What is a vitamin B12 deficiency disease known as?

December 6, 2025 •

4 min read

The human body does not produce vitamin B12, but an inability to absorb it is the most common cause of a specific vitamin B12 deficiency disease known as pernicious anemia. This autoimmune condition leads to a depletion of a vital nutrient and can cause widespread health issues if left unaddressed.

Quick Summary

Pernicious anemia is the most common cause of vitamin B12 deficiency, resulting in a type of megaloblastic anemia due to poor absorption. Consequences can affect neurological and hematological systems.

Key Points

Pernicious Anemia: The most common disease known as a vitamin B12 deficiency, it is an autoimmune condition that prevents absorption.
Megaloblastic Anemia: A condition resulting from B12 deficiency where red blood cells are abnormally large and don't function properly.
Key Symptoms: Symptoms include fatigue, pale skin, glossitis (red tongue), neurological issues like pins and needles, and cognitive changes.
Common Causes: Malabsorption due to autoimmune conditions, gastrointestinal surgery, or intestinal disorders are common causes, as are certain medications and strict vegan diets.
Diagnosis is Key: Diagnosis relies on blood tests for B12 levels and specific antibodies, as symptoms can be vague and develop slowly.
Lifelong Treatment: Treatment for pernicious anemia and other malabsorption issues often requires lifelong B12 supplementation, usually via injections or high-dose oral tablets.

Introduction to Pernicious Anemia

While the general term for a lack of vitamin B12 is simply "vitamin B12 deficiency," the most common disease associated with it is pernicious anemia. This is a specific type of megaloblastic anemia that results from the body's inability to properly absorb vitamin B12 from the digestive tract. The term "pernicious" historically meant harmful or deadly, reflecting the disease's once-fatal prognosis before vitamin B12 treatments were discovered. Today, it is manageable with proper medical care.

The Role of Intrinsic Factor

The root cause of pernicious anemia lies in the stomach, specifically with a protein called intrinsic factor. Normally, cells in the stomach lining produce this protein, which then binds to vitamin B12 from food. This newly formed complex travels to the small intestine where it can be absorbed into the bloodstream. In pernicious anemia, the immune system mistakenly attacks the very cells that produce this intrinsic factor. Without intrinsic factor, vitamin B12 cannot be absorbed, regardless of how much is consumed.

The Connection to Megaloblastic Anemia

Vitamin B12 is critical for the production of healthy red blood cells. When a deficiency occurs, it disrupts the DNA synthesis required for new blood cells to form correctly. As a result, the bone marrow produces abnormally large, immature red blood cells called megaloblasts, which are often oval-shaped instead of round. These oversized cells are not fully functional and die prematurely, leading to a shortage of healthy red blood cells and causing the symptoms of anemia. While pernicious anemia is a cause of megaloblastic anemia, other factors can also lead to this condition.

Recognizing the Symptoms of B12 Deficiency

Symptoms of a vitamin B12 deficiency can vary widely and often develop gradually over several years, making diagnosis difficult. A comprehensive list of symptoms includes:

Physical: Extreme fatigue or weakness, shortness of breath, pale skin, a sore or red tongue (glossitis), mouth ulcers, and weight loss.
Neurological: Pins and needles (paraesthesia) or numbness in the hands and feet, memory loss, confusion, vision problems, difficulty with balance, and walking issues.
Psychological: Mood changes, irritability, depression, anxiety, and, in severe cases, impaired cognitive function or dementia.

Common Causes Beyond Pernicious Anemia

While pernicious anemia is the leading cause of B12 deficiency in some regions, several other factors can lead to the condition. These include:

Dietary Factors: Individuals who follow a strict vegan or vegetarian diet are at risk if they do not consume fortified foods or supplements, as natural vitamin B12 is primarily found in animal products.
Gastrointestinal Surgery: Procedures such as gastric bypass or partial removal of the stomach or small intestine can interfere with B12 absorption.
Intestinal Disorders: Conditions like Crohn's disease, celiac disease, and bacterial overgrowth can hinder B12 absorption in the intestines.
Medications: Certain drugs, including the diabetes medication metformin and long-term use of proton pump inhibitors, can reduce B12 absorption.
Chronic Alcohol Use: Excessive alcohol consumption can damage the digestive system and lead to a deficiency.
Aging: Older adults may have decreased stomach acid, which affects the release of B12 from food for absorption.

