Folic acid is used to treat or prevent folic acid deficiency. It is a B-complex vitamin needed by the body to manufacture red blood cells. A deficiency of this vitamin causes certain types of anemia (low red blood cell count).
Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
The effectiveness ratings are as follows:
- Folate deficiency. Taking folic acid improves folate deficiency.
Likely effective for…
- Serious kidney disease (end-stage renal disease or ESRD). About 85% of people with serious kidney disease have high levels of homocysteine. High levels of homocysteine have been linked to heart disease and stroke. Taking folic acid lowers homocysteine levels in people with serious kidney disease. However, supplementation does not appear to reduce the risk of heart disease-related events.
- High amounts of homocysteine in the blood (hyperhomocysteinemia). High levels of homocysteine have been linked to heart disease and stroke. Taking it lowers homocysteine levels by 20% to 30% in people with normal to slightly elevated homocysteine levels. It is recommended that people with homocysteine levels are greater than 11 micromoles/L supplements with folic acid and vitamin B12.
- Toxicity caused by the drug methotrexate. Taking folic acid seems to reduce nausea and vomiting, which are possible side effects of methotrexate treatment.
- Birth defects of the brain and spine (neural tube birth defects). Folic acid during pregnancy reduces the risk of neural tube birth defects. It is recommended that pregnant women get 600-800 mcg per day from their diet or supplements starting 1 month before pregnancy and during pregnancy. Pregnant women with a history of neural tube birth defects are advised to get 4000 mcg per day.
Possibly effective for…
- An eye disease that leads to vision loss in older adults (age-related macular degeneration or AMD). Research shows that taking it with other vitamins including vitamin B6 and vitamin B12 reduces the risk of developing age-related vision loss.
- The decline in memory and thinking skills in older people is more than what is normal for their age. Research shows that taking it with or without other B vitamins may improve memory and thinking skills in older people with larger than normal declines in these skills. Folic acid seems to work best in people who have low levels of folate or high levels of homocysteine in the blood.
- Depression. Limited research shows that taking folic acid along with antidepressants seems to improve symptoms in people with depression.
- High blood pressure. Research shows that taking folic acid daily for at least 6 weeks reduces blood pressure in people with high blood pressure. But taking it with blood pressure medication does not seem to lower blood pressure more than taking only blood pressure medicine.
- Gum enlargement caused by the drug phenytoin. Applying folic acid to the gums seems to prevent gum problems caused by phenytoin. However, taking it by mouth does not seem to improve the symptoms of this condition.
- Gum disease in women who are pregnant. Applying folic acid to the gums seems to improve gum disease during pregnancy.
- Stroke. Taking folic acid can reduce the risk of stroke by 10% to 25% in people who live in countries that don’t fortify grain products with folic acid. But it doesn’t seem to prevent strokes in most people who live in countries that do fortify grain products with folic acid.
- A skin disorder that causes white patches to develop on the skin (vitiligo). Taking folic acid by mouth seems to improve symptoms of vitiligo.
Possibly ineffective for…
- Low levels of healthy red blood cells (anemia) due to iron deficiency. Taking folic acid with iron supplements is not more effective than taking iron supplements without folic acid for treating and preventing iron deficiency and anemia caused by too little iron in the body.
- A decline in memory and thinking skills occurs normally with age. Most research shows that taking it does not prevent the decline in memory and thinking skills in the elderly.
- A procedure to open a blocked or narrowed blood vessel (angioplasty). There is inconsistent evidence on the benefits of taking folic acid after a procedure to widen the blood vessels. But taking folic acid plus vitamin B6 and vitamin B12 might actually interfere with healing in cases where a device (stent) is inserted in the blood vessel to keep it open.
- Breast cancer. Consuming folate in the diet might lower the risk of developing breast cancer in women who also eat high amounts of methionine, vitamin B12 (cyanocobalamin), or vitamin B6 (pyridoxine), but research is not consistent. Other research suggests that taking supplements alone does not lower the risk of breast cancer.
