Anemia is a medical condition in which the blood is low in normal red blood cells. Pernicious anemia is one of the vitamin B-12 deficiency anemias. It’s caused by an inability to absorb the vitamin B-12 needed for your body to make enough healthy red blood cells.

Pernicious anemia is a rare condition, with a prevalence of .1 percent in the general population and 1.9 percent in people who are older than 60 years, according to a 2012 study in the Journal of Blood Medicine.

This type of anemia is called “pernicious” because it was once considered a deadly disease. This was due to the lack of available treatment.

Today, though, the disease is relatively easy to treat with B-12 injections or supplements. However, if left untreated, vitamin B-12 deficiency can lead to severe complications.

The progression of pernicious anemia is slow. It may be difficult to recognize the symptoms because you may have become used to not feeling well.

Commonly overlooked symptoms include:

In rare cases of pernicious anemia, people may have neurological symptoms. These can include:

Other symptoms of a B-12 deficiency, which can overlap with pernicious anemia, include:

Lack of vitamin B-12

People with anemia have low levels of normal red blood cells (RBCs). Vitamin B-12 plays a role in creating RBCs, so the body requires an adequate intake of vitamin B-12. Vitamin B-12 is found in:

  • meat
  • poultry
  • shellfish
  • eggs
  • dairy products
  • fortified soy, nut, and rice milks
  • nutritional supplements

Lack of IF

Your body also needs a type of protein called intrinsic factor (IF) to absorb vitamin B-12. IF is a protein produced by cells in the stomach. After you consume vitamin B-12, it travels to your stomach where it binds with IF. The two are then absorbed in the last part of your small intestine.

In most cases of pernicious anemia, the body’s immune system attacks and destroys the cells that produce IF in the stomach. If these cells are destroyed, the body can’t make IF and can’t absorb vitamin B-12 found in foods such as those listed above.


Without enough vitamin B-12, the body will produce abnormally large red blood cells called macrocytes. Because of their large size, these abnormal cells may not be able to leave the bone marrow, where red blood cells are made, and enter the bloodstream. This decreases the amount of oxygen-carrying red blood cells in the bloodstream and can lead to fatigue and weakness.

Pernicious anemia is a type of macrocytic anemia. It’s sometimes called megaloblastic anemia because of the abnormally large size of the red blood cells produced.

Pernicious anemia is not the only kind of macrocytic anemia. Other causes of abnormally large red blood cells include:

Other vitamin B-12 deficiencies, such as those caused by poor diet, are often confused with pernicious anemia. Pernicious anemia is strictly an autoimmune disorder. It results from a lack of IF and poor B-12 absorption.

This vitamin deficiency can be treated by altering your diet or adding a B-12 supplement or B-12 injection to your healthcare regimen.

In people with B-12 deficiencies or regular anemia, the body can absorb B-12. On the other hand, someone with pernicious anemia struggles to do so. Pernicious anemia is also seen in children who are born with a genetic defect that prevents them from making IF.

Some individuals are more likely than others to develop pernicious anemia. Risk factors include:

  • having a family history of the disease
  • being of Northern European or Scandinavian descent
  • having type 1 diabetes, an autoimmune condition, or certain intestinal diseases such as Crohn’s disease
  • having had part of your stomach or intestines removed
  • being 60 years or older
  • being strictly vegetarian and not taking a B-12 supplement

Your risk of developing pernicious anemia also increases as you get older.

Your doctor will usually need to do several tests to diagnose you with pernicious anemia. These include:

  • Complete blood count. This test measures vitamin B-12 and iron levels in blood serum.
  • Vitamin B-12 deficiency test: Your doctor can assess your vitamin B-12 levels through a blood test. Low levels indicate a deficiency.
  • Biopsy. Your doctor may also want to see if there has been any damage to your stomach walls. They can diagnose this through a biopsy. The biopsy involves removing a sample of the stomach’s cells. The cells are then examined microscopically for any damage.
  • IF deficiency test. Intrinsic factor deficiency is tested through a blood sample. The blood is tested for antibodies against IF and the stomach’s cells.

In a healthy immune system, antibodies are responsible for finding bacteria or viruses. They then mark the invading germs for destruction.

In an autoimmune disease such as pernicious anemia, the body’s antibodies stop distinguishing between diseased and healthy tissue. In this case, the antibodies destroy the cells making IF.

The treatment for pernicious anemia is a two-part process. Your doctor will treat any existing vitamin B-12 deficiency and check for iron deficiency.

Treatment begins with:

  • vitamin B-12 injections that are slowly decreased over time
  • complete blood counts to measure vitamin B-12 and iron levels in blood serum
  • blood tests to monitor replacement treatments

Vitamin B-12 injections can be given daily or weekly until the B-12 levels return to normal (or close to normal). During the first few weeks of treatment, your doctor may recommend limiting physical activity.

After your vitamin B-12 levels are normal, you’ll only need to get the shot once per month. You can administer the shots yourself or have someone else give them to you at home to save you trips to the doctor.

After your B-12 levels are normal, your doctor may recommend you take regular doses of B-12 supplements instead of the injection. These come in pills, nasal gels, and sprays.

Your doctor may want to monitor you on a long-term basis. This will help them identify possible serious effects of pernicious anemia. The most dangerous complication is gastric cancer. They can check for the start of cancer at regular visits and through biopsies.

Other potential complications of pernicious anemia include:

  • nerve damage
  • digestive tract problems
  • memory problems, confusion, or other neurological symptoms
  • heart damage

These complications most often stem from long-lasting pernicious anemia. They can be permanent.

Many people with pernicious anemia require lifelong treatment and monitoring. This can help prevent long-term damage. The symptoms of long-term damage include:

Talk to your doctor if you think you may have symptoms of pernicious anemia. Early diagnosis, treatment, and close monitoring are important for preventing any future problems.