Pronunciation: foe-lick as-id
Generic name: folic acid
Brand names: FA-8, Folacin-800, FaLessa, Folvite
Dosage form: oral tablet (0.4 mg; 0.8 mg; 1 mg), injection
Drug class: Vitamins

Medically reviewed by Carmen Pope, BPharm. Last updated on Jul 10, 2024.

What is folic acid?

Folic acid (vitamin B9) is a B vitamin supplement that may be used to prevent and treat folate deficiency (low blood levels of folate) that can cause megaloblastic anemia. Folic acid may also be used to control high levels of homocysteine, prevent serious birth defects in pregnant women or women who think they may be pregnant, and prevent methotrexate-induced folate deficiency in people prescribed methotrexate.

Folic acid has been FDA approved since 1947.

Folate vs folic acid

Folate is the natural form of vitamin B9 found in various foods. Folic acid is the man-made form of vitamin B9 created in a laboratory that is added to fortified foods or used as a supplement. Folic acid is more stable and easier to absorb than naturally occurring folate in food. When you take folic acid, your body turns it into folate. 

Folic acid benefits

Vitamin B9 (folate, folic acid) plays a crucial role in healthy red blood cell production and is also vital for cell growth, repair, and DNA synthesis.

• Red blood cells carry oxygen throughout your body, and folate deficiency can lead to a type of anemia called folate-deficiency anemia. Symptoms of this anemia include fatigue, weakness, shortness of breath, and pale skin.
• Folate is especially important during periods of rapid cell division, such as pregnancy and fetal development.

Benefits of folic acid supplementation include:

Preventing and treating folate-deficiency anemia. Folate is vital for the production of red blood cells (RBCs)  and low levels of folate can cause folate-deficiency anemia (known medically as megaloblastic anemia), characterized by RBCs that are unusually large, structurally abnormal, and do not function properly. There are also fewer of them. 

Preventing neural tube and other birth defects in the developing fetus in pregnant women. Folic acid helps ensure the proper closure of the neural tube early in pregnancy. The neural tube forms the brain, spinal cord, and surrounding structures and closes 28 to 32 days after a baby is conceived, which is often before many women know they are pregnant. This is why the CDC recommends all people capable of becoming pregnant get 400 micrograms (mcg) of folic acid daily.

• This means women should start taking folic acid BEFORE they are pregnant, at the time they decide to try for a baby.

Lowering high levels of homocysteine in the blood (hyperhomocysteinemia). This can be caused by low dietary intake of folic acid, folate, vitamin B6, vitamin B12, thyroid disease, kidney disease, psoriasis, genetic reasons, or some medications. High homocysteine levels can damage the lining of the arteries and make blood clot more easily which can increase your risk of cardiovascular disease.

Reducing toxicity caused by the drug methotrexate. Methotrexate can cause low levels of folate in the body which can increase the risk of side effects such as nausea, vomiting, and mouth sores. Taking folic acid 5mg weekly, on a different day to the methotrexate dose seems to reduce these side effects.

Potential Other Benefits. Research is ongoing, but folic acid may have other benefits, such as reducing the risk of certain cancers, supporting mood and cognitive function, and possibly reducing the risk of dementia and the development of autism spectrum disorder (ASD).

What are the symptoms of folate deficiency?

Folate deficiency can be caused by not enough folate in the diet, a problem absorbing folate, or an increased need for folate (for example pregnant or breastfeeding women). Folate deficiency symptoms include:

• fatigue, feeling tired, or rundown
• heart palpitations or a fast heartbeat
• shortness of breath
• mouth ulcers, or an inflamed and painful tongue
• mood changes, such as depression or irritability
• sleep problems, such as insomnia,
• cognitive problems, such as a decline in thinking and memory.

Pregnant women who are folate deficient or do not consume enough daily dietary folate or folic acid during the first few weeks of pregnancy have an increased risk of their baby having a birth defect, such as spina bifida (incomplete closure of the spinal cord), anencephaly (misinformation of the brain or skull), congenital heart disease (malformation of the heart), cleft lip and palate (abnormal closure of the lip and palate), problems with the development of the arms and legs, or an abnormal formation of the kidneys or bladder (obstructive uropathies).

Folic acid foods

Folic acid is added to some staple foods to ensure broader access to this crucial vitamin and prevent birth defects. 

• Since 1998, the United States has mandated the fortification of cereal grains with folic acid. Fortified foods high in folic acid are labeled "enriched" and include flour (including corn masa flour used to make corn tortillas) pasta, bread, rice, and breakfast cereal.
• Some other foods also have folic acid added under voluntary fortification rules, but these manufacturers need to follow the FDA food additive regulations.

Certain natural food sources remain excellent sources of folate. Folate-rich foods include:

• Leafy green vegetables such as spinach, kale, collard and mustard greens, and turnip greens.
• Other vegetables including okra, asparagus, and brussels sprouts are good choices.
• Fruits while not as high as vegetables, certain fruits like oranges, papayas, and strawberries contribute folate.
• Beans and legumes such as lentils, black beans, peanuts, black-eyed peas, kidney beans, and chickpeas
• Other folate-containing foods include yeast, mushrooms, animal liver and kidney, orange juice, and tomato juice.

Folic acid supplement side effects

Folic acid side effects are more likely to occur with higher dosages of folic acid (up to 15 mg/day) and include:

• nausea
• loss of appetite
• bloating or gas
• stomach pain
• bitter or unpleasant taste in your mouth
• confusion or trouble concentrating
• sleep problems
• mood changes, such as depression or excitement
• impaired judgment.

Low vitamin B12 levels may occur in patients receiving prolonged folic acid therapy.

