Pernicious Anemia

Pernicious anemia, one of the causes of vitamin B12 deficiency, is an autoimmune condition that prevents your body from absorbing vitamin B12. Left untreated, pernicious anemia can cause serious medical issues, including irreversible damage to your nervous system.


Woman drinking liquid with inset of digestive system (center). Detail on normal and abnormal B-12 absorption process (left).
Woman drinking liquid with inset of digestive system (center) and (left) detail on normal and abnormal B-12 absorption process.

What is pernicious anemia?

Pernicious (per-nish-uhs) anemia, one of the causes of vitamin B12 deficiency, is an autoimmune condition that prevents your body from absorbing vitamin B12. Without adequate vitamin B12, you have fewer red blood cells carrying oxygen throughout your body.

You can have pernicious anemia for several years before noticing changes in your body. Left untreated, pernicious anemia can cause serious medical issues, including irreversible damage to your nervous system. Healthcare providers treat pernicious anemia by prescribing vitamin B12 supplements.

How does pernicious anemia affect my body?

The term “pernicious” means harmful, and pernicious anemia causes harm to several body systems:

  • Digestive system problems that cause nausea, bloating and weight loss.
  • Nervous system damage that causes muscle weakness, numbness or tingling in your hands and feet, memory loss and dementia.
  • Heart problems that can cause palpitations (feeling as your heart is beating too fast or skipping beats).
  • Weakness and fatigue.

Who is affected by pernicious anemia?

Pernicious anemia typically affects people aged 60 to 80 of Northern European descent. Pernicious anemia is estimated to affect 151 in 100,000 people in the United States.


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Symptoms and Causes

What are pernicious anemia symptoms?

Generally speaking, the longer you go without adequate vitamin B12, the more serious your symptoms are. Early on, people may have mild symptoms they may think are caused by other common conditions. Examples include:

What are examples of pernicious anemia symptoms caused by long-term low vitamin B12 levels?

Long-term low vitamin B12 levels caused by pernicious anemia can affect your nervous system. Symptoms of potential nervous system problems include:

  • Confusion.
  • Short-term memory loss.
  • Depression.
  • Loss of balance.
  • Numbness and tingling in your hands and feet.
  • Problems concentrating.
  • Irritability.
  • Hallucinations.
  • Delusions.
  • Optic nerve degeneration that affects your eyesight.

Can I have pernicious anemia without having symptoms?

Yes. Normally, your body stores vitamin B12 that it gets from what you eat. Your body stores vitamin B 12, slowly using it over time. It can take three to five years for your body to use up your vitamin B12 reserves. After that, it can be several more years before you develop pernicious anemia symptoms.

What causes pernicious anemia?

Pernicious anemia is an autoimmune condition that happens when your immune system produces antibodies that attack cells in the mucosal lining of your stomach and nerve cells. Your immune system’s response affects your body’s ability to absorb vitamin B12.

The antibodies also block a critical protein called intrinsic (in-TRIN-sic) factor. Normally, intrinsic factor carries the vitamin B12 we get from food to special cells in your small intestine. From there, the vitamin B12 is transported into your bloodstream. Other proteins then carry the vitamin B12 to your bone marrow, where the vitamin is used to make new red blood cells. This process can’t happen when your immune system blocks your intrinsic factor.

You may also develop vitamin B12 deficiency if:

  • You have surgery to remove part or all of your stomach, which eliminates the cells that enable vitamin B12 absorption. About half of people who have gastric bypass surgery to treat obesity lose cells that enable vitamin B12 absorption.
  • Part or all of your small intestine is surgically removed, reducing your small intestine’s ability to absorb vitamin B12.
  • You have Small Intestine Bacterial Overgrowth (SIBO). SIBO happens when you have too many of the wrong kind of bacteria in your small intestine. This bacteria often uses up any vitamin B12 before your small intestine can absorb the vitamin.
  • You take some medications, including antibiotics for infections and medicines for diabetes and seizures, which affect vitamin B12 levels.
  • You have a tapeworm infection. You can get a tapeworm infection by eating infected fish that was undercooked. Tapeworms feed on vitamin B12.
  • You follow a vegan or vegetarian diet that doesn’t include enough vitamin B12.
  • You have medical conditions that affect your digestive system like celiac disease or Crohn’s disease that make it hard for your body to absorb enough vitamin B12.
  • You have endocrine autoimmune diseases, such as hypoparathyroidism and Graves’ disease, that increase your risk for developing pernicious anemia.


Diagnosis and Tests

How is pernicious anemia diagnosed?

