Can Low B12 Cause a Sour Taste in the Mouth?

October 13, 2025 •

3 min read

According to the National Institutes of Health, vitamin B12 deficiency can lead to a variety of oral issues, including an altered sense of taste. This phenomenon, known as dysgeusia, can manifest as a persistent, unpleasant flavor, such as a sour or metallic taste in the mouth. The connection lies in how low B12 affects nerve function and the health of the tongue, disrupting the way taste is perceived.

Quick Summary

Low B12 can cause an altered sense of taste, or dysgeusia, which can include a sour or metallic flavor. The deficiency impacts nerve function and red blood cell production, leading to oral health problems like glossitis and tongue pain that disrupt normal taste perception. Timely diagnosis and supplementation are key to resolving these oral symptoms.

Key Points

Dysgeusia: Low B12 can cause an altered sense of taste (dysgeusia), which can present as a sour, metallic, or bitter flavor.
Glossitis: Inflammation and loss of taste buds on the tongue (glossitis) due to B12 deficiency directly impairs taste perception.
Nerve Function: The vitamin is vital for healthy nerve tissue; a deficiency can affect the cranial nerves that control taste.
Systemic Symptoms: A sour taste is often accompanied by other signs of B12 deficiency, such as fatigue, numbness, and mood changes.
Diagnosis is Key: A persistent change in taste, along with other symptoms, warrants a doctor's visit and blood tests to confirm a B12 deficiency.
Treatment Resolves: Supplementation with oral B12 or injections can effectively reverse oral symptoms and restore normal taste perception.
Oral Health Role: Oral manifestations can sometimes be the first and most prominent signs of a B12 deficiency before anemia develops.

The Link Between B12 and Your Sense of Taste

Vitamin B12 is essential for maintaining healthy nerve tissue and producing red blood cells. A deficiency can disrupt these vital functions. When nerve function is compromised, it can affect the cranial nerves responsible for transmitting taste signals to the brain, leading to a distorted sense of taste known as dysgeusia. This can present as a sour, metallic, bitter, or rancid flavor.

How B12 Deficiency Affects Oral Health

One common oral sign of a B12 deficiency is glossitis, which is the inflammation of the tongue. The tongue can become smooth, swollen, and painful as the papillae (containing taste buds) atrophy. This loss impairs taste bud function, distorting taste. Reduced red blood cell production also decreases oxygen to the tongue, further impacting its health.

Other Oral Symptoms of B12 Deficiency

A sour taste is one of several oral signs. Others include:

Glossodynia: Burning sensation in the tongue or mouth.
Oral ulcers: Sores on gums or tongue.
Cheilitis: Inflammation and cracking at mouth corners.
Lingual paresthesia: Tingling or numb feeling in the tongue.

Beyond the Mouth: Systemic Symptoms

B12 deficiency affects the entire body. Consider symptoms like:

Extreme fatigue and weakness: A classic sign of megaloblastic anemia.
Neurological issues: Numbness or tingling in hands/feet, balance problems, memory issues.
Psychological symptoms: Depression, irritability, mood changes.
Cardiovascular issues: Shortness of breath, heart palpitations.

Comparison Table: Causes of Sour Taste


Cause	How it Causes Sour Taste	Associated Symptoms
B12 Deficiency	Disrupted nerve function and taste bud atrophy.	Fatigue, glossitis, mouth ulcers, numbness in extremities, neurological issues.
Acid Reflux (GERD)	Stomach acid regurgitates into the mouth.	Heartburn, nausea, sore throat, difficulty swallowing.
Poor Oral Hygiene	Bacterial buildup on the tongue and teeth.	Bad breath, bleeding gums (gingivitis), dental infections.
Medications	Certain drugs, like antibiotics or antidepressants, alter taste perception.	Dry mouth (xerostomia), side effects specific to the medication.
Infections	Bacterial, viral, or fungal infections inflame oral tissues.	Oral thrush (white patches), sinus congestion, sore throat.

Diagnosing and Treating a B12 Deficiency

A persistent sour or metallic taste, with other symptoms, warrants seeing a healthcare provider. Diagnosis uses blood tests to measure B12 levels and sometimes homocysteine or methylmalonic acid levels.

Treatment depends on the cause:

Dietary changes: Eat B12-rich foods (meat, fish, dairy, fortified cereals).
Oral supplements: Effective for many, especially those with less severe malabsorption.
B12 injections: For severe deficiencies or malabsorption like pernicious anemia.

Conclusion

A sour taste in the mouth can be a sign of vitamin B12 deficiency, often with glossitis and altered taste. Nerve function and red blood cell production disruption impacts taste buds. Early treatment with supplements or injections can reverse symptoms and prevent neurological damage. While other conditions cause a sour taste, consider B12 deficiency if accompanied by fatigue or other neurological signs for correct diagnosis and treatment.

Lists

Signs of Oral Nerve Disruption from B12 Deficiency

Altered sense of taste (dysgeusia), which may include a sour flavor.
Tingling or numbness in the tongue (lingual paresthesia).
Painful, inflamed tongue (glossitis).
Burning sensation in the mouth (glossodynia).

Best Dietary Sources of Vitamin B12

Animal products: Meat, fish, poultry, eggs, and dairy.
Fortified foods: Many plant-based milks, cereals, and nutritional yeast.
Supplements: Oral tablets, sublingual drops, or injections as prescribed by a doctor.

Common Causes of Dysgeusia (Altered Taste)

Nutritional deficiencies: Especially B12 and zinc.
Medical conditions: GERD, diabetes, or nerve damage.
Medications: Antibiotics, antidepressants, and chemotherapy.
Oral hygiene issues: Gingivitis and infections.

An extensive review on the impact of micronutrients on taste can provide further context on how B12 contributes to taste perception.

Frequently Asked Questions

A B12 deficiency can cause a sour taste due to its impact on the nervous system and oral health. The lack of this vitamin can damage the nerves that control taste and lead to inflammation of the tongue (glossitis), causing taste buds to malfunction and alter the perception of flavor.

Yes, a metallic taste is a well-documented symptom of a B12 deficiency. Like a sour taste, this altered taste sensation is a form of dysgeusia resulting from nerve-related issues and changes to the oral environment caused by the deficiency.

Besides an altered taste, other oral symptoms include glossitis (a sore, swollen, red tongue), a burning sensation in the mouth (glossodynia), and recurrent mouth ulcers.

Once supplementation begins, improvements in oral symptoms, including a sour taste, can occur relatively quickly, often within a few weeks to months. However, the exact timeline depends on the severity of the deficiency and the form of treatment (oral vs. injections).

The primary cause is often malabsorption of the vitamin, most commonly due to a lack of intrinsic factor—a protein needed for B12 absorption. This is a key feature of pernicious anemia, an autoimmune condition.

No, a sour taste can have many causes, including acid reflux (GERD), poor oral hygiene, certain medications, or other nutritional deficiencies like zinc. It is important to consult a doctor for a proper diagnosis.

Dietary changes can help prevent a B12 deficiency in those with inadequate intake. However, for most individuals who experience taste issues due to a deficiency, the problem is malabsorption, requiring supplementation via high-dose oral tablets or injections under medical supervision.