Folic acid side effects and how to avoid them (2023)

Common folic acid side effects| Serious side effects | Allergic reactions | Seizures | Side effects timeline| Contraindications | Warnings | Interactions | How to avoid side effects| How to treat side effects

Folic acid (or folacin) is a synthetic form of folate, an essential nutrient also known as vitamin B-9. Folate is found in leafy green vegetables, fruits, cereals, and grain products, but some people may need to take folic acid supplements. Healthcare providers may prescribe folic acid as a tablet or injection for certain types of anemia, or for people who are malnourished, young, or pregnant.

The body needs folate to grow new cells. This includes skin, hair, and, most importantly, blood. Large red blood cells (megaloblastic anemia) are often the first serious consequence of a folic acid deficiency. Folate is also important to the development of a fetus, particularly for the nervous system. A folate deficiency early in pregnancy could cause serious birth defects such as spina bifida and anencephaly. Folic acid supplements are strongly encouraged during pregnancy. Side effects of folic acid supplements are relatively rare and mild.

Common side effects of folic acid

Side effects due to folic acid are rare. Hypersensitivity reactions may include:

  • Skin rash or redness
  • Itching
  • Feeling bad
  • Trouble breathing

Digestive system problems have also been reported in people taking high-dose folic acid. Though rare, these include:

  • Appetite loss
  • Nausea
  • Flatulence
  • Bloating
  • Taste changes

Other rare adverse effects reported by people taking high-dose folic acid include:

  • Irritability
  • Excitement
  • Overactivity
  • Depression
  • Sleep problems
  • Confusion
  • Difficulty concentrating

Serious side effects of folic acid

The most serious side effects of folic acid are allergic reactions. These include:

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  • Airway closure (bronchospasm)
  • Anaphylaxis

Folic acid and allergic reactions

Though rare, the most common side effects are allergic reactions to folic acid or some other ingredient in the supplement. The incidence has not been determined. Some have only been reported in people taking excessively high doses of 15 mg or more, which is 35 times the recommended daily allowance.

Folic acid and seizures

There is a myth that folic acid might cause seizures. Seizures can occur rarely when large doses of folic acid are taken by people with epilepsy who are also taking primidone, phenobarbital, phenytoin, or diphenylhydantoin. In these cases, the seizures are due to a drug interaction that lowers the level of antiseizure medication in the body. The seizures are not a side effect of folic acid itself. On the contrary, people taking antiepileptic drugs frequently have low folate levels in their blood. Folic acid supplementation has been shown to improve seizure control.

How soon do folic acid side effects start?

Since many of the side effects of folic acid are allergic reactions, they typically start early in treatment or right after taking a pill or getting an injection. Digestive system problems also tend to occur within the first month of high-dose folic acid treatment. However, mood problems, depression, and confusion are usually delayed reactions.

How long do folic acid side effects last?

Hypersensitivity reactions will continue for as long as folic acid—or a particular folic acid product—is used. They may even worsen if the supplement isn’t stopped. Side effects caused by high-dose folic acid therapy should clear up when doses are returned to normal.

What are the long-term side effects of folic acid?

Prolonged use of folic acid supplements could reduce the levels of vitamin B12 (cobalamin) in the blood. In addition, prolonged folic acid use can hide the symptoms of vitamin B12 deficiency. Like folate, cobalamin is vital to the growth and reproduction of cells. A cobalamin deficiency can lead to pernicious anemia, the condition that helps healthcare professionals diagnose a B12 deficiency. But a B12 deficiency can also permanently damage nerves and the spinal cord. Prolonged use of folic acid can cover up pernicious anemia, so the damage to the nervous system caused by a B12 deficiency could continue undetected.

Folic acid contraindications

Folic acid is never given to people who are allergic to it.


Folic acid is not only safe to take by pregnant women, but it is strongly recommended. Folate is so important to the neural development of a fetus, the CDC suggests that women of childbearing age get at least 400 micrograms (mcg) of folate per day either by eating fortified foods or taking folic acid supplements. A healthcare provider may suggest a higher intake of folate before conception and during pregnancy. In women who have been pregnant with a fetus that had neural tube defects, the CDC suggests 4,000 mcg (4 mg) per day for one month before anticipated conception and for three months after conception.

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RELATED: Why pregnant women need to take folic acid


Folic acid is safe and recommended while breastfeeding. Recommendations may vary, but the minimum intake should be 400 mcg per day. Since folate is present in breast milk as a vital nutrient for the nursing infant, some healthcare professionals recommend a higher daily intake to make up for the folate being lost in the milk. Folate from the diet is present in human breast milk, but so is folic acid taken in supplements. Like folate, folic acid is considered nontoxic for the nursing child.


It is safe to give children folic acid supplements following recommended guidelines. Prescription folic acid is approved by the U.S. Food and Drug Administration (FDA) in children as young as 1 month old.


