What are symptoms of low folic acid?

November 15, 2025 •

4 min read

According to the Mayo Clinic, folic acid deficiency symptoms can start within weeks, manifesting as extreme tiredness, paleness, and headaches. These signs are a direct result of low folic acid levels disrupting the body's ability to produce healthy red blood cells, which are vital for carrying oxygen.

Quick Summary

A lack of folic acid can lead to megaloblastic anemia, causing symptoms like fatigue, paleness, mouth ulcers, and neurological issues such as confusion and irritability.

Key Points

Fatigue is a top symptom: Persistent, unexplained tiredness and a lack of energy are common indicators of low folic acid due to anemia.
Oral signs are key: A red, sore, or swollen tongue and mouth ulcers can be a distinct sign of a folate deficiency.
Neurological symptoms include brain fog: Difficulty concentrating, irritability, confusion, and memory issues are linked to low folate affecting the nervous system.
Not all deficiencies are the same: Folate and B12 deficiencies share many symptoms, but B12 is more likely to cause permanent nerve damage if misdiagnosed.
Easy to correct with diet and supplements: Increasing intake of folate-rich foods like leafy greens and taking supplements can effectively reverse the deficiency.

Understanding the Role of Folic Acid

Folic acid, or vitamin B9, is a crucial nutrient that plays a vital role in red blood cell formation, cell growth, and DNA synthesis. Since the body only stores a small amount of folate, a diet consistently low in this vitamin can lead to a deficiency within just a few months. When this happens, the body produces abnormally large, immature red blood cells, a condition known as megaloblastic or macrocytic anemia. These oversized cells are inefficient at carrying oxygen, leading to the wide range of symptoms associated with low folic acid.

Common Physical Symptoms

Symptoms of low folic acid often develop gradually and can be subtle at first, becoming more severe as the deficiency progresses. Many of the initial signs are related to anemia and reduced oxygen transport throughout the body.

General Fatigue and Weakness

Extreme Tiredness and Lack of Energy: This is one of the most common and earliest indicators. The body lacks sufficient healthy red blood cells to deliver oxygen efficiently, causing persistent exhaustion that doesn't improve with rest.
Paleness: The reduced number of red blood cells and their associated hemoglobin can lead to noticeably pale skin, particularly on the inner eyelids and nail beds.
Shortness of Breath: Even mild physical exertion, like climbing stairs, can leave an individual breathless as the body struggles to get enough oxygen.
Heart Palpitations: The heart may beat faster or irregularly as it tries to compensate for the reduced oxygen-carrying capacity of the blood.

Oral and Digestive Manifestations

Sore or Red Tongue: The tongue can become smooth, tender, and visibly red, a condition known as glossitis.
Mouth Ulcers: Painful sores or ulcers may develop inside the mouth and on the tongue.
Diarrhea: Some individuals may experience digestive issues, including diarrhea.
Loss of Appetite: This can lead to unexplained weight loss over time.

Neurological and Mental Health Symptoms

Folate is essential for a healthy nervous system, and a deficiency can lead to several mental and neurological issues. While some neurological symptoms overlap with Vitamin B12 deficiency, those caused by folate deficiency are typically reversible with treatment.

Brain Fog and Confusion: Individuals may find it difficult to concentrate, think clearly, or recall memories.
Depression and Irritability: Psychological issues, ranging from mild anxiety and irritability to full-blown depression, can occur.
Memory Problems: Low folate can affect cognitive functions, including memory and judgment.

Other Signs

Premature Hair Graying: A folate deficiency has been anecdotally linked to premature hair graying, although large-scale studies are mixed.
Hair Thinning or Loss: Some research suggests a potential connection between low folate levels and certain types of hair loss, such as alopecia areata, but the evidence is not conclusive.

Folic Acid vs. Vitamin B12 Deficiency: A Comparison

Because Vitamin B12 and folic acid are both crucial for red blood cell production, their deficiencies can present with similar symptoms. However, there are key differences, especially concerning neurological effects. It is vital to distinguish between the two, as treating a B12 deficiency with only folic acid can mask the anemia while allowing neurological damage to progress.


