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Anemia of B12 Deficiency (Pernicious Anemia) 

 What is vitamin B12 deficiency anemia?

Vitamin B12 deficiency anemia is one of several types of megaloblastic anemia. Megaloblastic anemia is a type of anemia characterized by very large red blood cells. In addition to the cells being large, the inner contents of each cell are not completely developed. This malformation causes the bone marrow to produce fewer cells, and sometimes the cells die earlier than the 120-day life expectancy. Instead of being round or disk-shaped, the red blood cells can be oval. Vitamin B12 deficiency anemia and folate deficiency anemia are the most common causes of megaloblastic anemia. Pernicious anemia is a subtype of B12 deficiency. 

What causes vitamin B12 deficiency anemia?

Vitamin B12 deficiency anemia is more common in individuals of northern European descent. The condition is caused by one of the following:

  • Vitamin B12 deficiency caused by a lack of intrinsic factor in gastric (stomach) secretions--intrinsic factor is necessary for absorption of vitamin B12. This type of B12 deficiency anemia is technically pernicious anemia.

  • Vitamin B12 deficiency caused by surgery that removes or bypasses the end of the small intestine where vitamin B12 is absorbed. This type should not, technically, be called pernicious anemia, but some people will use this name for all kinds of anemia due to vitamin B12 deficiency. 

The inability to make intrinsic factor may be the result of several factors, such as chronic gastritis, gastrectomy (removal of all or part of the stomach), or an autoimmune condition (the body attacks its own tissues). Other types of megaloblastic anemia may be associated with type 1 diabetes, thyroid disease, and a family history of the disease.

What are the symptoms of vitamin B12 deficiency anemia?

The following are the most common symptoms for megaloblastic anemia. However, each individual may experience symptoms differently. Symptoms may include:

  • Weak muscles

  • Numbness or tingling in hands and feet

  • Difficulty walking

  • Nausea

  • Decreased appetite

  • Weight loss

  • Irritability

  • Lack of energy or tiring easily (fatigue)

  • Diarrhea

  • Smooth and tender tongue

  • Increased heart rate (tachycardia)

The symptoms of megaloblastic anemia may resemble other blood conditions or medical problems. Always consult your doctor for a diagnosis.

How is vitamin B12 deficiency anemia diagnosed?

This type of anemia is usually discovered during a medical examination through a routine blood test. In addition to a complete medical history and physical examination, diagnostic procedures for megaloblastic anemia may include additional blood tests and other evaluation procedures, including the Schilling test.

The Schilling test is performed to detect vitamin B12 absorption. In the Schilling test, vitamin B12 levels are measured in the urine after the ingestion of radioactive vitamin B12. With normal absorption, the ileum (portion of the small intestine) absorbs more vitamin B12 than the body needs and excretes the excess into the urine. With impaired absorption, however, little or no vitamin B12 is excreted into the urine. When impaired absorption is the result, a second Schilling test can be performed with ingestion of intrinsic factor with the radioactive B12 to determine if the problem is due to intrinsic factor production or absorption at the ileum. 

Treatment for vitamin B12 deficiency anemia

Specific treatment for vitamin B12 deficiency anemia will be determined by your doctor based on:

  • Your age, overall health, and medical history

  • Extent of the disease

  • Your tolerance for specific medications, procedures, or therapies

  • Expectations for the course of the disease

  • Your opinion or preference

Vitamin B12 deficiency anemia and folate deficiency anemia often occur together and can be difficult to tell apart. Treatment may include vitamin B12 injections and folic acid pills. Foods that are rich in folic acid include the following:

  • Orange juice

  • Oranges

  • Romaine lettuce

  • Spinach

  • Liver

  • Rice

  • Barley

  • Sprouts

  • Wheat germ

  • Soy beans

  • Green, leafy vegetables

  • Beans

  • Peanuts

  • Broccoli

  • Asparagus

  • Peas

  • Lentils

  • Chickpeas (garbanzo beans)

Foods that are rich in folic acid and vitamin B12 include the following:

  • Eggs

  • Meat

  • Poultry

  • Milk

  • Shellfish

  • Fortified cereals

Taking folic acid by mouth is more effective than eating foods rich in folic acid. B12 is not as well absorbed by mouth as per injection.