Folic Acid Side Effects

Folic Acid Side Effects

Folic acid is a water-soluble B vitamin. It is found in many foods – leaf vegetables (spinach, lettuce), meat and offals (liver and kidney), mushrooms, fruits and some cereals. In addition, a small amount of this vitamin is synthesized in the large intestine. However, for the treatment and prevention of certain pathological conditions and for treatment of Folic acid deficiency, a person needs additional amount of Folic acid that cannot be obtained from food.

This vitamin is known for its beneficial effects on metabolism:

  • Protein metabolism, which is the building blocks of all body cells;
  • Purine and pyrimidine bases, which are part of nucleic acids and are responsible for heredity.

The following mechanisms of action of Folic acid are the best known are:

  • Facilitates normal DNA synthesis in cells that are in the process of preparing to divide;
  • Is one of the enzymes that speed up biochemical reactions in the formation of amino acids.

Through these mechanisms, Folic acid provides the following effects in the body:

  • Prevention of congenital malformations in children and neoplasms in adults, by protecting the genetic material from damage;
  • Improvement of the processes of regeneration and renewal of cells in tissues and metabolic rate;
  • Meeting the needs of the fetus, and the growing and developing body;
  • Improvement of the process of hematopoiesis.


It is used to treat Folic acid deficiency, which occurs under such conditions as alcoholism, pregnancy and toxicosis, liver disease, hemolysis, some dermatitis, treatment of certain malignant neoplasms with drugs, dialysis, stomach problems (chronic gastritis), malabsorption in the intestines and celiac disease (gluten intolerance).

Folic acid is also used to treat certain types of anemia (for example, folate-deficiency anemia) and for the prevention of these conditions in people belonging to risk groups.

In addition, Folic acid is prescribed when planning a pregnancy and for the entire gestation period of a child, as well as during breastfeeding. It is important that the suitable dosage is chosen by a doctor.

Side effects

Folic acid is usually very well tolerated and has minimum side effects. Therefore, those few side effects that occur during treatment with this vitamin can be attributed to rare side effects, and the likelihood of their occurrence increases slightly with increasing dose or violation of the rules of taking the vitamin or its dosage.

Side effects of Folic acid include:

  • An unpleasant or bitter taste in the mouth;
  • Nausea, increased bloating, abdominal pain, increased peristalsis, loss of appetite;
  • Sudden changes in mood;
  • A sense of agitation or anxiety;
  • Difficulty falling asleep;
  • Rash.

Notify your doctor if you develop any of the side effects after taking Folic acid.

Serious side effects

The probability of serious adverse reactions to this vitamin is minimal, especially if you follow all the medical advice. However, in rare cases, the following serious side effects may occur:

  • Seizures and convulsive readiness, changes in behavior, depression, and insomnia;
  • Appearance of neoplasms (tumors of the prostate and lung) – several studies showed that neoplasms developed during long-term use of very high doses of Folic acid. However, there is no clear evidence that this disease was caused by the large doses of the vitamin;
  • B-12 deficiency anemia – Folic acid and B12 are joined with the same protein for them to enter the bloodstream, and an excess of one of the vitamins can lead to a deficiency of the other;
  • The development of neurological disorders (eyelid drooping, nystagmus, dizziness, changes in reflexes and sensitivity of individual areas of the body, etc.) during progressive course of B-12 deficiency anemia, other symptoms which were hidden by the use of high doses of Folic acid;
  • Renal impairment because of swelling in the epithelium in the tubules and changes in the flow of urine;
  • Allergic reaction: hives, swelling of the skin, larynx, pharynx, difficulty breathing or swallowing, blisters on the skin, etc.

If you experience any of the serious side effects of Folic acid, urgently seek medical attention.

Laboratory abnormalities

Folic acid can reduce the absorption of vitamin B12, resulting in a change in the external appearance of some blood cells and B12 deficiency anemia.

Side effects in children

Typically, Folic acid can cause side effects in children only when there is substantial excess of the recommended dose. The most common adverse reactions in this case are:

  • Dyspeptic symptoms;
  • Increased irritability;
  • Tearfulness.