First, your healthcare provider will complete a thorough physical examination and ask questions about your medical history so they know if you’ve any other conditions that may increase your risk of vitamin B12 deficiency. They may ask you if you’re having trouble concentrating. They may look for signs of nervous system problems. Other tests they may do include:

  • Vitamin B12 level.
  • Complete blood count (CBC): This blood test determines the type of anemia you have and the degree of your anemia.
  • Reticulocyte count: This test indicates if your bone marrow can make new red blood cells.
  • Lactate dehydrogenase (LDH) test: LDH is an enzyme that many cells make. Extremely high LDH levels may indicate pernicious anemia.
  • Serum bilirubin levels.
  • Methylmalonic acid (MMA) levels: High MMA levels confirm vitamin B12 deficiency.
  • Homocysteine level: High homocysteine levels may be a sign of vitamin B12 deficiency. Tests for the presence of the antibodies that attack the parietal cells in your stomach and block the action of intrinsic factor.
  • Upper endoscopy: Healthcare providers use a thin, tube-like instrument with a light and lens for viewing called an endoscope to look for signs of degeneration or atrophy (wasting away) of the lining of your stomach.

Management and Treatment

How is pernicious anemia treated?

Since vitamin B12 absorption is blocked, your healthcare provider may prescribe intramuscular vitamin B12 injections. Later, after B12 stores are back to normal, they may prescribe high doses of oral B12 replacement. They’ll monitor your treatment. They may prescribe antibiotics if you have bacteria in your intestine that prevents your body from absorbing vitamin B12.

How soon after treatment will I feel better?

Many people begin feeling better a few days after starting treatment. But you may need a few weeks of regular treatment before you notice significant changes and your condition improves.

Will I always need vitamin B12 treatments or supplements?

Everyone’s situation is different, but most people who have pernicious anemia take vitamin B12 supplements for the rest of their lives.



How can I reduce my risk of developing pernicious anemia?

You can’t prevent pernicious anemia from occurring. But you can reduce your risk by being aware of medical conditions, treatments and activities that may affect your body’s ability to absorb vitamin B12. If you’re concerned about pernicious anemia, ask your healthcare provider if you’re at risk and what steps you can take to avoid vitamin B12 deficiency.

Outlook / Prognosis

What can I expect if I have pernicious anemia?

Most people begin feeling better shortly after starting treatment. Pernicious anemia can’t be cured, but increasing your vitamin B12 intake may eliminate most symptoms. The neurologic complications of pernicious anemia, however, can persist even after B12 stores are fully replaced. If that’s your situation, ask your healthcare provider about other treatments that may ease your symptoms.

Living With

How do I take care of myself?

If you have pernicious anemia, you’ll need to take vitamin B12 supplements regularly for the rest of your life. Other causes of B12 deficiency may be helped by increasing the vitamin B12 in your diet. Some foods to consider adding to your diet include:

  • Breakfast cereals with added vitamin B12.
  • Meats such as beef, liver, poultry and fish.
  • Eggs and dairy products (such as milk, yogurt and cheese).
  • Foods fortified with vitamin B12, such as soy-based beverages and vegetarian burgers.

How often should I see my healthcare provider?

Your healthcare provider may recommend regular appointments so they can monitor your vitamin B12 supplements, your B12 levels and your general health.

What questions should I ask my doctor?

Pernicious anemia symptoms can take years to surface. You may be surprised to learn you have a condition that can cause serious medical problems. Here are some questions you may want to ask your healthcare provider:

  • Why did I develop pernicious anemia?
  • How significant is my vitamin B12 deficiency?
  • Will treatment prevent more serious medical conditions?
  • Are there any side effects to receiving significant amounts of vitamin B12 supplements?
  • Will changing my diet help?
  • I follow a vegan/vegetarian diet. Can I still eat as I choose?

What other vitamin deficiencies can cause anemia?

You can develop vitamin deficiency anemia if your diet doesn’t include enough vitamin B6 or folic acid.

A note from Cleveland Clinic

Pernicious anemia can sneak up on you. You can have this disease for many years before you notice changes in your body that happen because you’re not getting enough vitamin B12. Early pernicious anemia symptoms are mild — so mild that some people simply learn to live with feeling tired, lightheaded or breathless. But diagnosing pernicious anemia early can prevent serious and irreversible problems with your nervous system. You know your body best. If you’re feeling weak and unusually tired, talk to your healthcare provider. If you’re diagnosed with pernicious anemia, they’ll prescribe treatment to restore normal vitamin B12 levels and treat your anemia.

Medically Reviewed

Last reviewed on 02/07/2022.

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