Exploring the Connection: Can Low B12 Cause Chronic Cough?

October 19, 2025 •

4 min read

Studies suggest that a significant percentage of chronic cough cases remain unexplained, even after an extensive medical workup. Emerging research indicates that a vitamin B12 deficiency may contribute to this phenomenon, raising the question: Can low B12 cause chronic cough? This connection involves sensory neuropathy, a condition that impacts the nervous system.

Quick Summary

Vitamin B12 deficiency may contribute to chronic cough by inducing sensory neuropathy that affects the vagus nerve and increases airway sensitivity. This article examines the link, common deficiency symptoms, and other causes of chronic cough to aid in diagnosis and treatment.

Key Points

Low B12 can cause sensory neuropathy: A B12 deficiency can damage the nerves, including the vagus nerve, leading to airway hypersensitivity that triggers a chronic cough.
A confirmed neurological link: Studies on patients with unexplained chronic cough have shown improvement in symptoms following B12 supplementation.
Other neurological symptoms often present: Chronic cough from B12 deficiency is frequently accompanied by other symptoms like fatigue, numbness, and cognitive issues.
Diagnosis requires specific blood tests: Beyond standard B12 levels, MMA and homocysteine tests can confirm a functional deficiency, especially in borderline cases.
Treatment is effective: For a confirmed deficiency, B12 supplements (oral or injections) can resolve the associated chronic cough and other symptoms.
Rule out other common causes first: It is essential for a doctor to exclude more common causes of chronic cough, such as GERD, asthma, and postnasal drip.
Dietary intake and absorption are key factors: B12 is found in animal products, so dietary intake and malabsorption conditions like pernicious anemia must be considered.

The Neurological Connection: How B12 Deficiency Can Trigger a Chronic Cough

For many individuals, the cause of a persistent cough is traced back to common culprits like postnasal drip, asthma, or acid reflux. However, a subset of patients presents with what is known as 'unexplained chronic cough,' a condition that traditional treatments fail to resolve. Research has identified a fascinating, albeit less common, cause: a deficiency in vitamin B12.

The link is rooted in vitamin B12's crucial role in maintaining nervous system health. Specifically, a B12 deficit can lead to sensory neuropathy, a condition characterized by nerve damage or dysfunction. In the context of chronic cough, this neuropathy can affect the vagus nerve, which transmits sensory information from the airways to the brain. When the vagus nerve is compromised, it can lead to increased airway hypersensitivity.

A key mechanism identified in studies is the upregulation of Nerve Growth Factor (NGF) in the airway mucosa of B12-deficient patients. NGF plays a role in neurogenic inflammation and can sensitize nerve endings. This leaves the pharynx and larynx hyper-responsive to irritants, causing a persistent cough reflex. A study published in the American Journal of Clinical Nutrition showed that patients with B12 deficiency and unexplained chronic cough experienced significant improvement in their symptoms after B12 supplementation.

Understanding the Broad Symptoms of Vitamin B12 Deficiency

While chronic cough can be a manifestation, it is typically not the only sign of a B12 deficiency. Symptoms often develop gradually and can affect both neurological and hematological systems.

Common neurological symptoms include:

Tingling or numbness (pins and needles) in the hands and feet.
Muscle weakness and balance problems, potentially affecting walking (ataxia).
Memory loss, confusion, and difficulty concentrating.
Mood changes, such as irritability or depression.
Vision problems.

Common hematological symptoms (due to anemia) include:

Persistent and overwhelming fatigue.
Pale or yellowish skin.
Weakness.
Shortness of breath and dizziness, especially with exertion.
Sore or tender tongue (glossitis).

Differentiating B12-Related Cough from Other Causes

It is crucial to recognize that a chronic cough has many possible causes, and B12 deficiency is considered a less common one. Other common conditions must be ruled out by a healthcare professional before considering a nutritional cause.

