Mental Health Home > L-Methylfolate Side Effects

Certain problems may occur while taking L-methylfolate, the active form of folate. Some of the common reactions to this supplement include nausea, sleeping problems, and bloating. There are also potentially serious side effects that may occur with L-methylfolate. Contact your healthcare provider right away if you experience reactions such as confusion, numbness, or difficulty breathing.

Are There Side Effects With L-Methylfolate?

L-methylfolate is the active form of folate, also known as vitamin B9. When used in normal doses, L-methylfolate is usually well tolerated and few people experience side effects. However, it can cause problems in some people, especially at high doses.
(This article discusses most, but not all, side effects of L-methylfolate. Your healthcare provider can discuss a more complete list with you.)

Possible L-Methylfolate Side Effects

Some of the possible side effects of L-methylfolate, especially when used in high doses, include:
  • Sleeping problems
  • Overactivity or excitement
  • Abdominal (stomach) pain
  • Nausea
  • Gas
  • Bloating
  • A bitter or bad taste in the mouth
  • Decreased appetite
  • Change in the color of the urine (it may appear more intense)
  • Problems concentrating
  • Irritability
  • General feelings of discomfort
  • Depression
  • Confusion.

Serious Side Effects

Some L-methylfolate side effects are potentially serious and should be reported immediately to your healthcare provider. These include but are not limited to:
  • Seizures
  • Psychotic behavior
  • Confusion
  • Hair loss
  • Mouth sores or ulcers
  • Numbness, tingling, or pricking feelings in the arms, hands, legs, or feet
  • Signs of an allergic reaction, such as:
    • An unexplained rash
    • Hives
    • Itching
    • Unexplained swelling, especially of the mouth, lips, or throat
    • Wheezing
    • Difficulty breathing or swallowing.
Written by/reviewed by:
Last reviewed by: Kristi Monson, PharmD;
Last updated/reviewed:
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