Characteristic	Folic Acid Deficiency	Vitamin B12 Deficiency
Primary Cause	Poor diet, alcoholism, malabsorption issues.	Poor absorption (pernicious anemia), vegan diet.
Symptom Onset	Symptoms can appear within weeks to a few months.	Often a slower onset, over months or years.
Neurological Symptoms	Brain fog, confusion, depression (generally reversible).	Numbness, tingling, balance problems (potentially irreversible nerve damage).
Primary Anemia	Macrocytic/megaloblastic anemia.	Macrocytic/megaloblastic anemia.
Tongue Appearance	Smooth, tender, and red tongue (glossitis).	Sore and red tongue (glossitis).
Diagnosis	Blood test showing low folate levels.	Blood test showing low B12 levels, elevated MMA.

Prevention and Treatment

Preventing a folic acid deficiency involves ensuring an adequate intake of folate-rich foods and, in some cases, taking supplements. The body does not produce folic acid on its own, so it must be acquired through diet.

Foods Rich in Folate

Leafy Green Vegetables: Spinach, kale, and romaine lettuce.
Beans and Legumes: Lentils, chickpeas, and black-eyed peas.
Fortified Grains: Many breads, cereals, and pasta products are enriched with folic acid.
Citrus Fruits: Oranges and grapefruit are good sources.
Liver: Organ meats are a significant source of folate.

If a deficiency is confirmed through a blood test, treatment typically involves taking oral folic acid supplements. In cases of severe deficiency or malabsorption, a doctor may recommend higher doses or other treatments. It is crucial to consult a healthcare provider for a proper diagnosis and treatment plan, especially since many symptoms overlap with other conditions, such as Vitamin B12 deficiency. As noted by Mayo Clinic, many cases of vitamin deficiency anemia can be corrected with supplements.

Conclusion

While a low folic acid level may present subtly at first, its effects can be widespread and impactful, ranging from chronic fatigue and digestive problems to significant neurological and mood changes. Recognizing the key symptoms, especially those related to megaloblastic anemia, is the first step toward diagnosis. Due to the overlap with other conditions like B12 deficiency, a definitive diagnosis requires a blood test conducted by a medical professional. Fortunately, with proper treatment, including dietary adjustments and supplements, the symptoms of low folic acid are often reversible. If you suspect a deficiency, it is important to speak with your doctor to confirm the cause and discuss the right course of action for your health.

Frequently Asked Questions

The fastest way to raise folic acid levels is typically through oral supplements. High doses can correct a deficiency relatively quickly, especially when combined with a diet rich in folate from foods like leafy greens and fortified cereals.

Yes, low folic acid is a very common cause of fatigue. The deficiency leads to a type of anemia where the body produces fewer healthy red blood cells, which are needed to transport oxygen, resulting in extreme tiredness and weakness.

Yes, a severe folic acid deficiency can lead to weight loss. This is often associated with other symptoms like decreased appetite and digestive problems such as diarrhea.

Folate is the naturally occurring form of vitamin B9 found in foods like vegetables and legumes. Folic acid is the synthetic form of vitamin B9, which is often used in supplements and to fortify foods.

Yes, a folic acid deficiency can cause psychological symptoms including depression, anxiety, and confusion. Folate is involved in producing neurotransmitters that regulate mood.

If left untreated, a folic acid deficiency can become serious. It can lead to severe anemia, neurological complications, and, importantly during pregnancy, can increase the risk of birth defects like spina bifida.

Folic acid deficiency is diagnosed with a blood test to measure the concentration of folate in the blood. A healthcare provider will also consider symptoms and medical history.

To increase your folic acid intake, eat foods like green leafy vegetables (spinach, kale), legumes (lentils, chickpeas), fortified breads and cereals, and citrus fruits (oranges).