Folic acid dosage, forms, and strengths

Folic acid is a water-soluble vitamin supplement. It’s a synthetic man-made form of folate, an essential nutrient also called vitamin B9. Folate is vital to tissue growth and blood cell production. It is critical in developing a fetus, particularly the nervous system. Most people get enough vitamin B9 in their diet in foods like leafy green vegetables, grain products, and fortified foods, but a deficiency can cause serious medical issues such as anemia. Its critical role in the development of the fetus means that women of childbearing age or pregnant women need to get enough vitamin B9. People at high risk for folate deficiency, pregnant women, and breastfeeding women are often prescribed or advised to take folic acid supplements. 

Folic acid forms and strengths

Some people are advised to take folic acid supplements as tablets, but injections are used in extreme cases. Folic acid is also commonly found in multivitamins, B-complex, children’s, and prenatal vitamins.

• Tablets: 400 micrograms (mcg), 800 mcg, 1 mg

• Injections: 5 mg per milliliter (mL)

Folic acid dosage for adults

Dietary supplements do not normally have a “dosage.” Instead, health professionals recommend a daily intake called the “recommended dietary allowance” or “RDA.” For healthy adults, the RDA for dietary folate is 400 mcg of folate daily. Most people get enough folic acid from foods or food fortification, so supplements aren’t always necessary. However, because of the risk of birth defects, healthcare providers typically advise or prescribe folic acid and other essential nutrient supplements for all women of reproductive age. This helps women have the appropriate folic acid stores during pregnancy or breastfeeding. Healthcare professionals may also prescribe folic acid supplements to people with folate deficiency. Folate deficiency is a cause of a serious blood disorder called megaloblastic anemia. Additional medical uses include managing side effects in people taking methotrexate, preventing folate deficiency in people on hemodialysis, lowering the risk of heart attack or stroke, and treating tropical sprue, a severe form of diarrhea rarely seen in the U.S.

The biologically active form of folate called “L-methylfolate,” or 5-MTHF, may be prescribed to people with a genetic inability to synthesize active folate, a condition called MTHFR polymorphism. Folic acid dosages are not convertible to 5-MTHF doses.

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Folic acid dosage for daily supplementation

People usually get enough folate and folic acid from food, including leafy vegetables, grain products, and fortified foods. However, taking daily supplements containing the recommended dietary allowance of folic acid does not hurt. Higher-dose Vitamin B9 supplements may not have any additional benefit. Remember that the Centers for Disease Control and Prevention (CDC) and the National Institutes of Health (NIH) guidelines are expressed as “dietary folate equivalents.” This is the amount of folate intake that people should consume in foods that contain folate. People only absorb about half the folate in food—only 200 mcg of folate is absorbed from 400 mcg of folate in foods. That’s all that’s necessary. Most adults need only 50 mcg to 100 mcg of folate daily, but they should eat 400 mcg of folate in foods to ensure they get enough folate. However, 400 mcg of folic acid in a tablet equals 400 mcg of folate absorbed into the body—twice as much as from food. So, unless a person has a special need for folate, there’s no need to add supplements. 

• Standard folate RDA for adults: 400 mcg per day

Folic acid supplementation for all women of reproductive age and especially pregnant women

Folate is essential to the development of a fetus. Low folate levels during early pregnancy can cause serious birth defects, including neural tube defects that lead to spina bifida (a spinal cord defect) or anencephaly (a baby missing part of its brain or skull). For the prevention of neural tube defects, the Food and Drug Administration (FDA) and CDC recommend a daily folic acid intake of 600 mcg for pregnant women. Folic acid is an essential ingredient in all prenatal vitamins, so taking prenatal vitamins should meet the daily folate needs of an expecting mother. Because early pregnancy is a critical stage of fetal development, all women of childbearing age should make sure they get the standard recommended dietary allowance of folate every day, even when not pregnant.

• Standard folate RDA for pregnant women: 600 mcg per day

Folic acid supplementation for lactating women

The CDC recommends a higher daily folic acid intake to ensure a breastfeeding woman and the nursing infant get enough folate.

• Standard folate RDA for breastfeeding women: 500 mcg per day

Folic acid dosage for megaloblastic anemia

A deficiency in either vitamin B9 or vitamin B12, or both, can lead to impaired production of red blood cells, resulting in a condition known as megaloblastic anemia. Other problems can cause this condition, but if a folate deficiency is a contributing cause, treatment will consist of folic acid supplements and other supplements, including vitamins B6 and B12. Most people will take oral tablets, but people who can’t absorb the nutrient will be given injections. Supplementation can stop when the deficiency has been corrected, but some people require lifelong maintenance supplementation.

• Standard folic acid dosage for adults with megaloblastic anemia due to folate deficiency: 1 mg per day

• Maintenance folic acid dosage for adults who have recovered from megaloblastic anemia: At least 0.1 mg per day

Folic acid dosage for methotrexate therapy

Methotrexate, a common treatment for rheumatoid arthritis, is an antifolate drug that blocks the effects of folic acid. Between 7% and 30% of people taking methotrexate quit the drug because of side effects. A rheumatologist or other healthcare professional may suggest taking folic acid supplements to reduce methotrexate side effects or help prevent a folate deficiency. There is no standard dosage or agreement about taking folic acid on the same day as a methotrexate dose. 

