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Folic acid: 7 things you should know

Medically reviewed by Carmen Fookes, BPharm. Last updated on Mar 19, 2020.

1. How it works

  • Folic acid is one of the B group vitamins; vitamin B9. Folic acid is the synthetic version of vitamin B9 that is found in supplements and fortified foods. Folate is the natural form of vitamin B9 that is found naturally in foods such as asparagus, beans, beets, broccoli, Brussel sprouts, liver, oranges, peas, salmon, spinach, whole-wheat products, and yeast.
  • All of the eight B-vitamins help convert carbohydrates into glucose and help the body to utilize fats and protein. Our brain, eyes, hair, liver, nervous system, and skin require B-vitamins for proper functioning and good health. Folate and folic acid are particularly important during periods of rapid growth and development, such as during pregnancy, in infancy, and in adolescence.
  • Folic acid/folate deficiency is relatively common, particularly among people who regularly drink alcohol, or who have inflammatory bowel disease or Celiac disease. Symptoms of folic acid deficiency include gingivitis, poor appetite, poor growth, neural tube defects in babies, shortness of breath, and tongue inflammation. Folic acid deficiency may also be associated with diarrhea, irritability, forgetfulness, and mental sluggishness.

2. Upsides

  • Folic acid is used to treat folic acid deficiency and certain types of anemia.
  • Folic acid is used in combination with other medications to treat vitamin B12 deficiency (can lead to pernicious anemia).
  • Relatively nontoxic.
  • Folic acid/folate and vitamin B12 are both needed in the production of red blood cells and iron utilization.
  • Folic acid/folate also work with other B-vitamins to control blood levels of the amino acid, homocysteine.
  • Because half of all pregnancies are unplanned, experts recommend all women of child-bearing age consume 0.4 mg (400 micrograms) of folic acid daily. This is to reduce the risk of spina bifida and anencephaly, two common and serious birth defects that may occur within 3-4 weeks of conception (before most women even realize they are pregnant). Following these recommendations dramatically reduces the risk of these birth defects by 72% to 100%. There is some evidence that folic acid supplementation during pregnancy also reduces the risk of miscarriage, autism development, and language delay. Some studies suggest it may protect against age-related hearing loss, age-related macular degeneration, and some forms of cancer. Benefits of folic acid in the treatment of depression are not clear.
  • Consuming recommended levels of folate in the diet may help protect against heart disease, although it is not clear if taking folic acid supplements have the same effect.
  • Generic folic acid is available.

3. Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • Rarely (and more likely with higher dosages): nausea, abdominal pain, skin reactions, sleep problems, loss of appetite, or seizures.
  • High levels of folic acid may mask vitamin B12 deficiency, so talk with your doctor before taking folic acid. Folic acid supplementation is not suitable for people with megaloblastic anemias in which vitamin B12 is deficient.
  • All of the B vitamins, including folic acid, are water-soluble; which means that the body does not store them. A regular intake is required.
  • People with cancer or who have seizures or who take certain medications such as tetracycline (an antibiotic), phenytoin, Daraprim, and some chemotherapy medicines should talk with their doctor before taking folic acid, because of the potential for interactions. Some other medications may interfere with the effectiveness of folic acid.

Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.

4. Bottom Line

Folic acid is the synthetic form of folate (also called vitamin B9) which is necessary for proper growth and development and several other vital bodily processes. All women of child-bearing age should consume 0.4 mg (400 micrograms) of folic acid/folate daily, in the form of folate-rich or fortified foods, or as a supplement.

5. Tips

  • Take folic acid supplements with a full glass of water, either with or without food.
  • Take as directed. Dosages may vary depending on age and pregnancy/breastfeeding status. Do not take more than recommended. If you are taking folic acid because you are deficient in folate, the dosage of folic acid may also decrease as your deficiency reduces.
  • Even if you are not planning on having a baby, if you are a woman of child-bearing age and capability, then you should consume 0.4 mg (400 micrograms) of folic acid daily.
  • If you are concerned about your risk of developing heart disease, ensure your diet contains adequate levels of B vitamins in the form of vitamin B-rich foods.

6. Response and Effectiveness

Folic acid is quickly absorbed and peak levels are reached within an hour of a single dose. Because folic acid is water soluble, the body does not store it, therefore daily intake in the form of folate-containing foods or folic acid supplements is necessary.

7. Interactions

Medicines that interact with folic acid may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with folic acid. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Common medications that may interact with folic acid include:

  • anticonvulsants, such as carbamazepine, divalproex, phenytoin, and phenobarbital
  • chemotherapy agents, such as capecitabine and fluorouracil
  • methotrexate
  • pancreatin and pancrelipase
  • rufinamide.

Note that this list is not all-inclusive and includes only common medications that may interact with folic acid. You should refer to the prescribing information for folic acid for a complete list of interactions.


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.

Copyright 1996-2020 Revision date: March 18, 2020.

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