Merck Manual

Please confirm that you are not located inside the Russian Federation

Loading

Folate Deficiency

(Folic Acid Deficiency)

By

Larry E. Johnson

, MD, PhD, University of Arkansas for Medical Sciences

Last full review/revision Oct 2019| Content last modified Oct 2019
Click here for the Professional Version
NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Topic Resources

Folate deficiency is common. Because the body stores only a small amount of folate, a diet lacking in folate leads to a deficiency within a few months.

  • Not eating enough raw leafy vegetables and citrus fruits can cause folate deficiency.

  • Anemia can develop, causing fatigue, paleness, irritability, shortness of breath, and dizziness.

  • A severe deficiency may result in a red and sore tongue, diarrhea, a reduced sense of taste, depression, confusion, and dementia.

  • If a pregnant woman has folate deficiency, the risk of having an infant with a birth defect of the spinal cord or brain is increased.

  • The diagnosis is based on blood tests.

  • Folate supplements taken by mouth usually correct the deficiency.

Folate is a B vitamin. Along with vitamin B12, folate is necessary for the formation of normal red blood cells and the synthesis of DNA (deoxyribonucleic acid), which is the genetic material of cells. Folate is also necessary for normal development of a fetus’s nervous system.

Good sources of folate include raw green leafy vegetables, asparagus, broccoli, fruits (especially citrus), liver, other organ meats, dried yeast, and enriched breads, pastas, and cereals. Extensive cooking destroys 50 to 95% of the folate in food.

In the United States and Canada, folate is added to enrich foods made from grains. Folate in supplements or in enriched foods is easier for the body to absorb than the folate that occurs naturally in food.

Women who are pregnant or who could become pregnant should take folate supplements to reduce the risk of having an infant with a birth defect, mainly neural tube defects. Women who have had a baby with a neural tube defect are often prescribed higher doses of folate.

Women who are taking both oral contraceptives and antiseizure drugs may need to take folate supplements. Antiseizure drugs can make oral contraceptives less effective. Folate supplements can help maintain the effectiveness of oral contraceptives.

Folate supplements do not protect against coronary artery disease or stroke. There is no evidence that folate supplements reduce or increase the risk of various cancers. Folate supplements do not seem to improve cognitive function in older adults.

Folate is generally not toxic.

Causes

Folate deficiency may result from

  • Inadequate consumption of folate (usually in people who drink too much alcohol or are undernourished)

  • Impaired absorption (malabsorption disorders such as celiac disease or certain drugs)

  • An increased need for folate (for example due to pregnancy or breastfeeding)

People who drink large amounts of alcohol do not consume enough folate because they often substitute alcohol for food. Such people are often generally undernourished. Alcohol consumed in large amounts also interferes with the absorption and processing (metabolism) of folate.

Malabsorption disorders (such as celiac disease) interfere with absorption of folate.

Women who are pregnant or breastfeeding and people undergoing dialysis may develop this deficiency because their need for folate is increased.

Some drugs decrease the absorption of this vitamin. They include

Other drugs interfere with the metabolism of folate. They include

  • Methotrexate (used to treat cancer and rheumatoid arthritis)

  • Triamterene (used to treat high blood pressure)

  • Metformin (used to treat diabetes)

  • Trimethoprim-sulfamethoxazole (an antibiotic)

Symptoms

Folate deficiency results in anemia that develops gradually and may be more severe than symptoms suggest. Fatigue may be the first symptom.

In addition to the general symptoms of anemia (such as paleness, irritability, shortness of breath, and dizziness), folate deficiency, if severe, may result in a red and sore tongue, diarrhea, a reduced sense of taste, weight loss, and depression.

If a pregnant woman has folate deficiency, the risk of having an infant with a birth defect of the spinal cord or brain (neural tube defect) is increased.

Did You Know...

  • If a pregnant woman has folate deficiency, her risk of having an infant with a birth defect of the brain or spinal cord is increased.

Diagnosis

  • Blood tests

If a blood test detects large red blood cells in people who have anemia or who are undernourished, doctors measure the folate level in a blood sample. A low level indicates folate deficiency.

Doctors also measure the vitamin B12 level to rule out vitamin B12 deficiency because this deficiency can also result in anemia and large red blood cells. Doctors must rule out vitamin B12 deficiency before they treat folate deficiency in people with anemia. If people with vitamin B12 deficiency are treated with folate, the anemia may lessen. But folate supplementation does not relieve the nerve damage due to vitamin B12 deficiency and may even make it worse.

Prevention and Treatment

  • Folate supplements

To help prevent folate deficiency, people who are taking drugs that interfere with the absorption or metabolism of folate should take a folate supplement.

Taking daily doses of a folate supplement by mouth effectively treats the deficiency.

Drugs Mentioned In This Article

Generic Name Select Brand Names
AZULFIDINE
No US brand name
OTREXUP
DYRENIUM
GLUCOPHAGE
DILANTIN
NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read

Also of Interest

Videos

View All
Overview of Vitamins and Minerals
Video
Overview of Vitamins and Minerals
The human body needs various vitamins and minerals in order to thrive. Many of these nutrients...
Roux-en-Y Gastric Bypass
Video
Roux-en-Y Gastric Bypass
The digestive process begins in the mouth, where chewing and saliva breakdown food. Digestion...

SOCIAL MEDIA

TOP