- Cataracts. Research shows that taking folic acid with other vitamins including vitamin B6 and vitamin B12 does not prevent cataracts. In fact, it might increase the chance of needing to have cataracts removed.
- Chronic fatigue syndrome (CFS). Daily injections appear to have no effect on symptoms of chronic fatigue syndrome.
- Diarrhea. Taking a specific nutritional supplement with added folic acid and possibly vitamin B12 does not seem to prevent diarrhea in children at risk of malnutrition. Taking this product may increase the risk of having diarrhea last more than a few days.
- Fall prevention. Taking it with vitamin B-12 does not seem to prevent falls in older people who are also taking vitamin D.
- Death of an unborn or premature baby. Taking folic acid during pregnancy does not seem to reduce the risk of having a baby die just before or after birth.
- Cancer of the white blood cells (leukemia). Taking folate during pregnancy does not reduce the risk of childhood cancer of the white blood cells.
- Toxicity from the drug lometrexol. Taking it by mouth does not seem to reduce the harmful effects of the drug lometrexol.
- Weak and brittle bones (osteoporosis). In elderly individuals with osteoporosis, taking folic acid with vitamin B12 and possibly vitamin B6 (pyridoxine) does not seem to prevent broken bones.
- Physical performance in elderly adults. Taking it with vitamin B-12 doesn’t seem to help older people walk better or have stronger hands.
- Infection of the airways. Taking a specific nutritional supplement with added folic acid and possibly vitamin B12 does not seem to prevent infections in the lungs in children at risk of malnutrition.
Likely ineffective for…
- Non-cancerous growths in the large intestine and rectum (colorectal adenoma). Taking supplements does not seem to prevent growth in the large intestine or rectum.
- An inherited condition marked by learning disabilities (fragile-X syndrome). Taking folic acid by mouth does not improve symptoms of fragile-X-syndrome.
- Preterm birth. Taking it during pregnancy does not decrease the risk of having a premature baby.
Insufficient evidence to rate effectiveness for…
- Alzheimer disease. Some limited evidence has found that elderly people who consume more folic acid in the diet or from supplements appear to have a lower risk of developing Alzheimer’s disease than people who consume less folic acid. But this has not been confirmed in good quality studies. Early research also shows that taking folic acid along with other B vitamins might slow declines in memory, thinking, behavior, and activities of daily living in people with Alzheimer’s disease who are taking drugs for Alzheimer’s disease called cholinesterase inhibitors.
- Autism. Limited research suggests taking it during pregnancy might reduce the risk of autism in the child.
- A blood disorder that reduces levels of protein in the blood called hemoglobin (beta-thalassemia). Beta-thalassemia is a disorder of the blood that results in the production of less hemoglobin, the protein that carries oxygen in the blood. Patients with beta-thalassemia usually have bone and muscle pain and have less strength. In children with this disorder, limited research suggests taking it by itself, or with L-carnitine, a compound similar to an amino acid from protein, might reduce bone pain and help increase strength.
- Bipolar disorder. Taking folic acid does not appear to improve the antidepressant effects of lithium in people with bipolar disorder. However, taking folate with the medication valproate improves the effects of valproate.
- Heart disease. Some research shows that taking folic acid doesn’t reduce the risk of death in people with heart disease. But it might reduce the risk of stroke in people with this condition.
- Cancer of the cervix. There is some evidence that increasing folic acid and folate intake from dietary and supplement sources, along with thiamine, riboflavin, and vitamin B12, might help to prevent cancer of the cervix.
- Child development. Some research shows that taking folic acid supplements during the last 22 weeks of pregnancy may improve the child’s mental function during childhood.
- Long-term kidney disease (chronic kidney disease or CKD). Taking folic acid might help slow kidney function decline in people with CKD. But it is not beneficial when used along with vitamin B12 (cyanocobalamin). In fact, this combination might make kidney disease worse.
