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Folic acid

Generic name: folic acid [ FOE-lik-AS-id ]
Brand names: FA-8, Folacin-800, FaLessa
Dosage form: oral tablet (0.4 mg; 0.8 mg; 1 mg)
Drug class: Vitamins

Medically reviewed by Melisa Puckey, BPharm. Last updated on Feb 13, 2024.

What is folic acid?

Folic acid is a supplement used to treat folate deficiency, certain types of anemia caused by folic acid deficiency, it is taken by pregnant women to prevent the major birth defects spina bifida and anencephaly, and it is also prescribed with methotrexate to prevent methotrexate-induced folate deficiency. 

Folate vs. folic acid - folic acid is the man-made form of folate (vitamin B9); when you take folic acid, your body turns it into folate. Folate is important for making red blood cells and also for making and maintaining new cells in your body. If your folate levels are low, as shown by a blood test, your healthcare professional may recommend taking folic acid tablets.

Folate deficiency symptoms include feeling tired, heart palpitations, shortness of breath, mouth ulcers, inflamed and painful tongue, depression, irritability, insomnia, and a decline in thinking and memory. Pregnant women who have folate deficiency have an increased risk of their baby having a neural tube defect, which is a birth defect of the spinal cord or brain.

Folate deficiency can be caused by not enough folate in the diet, a problem absorbing folate, or if your body has an increased need for folate, like if you are pregnant or breastfeeding.

Folic acid side effects

Folic acid side effects include nausea, loss of appetite, bloating, gas, stomach pain, bitter or unpleasant taste in your mouth, confusion, trouble concentrating, sleep problems, depression, and feeling Low vitamin B12 levels may occur in patients receiving prolonged folic acid therapy.

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.

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.


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

Before you take folic acid, tell your doctor if you have kidney disease (or if you are on dialysis), an infection, if you are an alcoholic, or if you have any type of anemia that has not been diagnosed by a doctor and confirmed with laboratory testing.

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

Follow all directions on your medicine label and package. Tell each of your healthcare providers about all your medical conditions, allergies, and all medicines you use.

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:

Tell your doctor if you are pregnant or breastfeeding. Your dose needs may be different during pregnancy or while you are breastfeeding.

How should I use folic acid?

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

Folic acid tablets are 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.

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

Folic Acid Dosing information

Usual Adult Folic Acid Dose for Megaloblastic Anemia:

1 mg orally, intramuscularly, subcutaneously or IV once a day. May continue until clinical symptoms of folate deficiency and the hematological profile have normalized.

Usual Adult Dose for Folic Acid Deficiency:

400 to 800 mcg orally, intramuscularly, subcutaneously or IV once a day.

Women of childbearing age, pregnant, and lactating women: 800 mcg orally, intramuscularly, subcutaneously or IV once a day.

Usual Pediatric Dose for Folic Acid Deficiency:

Infant: 0.1 mg orally, intramuscularly, subcutaneously or IV once a day.

Child: Initial dose: 1 mg orally, intramuscularly, subcutaneously or IV once a day.

Maintenance dose: 1 to 10 years: 0.1 to 0.4 mg orally, intramuscularly, subcutaneously or IV once a day.
> 10 years: 0.5 orally, intramuscularly, subcutaneously or IV once a day.

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?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

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:

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.

Popular FAQ

You should take folic acid with methotrexate to help prevent a folate deficiency. Taking methotrexate can lower folate levels in your body and cause symptoms like extreme tiredness, mouth sores, confusion, pale color and weakness. Continue reading

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use folic acid only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.