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Sep 08, 2021
5 min read

Pernicious anemia: what is it, symptoms, diagnosis, treatment

Pernicious anemia occurs when a lack of vitamin B12 causes low red blood cell and hemoglobin levels in the blood. It’s a rare disease often caused by an autoimmune condition that lowers the amount of intrinsic factor, a protein needed to absorb vitamin B12. Treatment involves supplementation of vitamin B12 and regular monitoring with your healthcare practitioner.

felix gussonemolly knudsen

Reviewed by Felix Gussone, MD

Written by Molly Knudsen, MS, RDN

Disclaimer

If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

Pernicious anemia is one form of anemia—a condition that arises due to low levels of red blood cells or a protein called hemoglobin in the blood. 

It is a rare condition that affects around 0.1% of people or 1.9% of people over 60 years of age (Rodriguez, 2021). Pernicious means harmful, damaging, or destructive. And that’s the term that was used to define this type of anemia before treatments were made available. However, it can now be fully diagnosed, treated, and managed. 

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What is pernicious anemia?

Pernicious anemia occurs when the body doesn’t have enough vitamin B12 to support healthy red blood cell production. 

Vitamin B12 is involved in making red blood cells, and when there’s not enough of this essential nutrient, red blood cells are too large. Red blood cells are produced in bone marrow, and if they’re too large, they may not be able to leave the bone marrow and enter the bloodstream. This leads to pernicious anemia, a type of megaloblastic anemia (AKA when blood cells are large or have structural abnormalities) (Rodriguez, 2021). 

Symptoms of pernicious anemia 

A person experiencing this type of anemia may show signs of both anemia and vitamin B12 deficiency, including (Rodriguez, 2021; Langan, 2017): 

  • Fatigue 
  • An unhealthy paleness
  • Chest pain 
  • Headaches
  • Tingling/numbness in hands and feet
  • Weakness
  • Confusion
  • A smooth, thick, red tongue

What causes it?

There are several common causes of pernicious anemia, including lack of intrinsic factor, malabsorption, and a low dietary intake of vitamin B12.

Lack of intrinsic factor

Intrinsic factor is the name of a protein made in the stomach. It specifically helps the body absorb vitamin B12. But, absorption of vitamin B12 occurs in the intestines because the stomach is too acidic for intrinsic factors to bind to vitamin B12 there (Rodriguez, 2021). 

In some cases, the body produces antibodies that target the cells in the stomach responsible for making intrinsic factors. This is a type of autoimmune condition. So the body doesn’t make enough intrinsic factor, and vitamin B12 can’t be absorbed (Rodriguez, 2021). 

Malabsorption

There are other reasons the body may not be able to absorb vitamin B12 in addition to lack of intrinsic factor, including (Rodriguez, 2021):

  • Celiac disease, Crohn’s disease, or chronic pancreatitis 
  • Surgeries on the stomach or intestines (gastrectomy or small bowel resection)
  • Some antibiotics, diabetes, or anti-seizure medications
  • A tapeworm infection 
  • Overgrowth of harmful bacteria in the small intestine 

Low dietary intake of vitamin B12 

Animal protein foods like meat, poultry, fish, eggs, and dairy products are rich sources of vitamin B12. Vegetarians and especially strict vegans (people who consume no animal products) may not be getting enough vitamin B12 in the diet (Pawlak, 2013). 

Vegetarians and vegans should consider talking with a healthcare professional to see if supplementing with vitamin B12 may be necessary to meet their nutrient needs. 

Risk factors

Since vegetarians and vegans are more likely to lack vitamin B12 in their diets, they are at risk for deficiency and pernicious anemia. In addition, it is a global problem and affecting people from Northern Europe, South America, Africa, and Asia (Green, 2017). 

Other risk factors for developing pernicious anemia include (Rodriguez, 2021):

  • Genetic predisposition (AKA family history)
  • Surgical removal or alterations to the stomach or small intestine
  • Medications that interfere with vitamin B12 absorption 

How do you prevent it?

Pernicious anemia that arises from not getting enough vitamin B12 in the diet can be prevented by ensuring adequate intake. Whether that’s by eating vitamin B12-rich foods like animal proteins, vitamin B12 fortified foods like cereals and bread, or by supplementation (Langan, 2017). 

