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Understanding Megaloblastic Anemia – Causes, Symptoms, and Treatment

What is Megaloblastic Anemia?

Megaloblastic anemia is a condition in which there are unusually large red blood cells. The bone marrow may make fewer of them and also, they do not mature and function properly.

Megaloblastic Anemia - Causes, Symptoms, and Treatment

Red blood cells play the role of carrying oxygen to the tissues and organs of the body. Any type of abnormality in the red blood cells interferes with oxygen delivery.

Megaloblastic anemia is not a rare condition but the cause of its prevalence is not known due to limited research. A study done on 1150 people found that megaloblastic anemia occurred in 3.6% of them.(1)

Causes of Megaloblastic Anemia

Megaloblastic anemia occurs commonly due to the deficiency of vitamin B12 or vitamin B6. Both of these vitamins are involved in the development of healthy red blood cells. A lack of these vitamins may affect the development of red blood cells.

Sometimes there is an inherited condition that may affect the absorption of these vitamins and lead to megaloblastic anemia. Some infants have a congenital error of folate metabolism.

Causes of Vitamin B12 Deficiency

Vitamin B12 deficiency is a major cause of megaloblastic anemia and it can occur due to the following reasons:(2)

  • Autoimmune Condition: A person’s ability to absorb vitamin B12 is affected due to pernicious anemia.
  • Digestive Condition: The nutrients from the food are absorbed in the small intestine. Celiac disease is a condition that damages the small intestine and leads to vitamin B12 deficiency.
  • Diet: Liver stores excess vitamin B12. Those eating fewer vitamin B12 foods have a risk of developing a deficiency.

Risk Factors for Megaloblastic Anemia

There are a few factors that increase a person’s risk of developing megaloblastic anemia. These are mostly those conditions affecting vitamin B12 absorption.

  • Diet: A diet low in vitamin B12 increases the risk of vitamin B12 deficiency. A study reported an 80% prevalence of vitamin B12 deficiency in India and Hong Kong as more people here eat and are vegan and do not consume B12-fortified foods.(3)
  • Medication: Certain medications including metformin and proton pump inhibitors limit the absorption of vitamin B12.
  • Medical conditions: Certain medical conditions including ulcerative colitis and Crohn’s disease may interfere with the absorption of vitamin B12.(4)

Symptoms of Megaloblastic Anemia

The symptoms of megaloblastic anemia develop slowly and sometimes a person may not have symptoms for years. Lack of red blood cells affects the amount of oxygenated blood that travels to various parts of the body and leads to the following symptoms:

Diagnosis of Megaloblastic Anemia

To diagnose megaloblastic anemia the doctors take the medical history that helps in establishing the risk factor. A physical exam is done to rule out other conditions. Blood tests are ordered including:

  • Complete Blood Count: To get information about the red blood cells, white blood cells, and platelet.
  • Peripheral Blood Smear: To look at the shape and size of the red blood cells.
  • Reticulocyte Count: To check immature red blood cells in bone marrow

A blood test can be helpful in diagnosing megaloblastic anemia.

Treatment of Megaloblastic Anemia

Treatment of megaloblastic anemia is usually focused on addressing the underlying cause of the condition. In most cases, the primary cause of megaloblastic anemia is a deficiency in vitamin B12 or folate, and the main treatment is to supplement the patient with these vitamins. The specific treatment plan for an individual will depend on their specific circumstances and the underlying cause of their megaloblastic anemia.

For patients with vitamin B12 deficiency, treatment usually involves taking vitamin B12 supplements in the form of injections, oral tablets, or nasal sprays. The recommended dose of vitamin B12 will depend on the severity of the deficiency and the individual’s age and medical history. Vitamin B12 supplements can be taken long-term, and some patients may require lifetime treatment to maintain adequate levels of the vitamin.

For patients with folate deficiency, treatment typically involves taking folate supplements in the form of oral tablets. The recommended dose of folate will depend on the severity of the deficiency and the individual’s age and medical history. Like vitamin B12, folate supplements can be taken long-term, and some patients may require lifetime treatment to maintain adequate levels of the vitamin.

In some cases, megaloblastic anemia may be caused by a medical condition or medication that interferes with the absorption of vitamin B12 or folate. In these cases, the primary treatment will be to address the underlying medical condition or medication. This may involve changing medications or treating the underlying medical condition.

Overall, treatment for megaloblastic anemia is highly effective in addressing the underlying deficiency and restoring healthy red blood cell function. Patients who receive appropriate treatment typically experience improvement in their symptoms and a return to normal red blood cell function. It is important to work closely with a healthcare professional to develop a treatment plan that is tailored to the individual’s specific needs.

How to Prevent Megaloblastic Anemia

The best way to prevent megaloblastic anemia is to eat food rich in vitamin B12. If due to some reason, a person is not able to make it up in the diet, supplements are available.

Foods rich in vitamin B12 include:

  • Chicken
  • Tuna
  • Salmon
  • Milk
  • Beef
  • Eggs

If someone observes having pale skin, shortness of breath, and fatigue, it is good to consult a doctor. With proper treatment megaloblastic anemia has a good outlook.(5) The most frequent cause of this condition is decreased intake of vitamin B12 in the diet. Most of the cases get help with supplement intake. With proper and timely treatment this condition is usually not fatal.


  1. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). (2021). Vitamin B12 Deficiency Anemia. https://www.niddk.nih.gov/health-information/digestive-diseases/vitamin-b12-deficiency-anemia
  2. Mayo Clinic. (2021). Megaloblastic anemia. https://www.mayoclinic.org/diseases-conditions/megaloblastic-anemia/diagnosis-treatment/drc-20352388
  3. American Society of Hematology. (2021). Vitamin B12 and Folate Deficiencies. https://www.hematology.org/education/patients/anemia/vitamin-b12-and-folate
  4. U.S. National Library of Medicine. (2021). Megaloblastic anemia. https://medlineplus.gov/ency/article/000563.htm
  5. World Health Organization (WHO). (2021). Vitamin B12 and Folate Deficiencies. https://www.who.int/nutrition/topics/vitaminb12_folate_deficiencies/en/
Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:February 3, 2023

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