Serious side effects and warnings

Folic acid is relatively nontoxic in humans but rare instances of an allergic reaction to folic acid have been reported. You should not use this medication if you have ever had an allergic reaction to folic acid. Get emergency medical help if you have signs of an allergic reaction to folic acid: hives, rash, itching, skin redness, wheezing, difficulty breathing, swelling of your face, lips, tongue, or throat.

May increase the risk of seizures in some people with epilepsy receiving phenobarbital, primidone, or diphenylhydantoin.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Before taking this medicine

You should not use this medicine if you have ever had an allergic reaction to folic acid.

Ask a doctor or pharmacist if this medicine is safe to use if you have ever had:

• epilepsy or other seizure disorder

• cirrhosis or other liver disease

• kidney disease (or if you are on dialysis)

• hemolytic anemia

• pernicious anemia

• anemia that has not been diagnosed by a doctor and confirmed with laboratory testing

• a condition that affects how well you absorb nutrients, such as celiac disease or inflammatory bowel disease

• an infection or

• alcoholism.

Tell your doctor if you are pregnant or breastfeeding. 

These conditions may be causing folate deficiency, require additional medications or a higher dose of folic acid, or further laboratory investigation. For example:

• Folic acid in dosages above 0.4mg daily may hide laboratory changes caused by pernicious anemia without halting the progression of neurological changes. This may result in severe nervous system damage before the correct diagnosis is made.

Pregnancy

Folic acid requirements markedly increase during pregnancy and deficiency will cause harm to the unborn baby. Studies in pregnant women have not shown that folic acid increases the risk of fetal abnormalities if
administered during pregnancy.

Breastfeeding

Folic acid is excreted in the milk of breastfeeding mothers. During lactation, folic acid requirements are
markedly increased; however, amounts present in human milk are adequate to fulfill infant requirements,
although supplementation may be needed in low-birth-weight infants, in those who are breast-fed by
mothers with folic acid deficiency (50 mcg daily), or in those with infections or prolonged diarrhea. 

Fertility

Long-term studies to evaluate the effect of folic acid on fertility have not been conducted.

How should I use folic acid supplements?

Take folic acid exactly as prescribed by your doctor. Do not take it in larger amounts or for longer than recommended. Follow all directions on your medicine label and package. 

Oral administration of folic acid is preferred.

• Although most patients with malabsorption cannot absorb food folates, they can absorb folic acid given orally.
• Administration by injection is not usually recommended but may be necessary for some people receiving parenteral or enteral nutrition.

Folic acid tablets are usually taken by mouth with a full glass of water.

Folic acid injection is given into a muscle, under the skin, or into a vein. A healthcare provider will give you this injection.

Your doctor may occasionally change your dose depending on your blood tests to make sure you get the best results from this medication.

Folic acid is sometimes used in combination with other medications to treat pernicious anemia.

Folic Acid Dosing

Folic acid is an important nutrient and folate or folic acid should be consumed daily. 

• The recommended dietary allowance (RDA) of folic acid for adults is 400 mcg DFE (dietary folate equivalents) daily. 
  • 1 mcg DFE is the same as 1 mcg of folate in food or 0.6 mcg of folic acid supplements. This is because you absorb more from folic acid supplements than you do from food.
• In pregnancy, the RDA of folic acid is 600 mcg DFE daily (some sources recommend 400 to 800 mcg DFE)
• In breastfeeding, the RDA of folic acid is 500 mcg DFE daily.
• In children, the RDA depends on age.
  • Birth to 6 months: 65 mcg DFE
  • Infants 7–12 months: 80 mcg DFE
  • Children 1–3 years: 150 mcg DFE
  • Children 4–8 years: 200 mcg DFE
  • Children 9–13 years: 300 mcg DFE
  • Teens 14–18 years: 400 mcg DFE
  • Adults 19+ years: 400 mcg DFE.

Megaloblastic Anemia

• Adults: 1 mg folic acid once a day.
  • Rule out B12 deficiency.
  • Dosages of up to 5 mg may be used if indicated.
  • May continue until clinical symptoms of folate deficiency and the hematological profile have normalized.

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

What happens if I overdose?

Except during pregnancy and lactation, folic acid should not be given in dosages higher than 0.4 mg daily until pernicious anemia has been ruled out.

Call your healthcare provider, seek emergency medical attention, or call the Poison Help line at 1-800-222-1222 if you take more folic acid than recommended.

What should I avoid while taking folic acid?

Follow your doctor's instructions about any food, beverages, or activity restrictions.

What other drugs will affect folic acid?

Ask a doctor or pharmacist before using folic acid with any other medications, especially:

• methotrexate

• nitrofurantoin

• pyrimethamine

• tetracycline. False low serum and red cell folate levels may occur with some antibiotics that suppress the growth of Lactobacillus casei.

• a barbiturate such as phenobarbital or secobarbital

• seizure medicine such as phenytoin or primidone. The anticonvulsant action of some seizure medications can be antagonized by folic acid and increased dosages of the anticonvulsant may be needed

• sulfasalazine. May reduce the body's ability to absorb folate.

This list is not complete. Other drugs may interact with folic acid, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Storage

Store folic acid at room temperature, away from moisture and heat.

What kinds of folate dietary supplements are available?

Folic acid is available as folic acid supplements and in combination with other vitamins and minerals in multivitamins and prenatal supplements.

Methylfolate (5-MTHF) is another form of folic acid used, which might be better in some individuals with a gene variant called MTHFR C677T because their bodies can use this form more easily. However, this form is not recommended for pregnant women or women who are trying for a pregnancy.

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