• Suggested folic acid dosage for adults on methotrexate therapy: 5 mg taken once per week but not on the same day as methotrexate doses OR 1 mg taken daily OR 1 mg taken 24 or 48 hours before a methotrexate dose

Folic acid supplementation for dialysis

Hemodialysis removes folate from the blood, so people on chronic hemodialysis may be asked to take folic acid and other supplements. Healthcare providers may suggest 1 mg to 5 mg daily.

Folic acid supplementation to prevent heart attack and stroke

Some cardiologists and other healthcare professionals believe that folic acid supplementation, along with other vitamin supplements, decreases the risk of heart attack or stroke in people with risk factors for these conditions. Evidence doesn’t fully support this, but folic acid supplements reduce homocysteine levels in the blood. This is considered important because high homocysteine levels increase the risk of heart attack and stroke. The amount of folic acid taken daily has not been standardized, so dosage recommendations depend on individual practitioners.

Folic acid dosage for children

As an essential nutrient, folate should be a normal part of every child’s diet. A healthy and well-balanced diet is enough to supply a child’s needs. Adding folate-fortified foods like breakfast cereals increases the likelihood of a child getting enough folate. If diet is a concern, children’s multivitamins could help as long as children don’t have access to a bottle.

• Standard folate RDA for children from newborns to 6 months: 65 mcg per day

• Standard folate RDA for children from 7 months to 12 months: 80 mcg per day

• Standard folate RDA for children from 1 to 3 years of age: 150 mcg per day

• Standard folate RDA for children from 4 to 8 years of age: 200 mcg per day

• Standard folate RDA for children from 9 to 13 years of age: 300 mcg per day 

• Standard folate RDA for children from 14 to 18 years of age: 400 mcg per day

Adolescents who are pregnant or breastfeeding will require the same RDA of folate as pregnant or lactating women.

Daily doses for children treated for megaloblastic anemia are the same as for adults: 1 mg daily.

Folic acid dosage restrictions

As a nutrient, there are no dosage restrictions for people with kidney problems, liver impairment, or advanced age. No dosage adjustments are required.

Folic acid dosage for pets

According to Plumb’s Veterinary Manual, folic acid is used in either folate-deficient pets or on antifolate drugs. Doses and treatment duration will depend on the underlying cause of folate deficiency, such as dietary problems, inflammatory bowel disease (IBD), exocrine pancreatic deficiency, or high-dose trimethoprim-sulfamethoxazole treatment. 

• Standard folic acid dosage for dogs and cats: 0.4–2 mg per day

How to take folic acid

Like other supplements, folic acid supplements are usually taken once per day, with or without food. When folic acid is taken without food, the entire dose is absorbed by the body. Slightly less (85%) is absorbed when folic acid supplements are taken with a meal. 

• Follow the instructions written on the packaging or given to you by a doctor.

• Do not exceed the suggested RDA or dosage.

• Swallow the tablets whole with a full glass of water.

• A missed dose of folic acid can be taken on the same day. If it’s the next day, skip the missed dose and take the tablet scheduled for that day. 

• Store folic acid supplements in a childproof container at room temperature, protected from light and moisture.

Folic acid dosage FAQs

How long does it take folic acid to work?

For daily supplementation, folic acid supplements will establish normal folate levels and blood counts quickly. For megaloblastic anemia, blood problems return to normal quickly with the appropriate treatment or supplements. Nervous system problems may take longer to resolve. 

How do I stop taking folic acid?

For daily supplementation, anyone on a well-balanced and healthy diet can stop folic acid supplements at any time. There are no withdrawal effects. If a healthcare provider has prescribed the supplement, take it for the entire duration prescribed.

What is the maximum dosage for folic acid?

The National Institutes of Health Office of Dietary Supplements advises healthy people not to exceed the recommended dietary allowance. Doses may be higher than the RDA for people with certain medical conditions.

Can you overdose on folic acid?

Taking too much folic acid provides no benefit. Do not exceed the daily RDA unless instructed to by a doctor.

What interacts with folic acid?

There are very few folic acid drug interactions. The most important are drugs that block folate, such as the anticonvulsant phenytoin. Folic acid supplements may decrease the effectiveness of these drugs. 

What happens when you mix folic acid and alcohol?

Alcohol consumption is a common cause of folate deficiency. Alcohol interferes with the body’s ability to absorb folate or folic acid. People who need folic acid supplements should avoid drinking alcohol.

Is it safe to take folic acid during pregnancy?

Yes. All women of reproductive age should take a prenatal vitamin containing folate. Pregnant women and breastfeeding women are encouraged to take folic acid supplements during pregnancy and lactation. Not only are folic acid supplements safe to take, but they also help protect the fetus from serious, life-long birth defects.

Sources

• Folate fact sheet for health professionals, NIH Office of Dietary Supplements

• Folic acid tablet prescribing information, NIH National Library of Medicine

• Megaloblastic anemia, StatPearls

• Methotrexate: managing side effects, Arthritis Foundation