What Is Pernicious Anemia?

Medically Reviewed by Carol DerSarkissian, MD on May 10, 2021

When your body can’t make enough healthy red blood cells because it lacks vitamin B-12, you have pernicious anemia (PA). A long time ago, this disorder was believed to be fatal (“pernicious” means deadly). These days it’s easily treated with B-12 pills or shots. With treatment, you’ll be able to live without symptoms.

Your body needs plenty of healthy red blood cells. These are what carry oxygen to every part of your body. Without them, your tissues and organs don’t work like they should.

Vitamin B-12 is a crucial part of this process. If your body doesn’t absorb enough from the food you eat, your red blood cells will be too big to travel well through your body. Because of this, your body will make less of them. And the cells that are made will die off sooner than they should.

The reason this happens is often due to the lack of a stomach protein called “intrinsic factor” (IF). Your body can’t absorb vitamin B-12 without it.

Some health issues make you more likely to have PA. These include:

Some medicines, like antacids or drugs that treat type 2 diabetes, can make it harder for your body to absorb enough B-12.

A strict vegetarian diet puts you at risk for PA too, since you won’t be eating foods that are rich in B-12 like eggs, milk, and poultry.

Also, if someone else in your family has PA, your risk of having it goes up as well.

PA affects people in different ways. These can be signs you have it:

  • Fatigue (Many people wake up tired despite getting enough sleep.)
  • Shortness of breath
  • Feeling dizzy
  • Cold hands and feet
  • Chest pain
  • Pale or yellow skin
  • Trouble with balance (for example, struggling to put on your pants or socks while you’re standing)
  • A burning feeling in your legs or feet. This may get worse at night
  • Depression
  • Trouble focusing

Your doctor will ask about your family history. They’ll want to know your symptoms, plus what types of food you often eat and any medicines you take every day.

During a physical exam, your doctor will listen to your heart, check to see if your liver’s enlarged, and look for any signs of nerve damage. They may do tests that check your balance, how well you can walk, and your mental status.

Your doctor will also order blood work. This can reveal if you have a low amount of hemoglobin. That’s the substance in red blood cells that helps carry oxygen throughout your body. It can check to see the size and shape of your red blood cells. It can also tell the amount of B-12 in your blood that’s “active,” and ready for your body to use.

Vitamins you buy at the drug store don’t have enough B-12 in them to treat PA. Your doctor will need to prescribe a special supplement to you. This is often given in a shot. At first, you may need to have one every other day. Over time, you may be able to cut back to once a month.

Extra B-12 can also be prescribed as a pill, nose spray, nasal gel, or medicine you put under your tongue.

Your doctor will likely also suggest some changes to your diet. Eating more foods that are high in vitamin B-12 can help you feel better, too.

Show Sources


National Heart, Lung and Blood Institute: “What Is Pernicious Anemia?”

Pernicious Anaemia Society: “Patients FAQ,” “What are the signs and symptoms?”

Johns Hopkins Medicine: “Vitamin B12 Deficiency Anemia.”

National Health Service (U.K.): “Vitamin B12 or folate deficiency anaemia – Diagnosis.”

Mayo Clinic: “Vitamin Deficiency Anemia.”

FamilyDoctor.org: “Vitamin B-12.”

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