What Happens When Folic Acid is Low in the Body?

November 17, 2025 •

3 min read

According to the National Institutes of Health, a deficiency in folate can occur within just a few weeks if dietary intake is inadequate. A low level of folic acid, the synthetic form of this essential B vitamin, can have significant repercussions throughout the body, affecting everything from energy levels to cellular health.

Quick Summary

A lack of folic acid in the body impairs red blood cell production, leading to megaloblastic anemia, fatigue, and weakness. It can also cause oral issues, neurological symptoms, and, most critically, serious birth defects during pregnancy. Proper diagnosis involves blood tests and treatment includes supplements and dietary changes.

Key Points

Megaloblastic Anemia: Low folic acid causes abnormally large, immature red blood cells, leading to fatigue and weakness.
Pregnancy Complications: A deficiency during early pregnancy significantly increases the risk of neural tube defects like spina bifida and anencephaly.
Neurological Symptoms: Low folate is linked to mood disorders, including depression, and can cause cognitive issues like confusion and memory problems.
Oral Health Issues: Symptoms can include a sore, red tongue (glossitis), mouth ulcers, and a reduced sense of taste.
Risk Factors: Causes range from poor diet and alcohol use to malabsorption disorders (like celiac disease) and certain medications.
Diagnosis and Treatment: A blood test can diagnose the deficiency, which is typically treated with folic acid supplements and a folate-rich diet.

Folic acid, also known as vitamin B9, is crucial for creating and maintaining new cells, including red blood cells. Since the body doesn't store it long-term, a consistent intake is necessary. Understanding what happens when folic acid is low in the body reveals a range of health problems stemming from impaired cell synthesis.

Consequences of Low Folic Acid

Impact on Red Blood Cells: Megaloblastic Anemia

A primary consequence of low folic acid is megaloblastic anemia. This condition is characterized by the production of large, immature, and fewer red blood cells. These abnormal cells are less effective at carrying oxygen, leading to symptoms such as:

Fatigue and weakness
Pale skin
Shortness of breath
Irritability
Dizziness

Oral and Digestive Issues

Low folic acid can also manifest as problems in the mouth and digestive tract. Symptoms can include a sore, red, and swollen tongue (glossitis), mouth ulcers, and a diminished sense of taste. Some individuals may also experience diarrhea and weight loss.

Neurological and Mental Health Effects

Folate deficiency can impact brain function and mental well-being. Studies suggest a link between low folate levels and mood disorders, with a higher prevalence in individuals with depression. Other potential neurological and psychological symptoms include:

Poor memory and concentration
Confusion
Changes in behavior
Potential for cognitive decline in severe, long-term cases

Risks During Pregnancy

For pregnant individuals, adequate folic acid is vital, especially in early pregnancy, for the proper development of the baby's neural tube, which forms the brain and spinal cord. A deficiency significantly increases the risk of neural tube defects (NTDs) like spina bifida and anencephaly. These can cause severe disabilities or be fatal.

Causes of Folic Acid Deficiency

Low folic acid levels can result from various factors:

Insufficient dietary intake of folate-rich foods.
Conditions affecting nutrient absorption, such as celiac or Crohn's disease.
Chronic heavy alcohol consumption.
Certain medications, including some for seizures and cancer.
Increased bodily needs, like during pregnancy and breastfeeding.
Genetic factors impacting folate metabolism.

Diagnosis and Treatment

Diagnosis typically involves a blood test to measure serum folate levels. Vitamin B12 levels may also be checked. Treatment usually involves:

Taking folic acid supplements, often for several months.
Increasing dietary intake of folate-rich foods.

Comparison: Folate vs. Folic Acid


Feature	Folate (Natural)	Folic Acid (Synthetic)
Source	Found in foods like leafy greens, legumes.	Used in supplements and fortified foods.
Absorption	Processed in small intestine, variable bioavailability.	More stable and easily absorbed.
Metabolism	Metabolized directly in small intestine.	Metabolized in the liver, requires an extra step.
Stability	Unstable, easily destroyed by heat/light.	Very stable, good for fortification/supplements.
Recommended Use	General dietary intake.	Crucial for pregnant/planning-to-conceive individuals due to stability/absorption.

Conclusion

Low folic acid in the body leads to a variety of health issues, notably affecting red blood cell production, neurological function, and fetal development. Symptoms, though sometimes general, can be diagnosed with a blood test. Treatment with supplements and dietary changes is usually effective. Early detection and management are vital, especially for at-risk groups like pregnant women, to prevent serious complications.

Authoritative Resource

For more details on folate, consult the Office of Dietary Supplements at the National Institutes of Health.

Frequently Asked Questions

Folic acid, or vitamin B9, is essential for producing and maintaining new cells, including red blood cells. It plays a crucial role in the synthesis and repair of DNA and RNA.

Early signs can be subtle and include general fatigue, weakness, a lack of energy, and irritability. As the deficiency worsens, symptoms become more pronounced.

A lack of folic acid early in pregnancy can lead to severe birth defects known as neural tube defects, such as spina bifida and anencephaly, which affect the baby's brain and spinal cord.

Folate is the naturally occurring form of vitamin B9 found in food, while folic acid is the synthetic form used in supplements and fortified foods. Folic acid is more stable and better absorbed by the body.

Foods rich in folate include dark leafy green vegetables (like spinach and kale), legumes (beans and lentils), citrus fruits, eggs, and fortified grain products.

Yes, low folic acid levels can affect brain function. It has been linked to mood disorders, poor memory, difficulty concentrating, and, in severe cases, cognitive decline.

A doctor can diagnose folic acid deficiency with a simple blood test that measures the levels of folate in the blood. They may also check vitamin B12 levels, as these deficiencies often coexist.

Individuals at a higher risk include pregnant women, those with poor dietary intake, people with malabsorption conditions (like celiac disease), chronic alcohol users, and individuals on certain medications.