One should not also forget about such adverse reaction to this substance as an allergy. Be sure to consult with your doctor before you start giving a child Folic acid, especially if you are doing it the first time or if the child has any allergies.

Side effects during pregnancy and breast-feeding

Doctors often prescribe Folic acid to pregnant women, or to women planning to become pregnant, for the prevention of miscarriage and congenital malformations in children (especially nervous system malformations, neural tube defects, etc.). Under this state of the body, the need for Folic acid increases considerably, and it is prescribed in a much higher dose (400 mg per day and above).

Although Folic acid is safe enough, side effects can still occur under long-term use of very large doses of the vitamin. These side effects are:

  • Development of B-12 deficiency anemia and smoothing of its diagnostically important features, but preservation of neurological manifestations of this condition;
  • Insomnia;
  • Increased irritability, convulsions;
  • Rarely – renal impairment.

You should also know that Folic acid passes into breast milk. Only the doctor chooses the dose, and pregnant or nursing women should fully be aware that one must not prescribe Folic acid without the doctor’s permission. This can either lead to side effects in the expectant mother or in the child, or the vitamin will not have any therapeutic effect if the dose is too small.

Side effects in women

Doctors recommend that women planning to become pregnant should take Folic acid some months before the planned conception at doses close to those prescribed to pregnant women. The benefits of this vitamin in the prevention of pregnancy complications and birth defects are very high. However, one should not forget about the side effects of large doses of Folic acid. Although they are very rare, but one should always remember them and be sure to tell the doctor about all the possible adverse effects such as:

  • Dyspepsia;
  • Nervous agitation, convulsions;
  • Inhibition of vitamin B12 absorption, and anemia;
  • Sleep disorders.

Be sure to consult a specialist in order for him to select the correct dose of the vitamin to minimize the risk of side effects.

Side effects in men

Prophylactic use of Folic acid for men is not as important as for women. It has long been known that this vitamin has a positive effect on sperm quality – improves sperm maturation and reduces the number of sperm cells with damaged genetic material. Usually, high doses of Folic acid are also prescribed to expectant fathers few months before the planned conception. The possible side effects in men are the same as those described above for women. The likelihood of side effects developing in men is also very low. For the safety and efficacy of the vitamin, it is, however, necessary to adhere to the dose recommended by your doctor, and not take this vitamin on your own.

Side effects in the elderly

Older people more often suffer from comorbidities of heart and blood vessels, as well as hyperplastic processes and neoplasms, kidney diseases and other health problems that can trigger side effects. For example, there is evidence of increased risk of a heart attack when this vitamin is used in very high (800 to 1200 mg) doses in people with heart diseases. Therefore, it is advisable to take this vitamin only after consulting a doctor.


There is no evidence confirming that a single use of Folic acid leads to an overdose. However, there is evidence of adverse effects from long-term use (3 or more months) of very large doses of Folic acid. In such cases, there were the following problems:

  • Nausea, vomiting, abdominal pain;
  • Seizures, irritability, insomnia;
  • B-12 deficiency anemia;
  • Renal impairment and changes in the volume and frequency of urination.

While all of these overdose manifestations are extremely rare, it is best to consult your doctor before taking Folic acid in order to select the appropriate dose and for you to avoid possible complications.

Warnings and recommendations

If you are taking any medication, tell your doctor before you start treatment with Folic acid. Some medicines may reduce the effect of this vitamin by preventing its full absorption. For example, such drugs as almagel, phosphalugel, anticonvulsants and oral contraceptives accelerate Folic acid excretion.

If you are planning to become pregnant, you and your partner should together contact the doctor in advance so that the doctor could select the appropriate dose of Folic acid for each of you to prevent pregnancy complications and birth defects in the baby.

Preventive use of Folic acid for pregnant women and women planning a pregnancy who are suffering from epilepsy or diabetes, and for married couples, whose blood relatives have had birth defects is particularly important.

If you have any underlying medical conditions, especially heart problems and blood vessels, or have hyperplastic processes and neoplasms, tell your doctor before you start taking Folic acid in order to avoid side effects.

Folic acid and alcohol

Chronic alcohol intoxication facilitates rapid removal of Folic acid from the body and adversely affects its absorption. While taking this vitamin, rare use of alcohol in limited quantities is not prohibited.