Table: Comparing B12-Related Chronic Cough with Common Causes


Feature	B12 Deficiency-Related Cough	Postnasal Drip	Asthma	GERD	ACE Inhibitors
Mechanism	Sensory neuropathy of the vagus nerve leading to airway hypersensitivity.	Mucus drips down the throat, irritating airways.	Airway inflammation and constriction trigger coughing.	Stomach acid refluxes into the esophagus, causing irritation.	A chemical side effect of the medication.
Associated Symptoms	Fatigue, weakness, anemia, tingling, numbness, memory issues.	Throat clearing, tickle in throat, nasal congestion.	Wheezing, shortness of breath, chest tightness.	Heartburn, bad taste in mouth, hoarseness.	Typically an isolated cough, often dry.
Diagnosis	Blood tests (B12, MMA, homocysteine), ruling out other causes.	Physical exam, allergy testing, sinus imaging.	Pulmonary function tests.	Upper endoscopy, pH monitoring, trial of medication.	Reviewing medication history.
Treatment	B12 supplementation (oral or injections).	Decongestants, antihistamines, nasal steroids.	Inhaled corticosteroids, bronchodilators.	Proton pump inhibitors, lifestyle changes.	Discontinuing or switching the medication.

Diagnosis and Treatment of B12 Deficiency

Diagnosing a B12 deficiency typically starts with a blood test to check serum B12 levels. If levels are low or borderline, a doctor may order additional tests for methylmalonic acid (MMA) and homocysteine. Elevated levels of these metabolic byproducts can confirm a functional deficiency, even if serum B12 is in the low-normal range.

Once a diagnosis is confirmed, treatment is straightforward and highly effective. The method depends on the severity of the deficiency and the underlying cause. For mild cases or dietary deficiencies, high-dose oral B12 supplements may be prescribed. In more severe cases or for individuals with malabsorption issues like pernicious anemia, regular B12 injections are the standard treatment. These injections are often needed indefinitely to prevent symptoms from returning.

Dietary Sources of Vitamin B12

For those at risk of or with a mild B12 deficiency, dietary adjustments can play a supportive role. Since B12 is predominantly found in animal products, vegans and strict vegetarians are at a higher risk.

Foods rich in vitamin B12 include:

Meat and Poultry: Beef liver, beef, and chicken are excellent sources.
Fish and Seafood: Salmon, trout, tuna, and clams are packed with B12.
Dairy Products: Milk, yogurt, and cheese contain good amounts of B12.
Eggs: A solid source of B12, especially in the yolk.
Fortified Foods: Many cereals, plant-based milks, nutritional yeast, and bread are fortified with B12.

Conclusion

In conclusion, while not a mainstream cause, low B12 can indeed cause chronic cough, particularly in cases where other common etiologies have been ruled out. The link is tied to B12's critical role in nerve function, where a deficiency can lead to sensory neuropathy of the vagus nerve and increased airway hypersensitivity. If you have an unexplained chronic cough, especially with other neurological symptoms like tingling or fatigue, it is worth discussing the possibility of a B12 deficiency with your doctor. A simple blood test can determine if this nutritional issue is the root cause, paving the way for a straightforward and effective treatment plan. For more information, the National Institutes of Health provides extensive resources on vitamin B12 deficiency.

Seeking Professional Guidance

It is important to seek medical advice for any persistent health issues. A chronic cough is a symptom, not a diagnosis, and requires a thorough evaluation to identify the underlying cause. While low B12 is a possible factor, a physician can help rule out more common or serious conditions and ensure the correct treatment is prescribed.

Frequently Asked Questions

B12 deficiency can cause sensory neuropathy of the vagus nerve, which transmits signals from the airways. This makes the airways hypersensitive to irritants, triggering a persistent cough reflex.

Common causes include postnasal drip (upper airway cough syndrome), asthma, gastroesophageal reflux disease (GERD), smoking, certain medications like ACE inhibitors, and underlying lung conditions like COPD.

Yes, vitamin B12 deficiency can cause neurological symptoms, including peripheral neuropathy, even before megaloblastic anemia develops. This is why it is often called a 'functional' deficiency.

Diagnosis begins by first ruling out other common causes. If a neurological cause is suspected, blood tests for B12, methylmalonic acid (MMA), and homocysteine are used to confirm a deficiency.

Treatment involves B12 supplementation. The form (oral pills or intramuscular injections) and duration depend on the severity and underlying cause, such as malabsorption issues.

In studies, patients with B12 deficiency-related cough saw improvements in histamine-triggered cough thresholds after two months of weekly B12 injections. However, individual response times can vary.

Risk factors include following a vegan or vegetarian diet, being over 65, having a history of gastrointestinal surgery, and having conditions like pernicious anemia, celiac disease, or Crohn's disease.