Diagnosing Vitamin B12 Deficiency and its Cause

Diagnosing the underlying cause of vitamin B12 deficiency is crucial for determining the correct treatment plan, as individuals with pernicious anemia will require lifelong treatment. A healthcare provider will typically perform several tests, which may include blood tests to check vitamin B12 levels, a complete blood count (CBC) to identify signs of megaloblastic anemia, and tests for specific antibodies to confirm pernicious anemia.

Comparing Treatment for B12 Deficiency

Treatment for B12 deficiency primarily involves supplementation, with the method depending on the underlying cause. The following table compares common treatment options.


Feature	Intramuscular Injections	High-Dose Oral Supplements
Best For	Severe deficiency, confirmed malabsorption issues (like pernicious anemia), or neurological symptoms.	Mild deficiency or dietary-related causes. Also an option for pernicious anemia based on some studies.
Effectiveness	Leads to rapid replacement and improvement, especially with neurological symptoms.	Can be as effective as injections for correcting anemia, though some markers may not improve as well.
Administration	Administered by a doctor or nurse, with the possibility of self-administering monthly shots for maintenance.	Taken by mouth, usually daily initially, then less frequently.
Duration	Lifelong treatment is typically needed for pernicious anemia and other malabsorption issues.	Lifelong for chronic conditions; shorter term for dietary correction.

The Dangers of Untreated Deficiency

If a vitamin B12 deficiency is left untreated, the health consequences can be severe and potentially irreversible. Neurological damage is a serious risk, leading to persistent numbness, tingling, cognitive issues, and permanent disability. Severe anemia can also strain the heart, increasing the risk of cardiovascular problems. The potential complications highlight the importance of early diagnosis and consistent treatment.

Conclusion: Seeking Medical Advice is Crucial

The most specific disease known as a vitamin B12 deficiency is pernicious anemia, an autoimmune condition causing malabsorption. This leads to megaloblastic anemia, characterized by abnormal red blood cells. Symptoms can range from fatigue and neurological issues to psychological problems. While dietary insufficiency is a cause, malabsorption is more common, especially in older adults. Treatment typically involves vitamin B12 supplementation, often lifelong for pernicious anemia. If you experience any persistent symptoms, consulting a healthcare provider for proper diagnosis and treatment is essential to prevent irreversible complications. You can find more information about this and other types of anemia from authoritative sources such as the National Heart, Lung, and Blood Institute (NHLBI) at NIH.

Frequently Asked Questions

The primary disease associated with vitamin B12 deficiency, and its most common cause in some regions, is pernicious anemia. This is an autoimmune condition that affects vitamin B12 absorption.

Megaloblastic anemia is the hematological condition caused by vitamin B12 deficiency (or folate deficiency), where the body produces abnormally large, immature red blood cells that cannot function correctly.

Pernicious anemia is an autoimmune disorder in which the body's immune system attacks and destroys the stomach cells that produce intrinsic factor, a protein necessary for absorbing vitamin B12 from food.

Common neurological symptoms include tingling or numbness in the hands and feet, memory problems, confusion, vision issues, and difficulty with walking or balance.

For severe deficiency or absorption issues like pernicious anemia, intramuscular injections are traditionally used for rapid replacement. However, high-dose oral supplements can be equally effective in many cases.

Yes. Vitamin B12 is found naturally in animal products, so individuals on strict vegan or vegetarian diets are at high risk of deficiency if they don't consume fortified foods or take supplements.

While many symptoms can be reversed with treatment, neurological damage that has lasted for months or years can sometimes become permanent. This is why early diagnosis and treatment are crucial.

Untreated B12 deficiency can lead to severe and potentially permanent neurological damage, including memory loss and difficulty walking. Severe anemia can also strain the heart.