Folate deficiency symptoms can include tongue inflammation, mouth sores, and fatigue.
You may be at a greater risk of folate deficiency if you are pregnant, or have Chrohn's disease or celiac disease.
To get more folate, you should eat more leafy greens in your diet and consider taking a folic acid supplement.
This article was medically reviewed by Samantha Cassetty, MS, RD, nutrition and wellness expert with a private practice based in New York City.
Visit Insider's Health Reference library for more advice.

Folate, also called B9, is an essential B vitamin that our bodies use to form DNA and produce red blood cells. A folate deficiency can cause symptoms like weakness and headaches to depression and decreased nerve functioning.

Here's everything you need to know about folate deficiency, from recognizing the signs and symptoms to finding the right treatment plan.
What does folate do?

Folate helps with a series of tasks across the body.

According to Elizabeth Klingbeil, PhD, RDN, LDN, an assistant professor in the department of nutrition & dietetics at Johnson & Wales University, folate's functions include:

Formation of DNA
Breaking down protein so it can be utilized by the body
Brain functioning and development
Red blood cell production
Promoting proper fetal development

Signs and symptoms of folate deficiency

Understanding the symptoms of a folate deficiency can help you and reach out to a doctor for diagnosis and treatment. While symptoms may change over time as folate levels fluctuate, according to Klingbeil and Rebecca Guterman, a dietitian in New York City, mild symptoms of folate deficiency include:

Tongue inflammation
Mouth sores
Fatigue
Weakness
Irritability
Headache

According to Klingbeil, if a folate deficiency is left untreated, more severe symptoms can develop over time, including:

Depression
Decreased nerve function
Developmental issues for a fetus if you are pregnant

Causes of folate deficiency

Folate deficiency occurs when folic acid blood levels drop below 2 ng/mL in blood plasma and 140 ng/mL in red blood cells. There are many factors that can cause folate deficiency, but it usually occurs when you do not consume enough folate in your diet.

Your recommended daily intake of folate depends on your age and other factors:

Age Male Female Pregnancy Lactation
Birth to 6 months 65 mcg 65 mcg
7–12 months 80 mcg 80 mcg
1–3 years 150 mcg 150 mcg
4–8 years 200 mcg 200 mcg
9–13 years 300 mcg 300 mcg
14–18 years 400 mcg 400 mcg 600 mcg 500 mcg
19+ years 400 mcg 400 mcg 600 mcg 500 mcg

Some people are at increased risk of developing a folate deficiency. This includes women who are pregnant, as the fetus requires large amounts of folate to develop properly. That's why women who are trying to get pregnant should consider taking a folate-containing prenatal vitamin to prevent a deficiency that could harm their baby.

"Inadequate folate during pregnancy, especially during the first 28 days of development, is related to neural tube defects — such as spina bifida or other neurological issues — in the developing fetus," says Klingbeil.

According to Guterman, other conditions that increase your risk of folate deficiency include:

Alcoholism
Malnutrition
Celiac disease
Crohn's disease

Diagnosis

If you suspect you have a folate deficiency, it's important to visit your doctor so they can confirm symptoms are not due to another deficiency or underlying health problems. Additionally, Klingbeil strongly recommends speaking to your doctor if you're experiencing:

Ongoing depression
Mental confusion
Fatigue
Diarrhea
Nerve problems

Your doctor will order a blood test to confirm the deficiency. "Folate deficiency will most commonly present itself as megaloblastic anemia," says Klingbeil. A person with megaloblastic anemia will produce structurally large, irregular, and immature red blood cells, also known as megaloblasts. Through a blood test, your doctor can determine if your red blood cells are megaloblasts or normal.
Treatment

Folate deficiency is often treated through dietary changes that increase the amount of folate-rich foods you consume. Foods high in folate include:

Broccoli
Chickpeas
Brussel sprouts
Leafy greens, such as cabbage and spinach
Peas
Whole grains
Eggs

Supplements

Changes to your diet are generally the first step in remedying a folate deficiency. However, people who can not consume enough folate from food alone due to dietary restrictions or absorption issues may use supplements. Supplements contain folic acid — the man-made version of folate which is more easily absorbed by the body.

"I advise individuals to not take a supplement that is over 100% of the recommended dietary allowance of folate to avoid vitamin toxicity," says Klingbeil. The upper limit intake of folate is 1,000 mcg a day for adults. A medical professional can help you determine if you need a supplement, and what dosage you should be taking.
Insider's takeaway

Folate is a vitamin used for DNA formation, fetal development, and red blood cell production. Folate deficiency occurs when you consume less than your daily recommended intake of 400 mcg, and causes symptoms like headaches, weakness, and mouth sores. It can be treated by increasing your intake of folate-rich foods or taking a supplement.