: meat, shellfish, dairy, bread and cereal products.
If you think you may be short of a nutrient, do not start vitamin or mineral tablets on a guess. A doctor can check with a simple blood test and find the cause. Some of these products, including iron, can be harmful in large amounts. Always keep iron tablets out of the reach of children.
When to see a doctor or dentist
See a doctor if your mouth ulcers keep coming back, or if you also notice tiredness, pale skin, breathlessness, a sore red tongue or pins and needles. A blood test can show whether a deficiency is the cause.
See a doctor or dentist sooner if an ulcer:
- lasts more than 3 weeks;
- is larger than usual, or looks different from ulcers you have had before;
- bleeds, or becomes more painful and red;
- comes with a fever or ulcers elsewhere on the body, or with painful or swollen joints.