Yes, vitamin B12 deficiency can cause mouth ulcers: What you need to know

October 8, 2025 •

4 min read

Studies have shown that oral manifestations, including recurring ulcers, can be one of the earliest indicators of a vitamin B12 deficiency, sometimes appearing before other systemic symptoms. The link is rooted in this vitamin's vital role in cell regeneration and immune function, both crucial for maintaining healthy oral tissues.

Quick Summary

Vitamin B12 deficiency can manifest as persistent or recurrent mouth ulcers, along with other oral symptoms like a red tongue and burning sensations. These issues arise from impaired cell regeneration and a weakened immune response. Diagnosis and treatment, often involving supplements, are essential.

Key Points

Direct Connection: Vitamin B12 deficiency can directly cause mouth ulcers because it disrupts the rapid cell regeneration needed for healthy oral tissues.
Early Warning Sign: Persistent or frequent mouth ulcers can be an early indicator of a B12 deficiency, sometimes appearing before more common symptoms like fatigue.
Beyond Ulcers: Look for other oral signs of deficiency, including a smooth, red, and painful tongue (glossitis), a burning sensation, and cracks at the corners of the mouth (angular cheilitis).
Multiple Causes: The most common causes are absorption issues (like pernicious anemia), dietary restrictions (vegans), certain medications, and medical conditions.
Treatment Options: Treatment typically involves addressing the underlying cause and may include oral supplements, injections, or dietary adjustments.
Dietary Sources: Increase your intake of animal products like meat, fish, eggs, and dairy, or rely on fortified foods and supplements for plant-based diets.

The Direct Link Between B12 Deficiency and Oral Ulcers

Your oral health can be an early indicator of a systemic issue, and a deficiency in vitamin B12 is a prime example. The connection between a lack of vitamin B12 and mouth ulcers is well-documented in medical and dental literature. Vitamin B12, also known as cobalamin, is essential for DNA synthesis and the formation of red blood cells. Oral tissues, like those lining your mouth, regenerate at one of the fastest rates in your body, making them particularly sensitive to a shortage of B12. When levels are low, this rapid cell turnover is disrupted, leading to inflammation and the formation of painful mouth ulcers, also known as aphthous ulcers or canker sores.

Beyond Mouth Ulcers: Other Oral Symptoms

While mouth ulcers are a key sign, a B12 deficiency can cause several other oral problems that signal a deeper issue. These include:

Glossitis: This condition is characterized by a smooth, swollen, and unusually red tongue due to the loss of normal papillae. The tongue can also feel sore or painful.
Glossodynia (Burning Mouth Syndrome): Many people with low B12 levels report a persistent burning or tingling sensation in their mouth or tongue, even if the mucosa appears normal.
Angular Cheilitis: This causes painful, inflamed cracks at the corners of the mouth that may heal slowly.
Gum Sensitivity: A lack of B12 can cause gums to become more prone to inflammation, irritation, and bleeding.
Altered Taste (Dysgeusia): Some individuals report a strange or altered taste in their mouth.

Common Causes of Vitamin B12 Deficiency

For many, a lack of dietary intake is not the primary cause, as the body can store B12 for several years. Instead, absorption issues are the main culprit.

Pernicious Anemia: An autoimmune condition where the stomach cannot produce intrinsic factor, a protein required for B12 absorption. This is one of the most common causes, especially in adults.
Dietary Factors: Vegans and strict vegetarians are at a higher risk since B12 is found almost exclusively in animal products. Those on a plant-based diet must rely on fortified foods or supplements to meet their needs.
Medical Conditions: Diseases affecting the small intestine, such as Crohn's disease or celiac disease, can impair absorption. Stomach surgeries, like gastrectomy, also impact the ability to absorb B12.
Medications: Certain drugs, including long-term use of proton pump inhibitors (PPIs) for acid reflux and metformin for type 2 diabetes, can interfere with B12 absorption.
Age: Older adults may experience a thinning of the stomach lining, leading to decreased acid production and poor B12 absorption.

Diagnosis and Treatment of B12 Deficiency-Related Ulcers

To confirm a B12 deficiency, a healthcare provider will typically order a blood test to check your serum vitamin B12 levels. Early diagnosis is crucial, as some complications from long-term deficiency can be irreversible.