- Colon cancer, rectal cancer. Research suggests that taking folic acid or eating folate in the diet can reduce the risk of developing colon or rectal cancer. However, there is some research that does not suggest that taking folic acid or folate in the diet offers the same benefit. It is possible that it may be more helpful for preventing colon cancer than rectal cancer or it may be more helpful for specific kinds of colon cancer.
- Heart problems at birth. Women who take folic acid or prenatal vitamins containing folic acid have a lower chance of giving birth to babies with heart problems.
- Diseases, such as Alzheimer’s disease, that interfere with thinking (dementia). Some research shows that folic acid might help prevent or treat Alzheimer’s disease. But other early research shows that it might not be useful for treating other types of dementia.
- Diabetes. Taking folic acid supplements does not seem to benefit people with diabetes.
- Epilepsy. Taking folic acid does not reduce seizures in people with epilepsy. But some early research suggests that folic acid might reduce seizures in children that are deficient.
- Cancer of the esophagus. Research suggests that consuming more folate in the diet lowers the risk of developing cancer of the esophagus.
- High amounts of homocysteine in the blood caused by the drug fenofibrate. Taking folic acid every other day might lower levels of homocysteine in the blood caused by the drug fenofibrate.
- Stomach cancer. Research suggests that taking it reduces the risk of developing some types of stomach cancer.
- Gout. Early research suggests that folate might reduce the risk of gout.
- Head and neck cancer. Getting more folic acid from the diet has been linked to a lower risk of head and neck cancer.
- Hearing loss. Low levels of folate in the blood seem to be related to the risk for sudden hearing loss in adults. Some evidence suggests that taking folic acid daily for 3 years slows the decline of hearing loss in older people who have low folate levels. It is not clear if supplementation reduces hearing loss in people with normal folate levels.
- Infants born weighing less than 2500 grams (5 pounds, 8 ounces). Taking folic acid during pregnancy does not prevent some babies from being born at a low birth weight but it does seem to increase the overall average of birth weights. However, some early research suggests that taking it before getting pregnant might reduce the risk of having a baby that is too small even when born full term. Although this risk is not reduced in mothers that start supplementation after the baby is conceived.
- Lung cancer. There does not appear to be a relationship between low levels and lung cancer in most people.
- The most serious type of skin cancer (melanoma). Early research shows that taking folic acid might reduce the risk of melanoma.
- The reduced benefit of nitrate therapy happens when nitrates are used all day (nitrate tolerance). Some evidence suggests that taking folic acid does not help medications for chest pain (nitrates) work longer.
- Cleft lip and cleft palate. Some research suggests that taking folic acid during pregnancy lowers the risk of cleft lip. However, other research shows no effect.
- Pancreatic cancer. Eating more than 280 mcg of folate in the diet daily is linked to a lower risk of developing pancreatic cancer. However, other research suggests that folate intake is not linked to pancreatic cancer risk.
- A type of throat cancer (pharyngeal cancer). Limited research suggests folic acid and folate from dietary and sources and supplements may protect against oropharyngeal cancer, a specific type of throat cancer.
- A pregnancy complication marked by high blood pressure and protein in the urine (pre-eclampsia). Pre-eclampsia is marked by high blood pressure and protein in the urine during pregnancy. Research regarding whether folic acid reduces the risk of pre-eclampsia is conflicting.
- High blood pressure during pregnancy. Limited research found that taking folic acid during pregnancy does not reduce the risk of high blood pressure.
- A disorder that causes leg discomfort and an irresistible urge to move the legs (restless legs syndrome or RLS). Taking folic acid seems to reduce symptoms of restless legs syndrome. Researchers are studying whether deficiency causes restless legs syndrome.
- Schizophrenia. Taking a combination of folic acid and vitamin B12 may reduce some of the negative symptoms associated with schizophrenia, but only in some patients with a specific genetic make-up. In most people, it does not help with these symptoms.
