Folic Acid Side Effects

While most people do not experience problems when taking folic acid, side effects may occur if you take high doses of the vitamin. It is also possible to develop an allergic reaction while taking it. If taken in high doses, side effects of folic acid may include stomach cramps, gas and bloating, diarrhea, and problems sleeping.

 

Does Folic Acid Cause Side Effects?

Folic acid usually does not cause significant side effects in most people, especially when taken at normal dosages. However, folic acid can sometimes cause serious side effects, especially when taken at higher dosages.
 
(This article covers many, but not all, of the possible side effects with folic acid. Your healthcare provider can discuss a more complete list of folic acid side effects with you.)
 

Possible Side Effects of Folic Acid

Taking high doses of folic acid, more than 1 mg (1000 mcg) a day, can "mask" a vitamin B12 deficiency.
 This means that folic acid can correct anemia caused by vitamin B12 deficiency (making the deficiency hard to detect or diagnose), but it does not stop the nerve damage caused by the vitamin B12 deficiency.
 
Very high doses have been reported to cause the following folic acid side effects:
 
  • Abdominal (stomach) cramps
  • Diarrhea
  • Nausea
  • Gas and bloating
  • Rash
  • Problems sleeping
  • Irritability, excitability, or hyperactivity
  • Bitter taste in the mouth
  • Zinc deficiency
  • Psychotic behavior
  • Seizures (typically in people who already have a seizure disorder).
     
Early studies suggest that high doses of folic acid might actually increase the risk of cancer, cardiovascular disease, or age-related cognitive problems. A normal folic acid dosage does not seem to be associated with such problems.
 
Even though folic acid is added to a wide variety of foods in the United States, some people may be allergic to it. Seek medical attention right away if you develop any signs of an allergic reaction, such as:
 
  • An unexplained rash
  • Hives
  • Itching
  • Swelling of the mouth or throat
  • Wheezing
  • Difficulty breathing or swallowing.
 
(Folic Acid Side Effects Continued: Page 2)
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Written by/reviewed by: Kristi Monson, PharmD; Arthur Schoenstadt, MD
Last reviewed by: Kristi Monson, PharmD;