If it stems from a lack of intrinsic factor, prevention lies in proper screening at your doctor’s office. 

Diagnosis

To diagnose pernicious anemia, doctors will take a medical and family history and conduct a physical exam. This allows them to determine if you may be at a greater risk of pernicious anemia and if you are exhibiting signs or symptoms (like pallor). However, several blood tests are also needed to confirm a diagnosis, including (Rodriguez, 2021; Rojas Hernandez, 2015):

  • Complete blood count
    • Hemoglobin: A protein found in red blood cells that helps carry oxygen. This value will likely be low in people with pernicious anemia.
    • Hematocrit: The proportion of red blood cells in the blood. This value will likely be low.
    • Platelets: Cells that help blood clot. This value may be abnormal in people with pernicious anemia. 
    • Mean corpuscular volume (MCV): A measure of the average size of red blood cells. This value will likely be larger than average. 
  • Serum vitamin B12
    • Low levels of vitamin B12 in the blood may indicate pernicious anemia. 
  • Folic acid levels
    • Low levels of folic acid can also lead to low vitamin B12 levels.
  • Intrinsic factor and parietal cell antibodies
  • The presence of these antibodies indicates pernicious anemia. 
  • Homocysteine
    • An amino acid found in the blood. Vitamin B12 breaks homocysteine down to make other compounds the body needs. Homocysteine levels will appear high in people with pernicious anemia. 

Treatments

Treating pernicious anemia involves correcting low levels of vitamin B12. This can be done through vitamin B12 injections or supplements. 

Shots given in the muscle are a more immediate way to increase vitamin B12 and can be given daily, weekly, or monthly, depending on the need. Your doctor will monitor vitamin B12 levels in the blood throughout this process. Vitamin B12 supplements are available as pills or as a nasal spray (Rojas Hernandez, 2015). 

If an underlying condition impacts your ability to absorb vitamin B12, your doctor may prescribe you a medication to specifically treat that. Or, if a medication is the cause, your healthcare provider may swap out the medication for something new or change the dose (Rodriguez, 2021). 

The outlook of living with pernicious anemia

While they may need vitamin B12 treatments for life, those living with pernicious anemia can live healthy lives with the proper treatment. Follow-up visits with a healthcare provider are necessary to monitor the condition and to watch out for any complications. Complications may include nerve damage, clots, tongue inflammation, or stomach cancer (Rodriguez, 2021).

Talk to your healthcare practitioner if you think you may have this type of anemia, as early diagnosis and prompt treatment is essential. 

References

  1. Green, R., Allen, L. H., Bjørke-Monsen, A. L., Brito, A., Guéant, J. L., Miller, J. W., et al. (2017). Vitamin B12 deficiency. Nature Reviews: Disease Primers, 3, 17040. doi: 10.1038/nrdp.2017.40. Retrieved from https://pubmed.ncbi.nlm.nih.gov/28660890/.
  2. Langan, R. C., & Goodbred, A. J. (2017). Vitamin B12 Deficiency: Recognition and Management. American Family Physician, 96(6), 384–389. Retrieved from https://pubmed.ncbi.nlm.nih.gov/28925645/
  3. Pawlak, R., Parrott, S. J., Raj, S., Cullum-Dugan, D., & Lucus, D. (2013). How prevalent is vitamin B(12) deficiency among vegetarians?. Nutrition Reviews, 71(2), 110–117. doi.org/10.1111/nure.12001. Retrieved from https://pubmed.ncbi.nlm.nih.gov/23356638/
  4. Rodriguez, N. M, Shackelford, K. Pernicious Anemia. [Updated Jul 7, 2021]. In: StatPearls [Internet]. Retrieved from: https://www.ncbi.nlm.nih.gov/books/NBK540989/
  5. Rojas Hernandez, C. M., & Oo, T. H. (2015). Advances in mechanisms, diagnosis, and treatment of pernicious anemia. Discovery Medicine, 19(104), 159–168. Retrieved from https://pubmed.ncbi.nlm.nih.gov/25828519/