- Sickle-cell disease. Taking folic acid might lower homocysteine levels. However, it is not known if this will benefit people with sickle-cell disease.
- Eczema (atopic dermatitis).
- Liver disease.
- Male infertility.
- Nerve pain in people with diabetes (diabetic neuropathy).
- Nerve damage in the hands and feet (peripheral neuropathy).
- Other conditions.
More evidence is needed to rate folic acid for these uses.
Side Effects Of Folic Acid
Folic acid may cause side effects. If you experience any of the following symptoms, call your doctor immediately:
- skin rash
- difficulty breathing
When taken by mouth:
Folic acid is LIKELY SAFE for most people. Most adults do not experience any side effects when taking doses of less than 1 mg daily.
Folic acid is POSSIBLY UNSAFE when taken by mouth in large doses, long-term. Although doses up to 5 mg daily have been safely used in some research, doses greater than 1 mg daily might cause abdominal cramps, diarrhea, rash, sleep disorders, irritability, confusion, nausea, stomach upset, behavior changes, skin reactions, seizures, gas, excitability, and other side effects.
There is also some concern that taking too much folic acid for a long period of time might cause serious side effects. Some research suggests that taking it in doses of 800 mcg to 1.2 mg daily might increase the risk of a heart attack in people who have heart problems. Other research suggests that taking these high doses might also increase the risk of cancer such as lung or prostate cancer.
When given as a shot:
Folic acid is LIKELY SAFE for most people when injected into the body. Most adults do not experience any side effects when used in doses less than 1 mg daily.
Warnings & Precautions
- Pregnancy and breast-feeding: Folic acid is LIKELY SAFE when taken by mouth appropriately when pregnant or breast-feeding. Taking 300-400 mcg daily is commonly used during pregnancy to prevent birth defects. The maximum recommended amount of folic acid for pregnant or breast-feeding women is 800 mcg per day for women under 18 years of age and 1000 mcg per day for women over 18 years of age.
- Children: Folic acid is LIKELY SAFE when taken by mouth in the recommended amounts for each age group. But children should avoid taking doses above the daily upper limits, which are 300 mcg for children 1-3 years of age, 400 mcg for children 4-8 years of age, 600 mg for children 9-13 years of age, and 800 mcg for children 14-18 years of age.
- Procedures to widen narrowed arteries (angioplasty): Using folic acid, vitamin B6, and vitamin B12 intravenously (by IV) or by mouth might worsen narrowed arteries. Folic acid should not be used by people recovering from this procedure.
- Cancer: Early research suggests that taking 800 mcg to 1 mg of folic acid daily might increase the risk of cancer. Until more is known, people with a history of cancer should avoid high doses of folic acid.
- Heart disease: Early research suggests that taking folic acid plus vitamin B6 might increase the risk for heart attack in people with a history of heart disease.
- Malaria: Early research suggests that taking it plus iron might increase the risk of death or need for treatment in hospitals in areas of the world where malaria is common.
- Anemia caused by vitamin B12 deficiency: Taking it might mask anemia caused by vitamin B12 deficiency and delay appropriate treatment.
- Seizure disorder: Taking folic acid supplements might make seizures worse in people with seizure disorders, particularly in high doses.
Before taking folic acid:
- tell your doctor and pharmacist if you are allergic to folic acid or any other drugs.
- tell your doctor and pharmacist what prescription and nonprescription medications you are taking, especially phenytoin (Dilantin) and vitamins.
Dosage Of Folic Acid
Folic acid comes in tablets. It usually is taken once a day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take it exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.
If you are taking folic acid to treat a deficiency, you probably will feel better quickly, often within 24 hours. However, do not stop taking this drug until your doctor tells you to do so.
Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your response to folic acid.
Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.
It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.
All information has been provided courtesy of MedLinePlus from the National Library of Medicine and from the FDA.