Treatment focuses on restoring B12 levels and may include:

Supplements: For many, high-dose oral B12 supplements (e.g., 1,000 micrograms daily) can be effective, even for those with absorption issues like pernicious anemia, due to a passive absorption pathway.
Injections: In severe cases or for rapid correction, intramuscular injections of B12 are administered to bypass any absorption problems.
Dietary Adjustments: Increasing intake of B12-rich foods is a key part of long-term management. For vegans, ensuring intake of fortified foods or consistent supplementation is vital.
Symptom Management: While addressing the underlying deficiency, topical oral gels or antimicrobial mouthwashes can help manage the pain and irritation of existing mouth ulcers.

Comparison of Mouth Ulcer Types

It's important to distinguish ulcers caused by deficiency from other types, which can have different causes and characteristics.


Feature	B12 Deficiency Ulcers	Canker Sores (Idiopathic Aphthous)	Cold Sores (Herpes Simplex)
Cause	Impaired cell regeneration from B12/nutrient deficiency.	Unknown, often triggered by stress, minor injury, or hormonal changes.	Caused by the herpes simplex virus (HSV-1), which is contagious.
Location	Can appear anywhere inside the mouth, including cheeks, tongue, and gums.	Occur on the soft, movable tissues inside the mouth.	Typically appear as blisters on the lips or outside the mouth.
Appearance	White, yellow, or greyish lesions with a red border.	Small, round or oval, with a white or yellow center and a red border.	Clusters of small, fluid-filled blisters that can burst and crust over.
Recurrence	Often frequent and may indicate an underlying issue requiring medical attention.	Can be recurrent, though the cause is often non-nutritional.	Can recur in the same spot, triggered by stress or illness.
Contagious	Not contagious.	Not contagious.	Highly contagious.

Dietary Sources of Vitamin B12

Incorporating B12-rich foods into your diet is essential for prevention and management.

Meat and Poultry: Beef, chicken, and other meats are excellent sources of naturally occurring vitamin B12.
Fish and Seafood: Clams, salmon, tuna, and oysters are especially high in B12.
Dairy Products: Milk, cheese, and yogurt provide good amounts of B12.
Eggs: A reliable source for those who eat eggs.
Fortified Foods: Many breakfast cereals, plant-based milks, and nutritional yeast products are fortified with B12, making them vital for vegan diets.

Conclusion

Vitamin B12 deficiency can indeed cause mouth ulcers and a host of other painful oral symptoms due to its fundamental role in cell regeneration and immune function. As these oral signs can often precede other systemic issues, they are a valuable early warning sign that should not be ignored. Proper diagnosis by a healthcare professional is key to determining the underlying cause and establishing an appropriate treatment plan, which may include dietary changes, oral supplements, or injections. Maintaining adequate B12 levels through a balanced diet or supplementation is the best way to prevent the recurrence of these unpleasant and painful oral issues. If you experience persistent or recurrent mouth ulcers, it is advisable to speak with a doctor or dentist to get your B12 levels checked.

Frequently Asked Questions

The terms are often used interchangeably, but a mouth ulcer is a broad term for any oral sore. Canker sores are a type of mouth ulcer. Ulcers caused by a B12 deficiency are specifically linked to a nutritional shortage, whereas canker sores can have many triggers.

Without addressing the underlying deficiency, these ulcers may recur or persist. Once B12 levels are restored through proper treatment, healing can be expected within one to two weeks, similar to other types of minor ulcers.

Yes, a lack of vitamin B12 can increase the risk of inflammation and irritation, making gums more susceptible to bleeding and gum disease.

In some cases, yes. A few studies have documented oral symptoms like glossodynia (burning mouth) in patients with B12 deficiency whose oral mucosa appeared normal.

Vegans can prevent deficiency by consuming fortified foods like cereals, plant-based milks, and nutritional yeast. Taking a high-quality B12 supplement is also a reliable way to ensure adequate intake.

Focus on consuming foods rich in vitamin B12, such as meat, fish, eggs, and dairy. For immediate relief and to aid healing, avoid spicy, acidic, or hard foods that can irritate the sores, and stick to softer options.

If mouth ulcers are persistent, large, unusually painful, or accompanied by other symptoms like fatigue, numbness, or a burning sensation, you should consult a doctor or dentist. They can determine if a B12 deficiency or another underlying condition is the cause.