Which Anemia is Caused by Vitamin B9 Deficiency?

January 11, 2026 •

4 min read

According to the National Institutes of Health, while food fortification has reduced prevalence in many countries, vitamin B9 deficiency can still lead to a serious blood disorder. This condition is known as megaloblastic anemia, which impairs the production of healthy red blood cells.

Quick Summary

A lack of vitamin B9, or folate, leads to megaloblastic anemia, a condition where the body produces abnormally large, immature red blood cells. These dysfunctional cells result in a reduced capacity to transport oxygen, causing symptoms like fatigue and weakness. Treatment typically involves supplementation.

Key Points

Megaloblastic Anemia: This is the specific type of anemia caused by a deficiency of vitamin B9 (folate).
Abnormal Red Blood Cells: A lack of B9 impairs DNA synthesis, leading to the bone marrow producing abnormally large, immature red blood cells called megaloblasts.
Common Symptoms: Signs include fatigue, pale skin, shortness of breath, a sore tongue, and difficulty concentrating.
Multiple Causes: Dietary insufficiency is a major cause, but malabsorption issues, increased bodily demand (like during pregnancy), and certain medications can also trigger the deficiency.
Effective Treatment: The condition is treated with folic acid supplements and by increasing the intake of folate-rich foods.
B12 Check is Crucial: Before initiating folate treatment, a vitamin B12 deficiency must be ruled out, as treating only the folate deficiency can mask a serious underlying B12 issue.

Understanding Anemia and Folate

Anemia is a condition characterized by a shortage of healthy red blood cells, which are responsible for carrying oxygen throughout the body. There are many different types of anemia, each with its own specific cause. Vitamin B9, also known as folate, plays a crucial role in the production of red blood cells. When there is a deficiency of this vitamin, it disrupts the normal cell division process in the bone marrow. The result is a specific type of anemia known as megaloblastic anemia.

What is Megaloblastic Anemia?

Megaloblastic anemia is a form of macrocytic anemia, which means the red blood cells produced are larger than normal. The term 'megaloblast' refers to these abnormally large, immature red blood cells found in the bone marrow. Due to their size and underdevelopment, these cells are often unable to leave the bone marrow and enter the bloodstream effectively. Those that do are frequently destroyed prematurely, leading to a reduced overall red blood cell count and insufficient oxygen delivery to the body's tissues.

Symptoms of Vitamin B9 Deficiency Anemia

The symptoms of megaloblastic anemia often develop gradually and can be subtle at first. As the condition worsens, they become more pronounced.

Fatigue and Weakness: A lack of oxygen delivery to the muscles and organs can cause persistent tiredness and overall weakness.
Pale Skin: Insufficient red blood cells can result in a noticeable paleness of the skin, known as pallor.
Shortness of Breath: Reduced oxygen-carrying capacity can cause breathlessness, especially during physical exertion.
Oral Symptoms: A smooth, red, and swollen tongue (glossitis) is a common sign, along with mouth sores.
Cognitive and Mood Changes: Irritability, difficulty concentrating, and memory issues can occur.
Digestive Issues: Symptoms may include decreased appetite, weight loss, and diarrhea.

Causes of Folate Deficiency

There are several reasons why a person might not have enough folate to produce healthy red blood cells.

Poor Diet: Not eating enough folate-rich foods is a primary cause. Folate is a water-soluble vitamin and is not stored in the body for long periods, making a consistent intake necessary.
Malabsorption: Certain conditions affecting the digestive tract, such as celiac disease or Crohn's disease, can prevent the proper absorption of folate from food.
Increased Requirement: The body's need for folate increases during periods of rapid cell division, such as pregnancy and infancy. Chronic conditions like hemolytic anemia and certain cancers also increase folate demand.
Excessive Alcohol Consumption: Alcohol interferes with folate absorption and metabolism, increasing the risk of deficiency.
Medications: Some drugs, including certain anti-seizure medications, can interfere with the body's ability to absorb or use folate.

Diagnosis and Treatment of Megaloblastic Anemia

Accurate diagnosis is crucial because vitamin B12 deficiency can also cause megaloblastic anemia and may have neurological complications if not treated correctly. A healthcare provider will perform a physical exam and review medical history before ordering tests.

Comparison of Anemia Types


Feature	Megaloblastic Anemia	Iron-Deficiency Anemia	Aplastic Anemia
Primary Cause	Deficiency of Vitamin B9 (folate) or B12	Lack of iron	Bone marrow damage
Red Blood Cell Size	Abnormally large (Macrocytic)	Abnormally small (Microcytic)	Normal size (Normocytic)
RBC Appearance	Oval-shaped, immature megaloblasts	Pale, smaller cells	Normal appearance
Symptoms	Fatigue, pale skin, sore tongue, mood changes	Fatigue, pale skin, brittle nails, restless leg syndrome	Fatigue, frequent infections, easy bruising
Common Treatment	Oral supplements or injections of the deficient vitamin	Iron supplements and dietary changes	Immunosuppressants, stem cell transplant

Treatment Options

Folic Acid Supplements: The main treatment for folate deficiency is taking oral folic acid tablets daily. In cases of severe malabsorption, injections may be necessary. Treatment typically lasts for several months until normal folate levels are restored and blood parameters normalize.
Dietary Changes: Patients are advised to increase their intake of folate-rich foods, including green leafy vegetables, citrus fruits, and fortified cereals.
Address Underlying Cause: If the deficiency is caused by a medical condition or medication, the underlying issue must be addressed to prevent recurrence.
B12 Check: Before starting folate supplementation, it is essential to rule out a concurrent vitamin B12 deficiency. Administering folate to a person with an underlying B12 deficiency can mask the anemia symptoms while allowing neurological damage to progress.

Conclusion

Vitamin B9 deficiency causes megaloblastic anemia, a condition stemming from impaired DNA synthesis that leads to the production of oversized, immature red blood cells. Symptoms like fatigue, pallor, and a sore tongue can indicate the issue, while risk factors include poor diet, certain medical conditions, and excessive alcohol use. Timely diagnosis, which includes distinguishing it from other anemias, allows for effective treatment, primarily involving folic acid supplements and dietary adjustments. Correcting the deficiency is key to restoring healthy red blood cell production and alleviating symptoms.

Authoritative Source

Cleveland Clinic Journal of Medicine: Severe Megaloblastic Anemia

Frequently Asked Questions

The primary anemia caused by a lack of vitamin B9 (folate) is megaloblastic anemia. This condition results in the production of abnormally large, immature red blood cells.

Yes, a deficiency in vitamin B12 can also cause megaloblastic anemia. This is why it is essential to determine which vitamin is lacking before beginning treatment.

Common symptoms include extreme fatigue, paleness of the skin (pallor), a sore and swollen tongue (glossitis), diarrhea, irritability, and shortness of breath.

Folate deficiency is typically diagnosed through a physical exam and blood tests. A complete blood count (CBC) and specific serum folate level testing can confirm the diagnosis.

Treatment involves taking daily folic acid supplements, often for several months. Dietary changes to include more folate-rich foods are also recommended.

Foods rich in folate include leafy green vegetables (like spinach), citrus fruits, legumes, fortified cereals and grains, and beef liver.

Checking for B12 deficiency is vital because treating a B12-deficient patient with only folic acid can improve the anemia but allow underlying neurological damage to progress without being addressed.