People older than 65 can take over-the-counter and prescription folic acid safely if they follow recommended guidelines or the instructions of a healthcare provider.

Folic acid warnings

Since folic acid is not toxic, it has only a few warnings and cautions.


Because folic acid can mask pernicious anemia due to a vitamin B12 deficiency, healthcare providers are unlikely to prescribe folic acid supplements to people with a vitamin B12 deficiency, pernicious anemia, or undiagnosed anemia.

People who are considering over-the-counter folic acid supplements should take the recommended daily allowance of 400 mcg per day. They should also make sure to take the recommended daily allowance of vitamin B12. Anyone who suspects they have some type of anemia or vitamin deficiency should get medical advice from a healthcare professional before taking supplements.

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Abuse and dependence

Folic acid does not cause physical dependence or withdrawal. Some people do take high doses of vitamins for a variety of motivations, but this is not considered drug abuse.


Call a poison control center or get emergency medical attention if too much folic acid is taken. Except under the instructions of a healthcare professional, the maximum daily folate intake should not exceed 400 mcg.

Folic acid interactions

Although folic acid is a vitamin, it does have a few important drug interactions. Most are mild, but healthcare providers may have to adjust doses or find other treatments.

  • Seizure medications: Folic acid reduces the concentrations of certain types of anticonvulsants in the body, making seizures more likely.
  • Alcohol: Alcohol partly blocks the ability of the intestines to absorb folic acid. Many people who abuse alcohol have folate deficiency.
  • Bile acid resins: Like alcohol, bile acid sequestrants used to treat high cholesterol reduce the body’s absorption of folic acid through the intestines.
  • Methotrexate: Folic acid can reduce the effectiveness of the immune suppressant methotrexate. However, because folic acid competes with methotrexate, folic acid supplements are sometimes prescribed with methotrexate in people with rheumatoid arthritis or to prevent methotrexate side effects like mouth sores.

How to avoid folic acid side effects

Folic acid is generally taken without problems, but it pays to take a few steps to be extra safe.

1. Follow the directions

Don’t make up your own dosage to take. Take what the bottle, package insert, or healthcare provider tells you to take. It may seem smart to take “extra”—how could it hurt, right?—but it’s not. At best, the extra folic acid won’t do much good. At worst, it may cause long-term problems.

2. Don’t exceed the recommended daily allowances when taking vitamin supplements

Some people take folic acid supplements in combination with other vitamins and minerals including B-complex vitamins. Before taking these combination vitamins, research the recommended dietary allowances (RDA) of all the vitamins and minerals in the products and follow those guidelines.

3. Don’t take prescription doses of folic acid using multivitamins

A healthcare provider may suggest taking more than 400 mcg per day or prescribe a higher amount of folic acid. If that happens, don’t try to increase your folic acid intake by taking multivitamins or B-complex vitamins. Taking too many of those other vitamins or minerals could cause side effects.

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4. Tell the prescriber about all medical conditions and medications

If a healthcare professional prescribes folic acid supplements, make sure to tell the prescriber about any prescription drugs, over-the-counter medications, supplements, and pre-existing medical conditions , particularly:

  • Seizure disorders
  • Anemia
  • Alcoholism
  • Liver disease
  • Kidney problems

5. Consider filling a prescription

If a healthcare professional prescribes folic acid, consider filling that prescription rather than buying over-the-counter folic acid. Prescription supplements meet higher standards of quality and reliability. For all practical purposes, you don’t know what is contained in an over-the-counter supplement. If prescription folic acid is too pricey, use a SingleCare discount card or ask the prescriber to identify the most reliable over-the-counter folic acid supplements.

6. Take folic acid with food

To avoid digestive system issues, take each folic acid supplement during or after a meal.

7. Avoid drinking alcohol

Alcohol reduces the body’s ability to absorb folic acid, so it doesn’t make much sense to drink and take folic acid supplements. If taking prescription folic acid, take a break from drinking until treatment is over.

How to treat side effects of folic acid

Side effects of folic acid are rare, except in cases of people taking high doses. Unless high doses have been prescribed, don’t take more than the recommended daily allowance.


Nausea can be handled by rest. An antihistamine or other anti-nausea drug could help. If nausea is accompanied by vomiting, drink fluids in small amounts to prevent dehydration.


Eat small meals, exercise, and drink more fluids if experiencing bloating, abdominal distention, or excess gas when using folic acid supplements. If taking over-the-counter folic acid, consider switching to a different product.

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Allergic reactions

If an allergic reaction is experienced while taking prescription or over-the-counter folic acid dietary supplements, stop taking the supplement and get medical attention. Symptoms include:

  • Skin redness
  • Skin rash
  • Hives
  • Itching
  • Shortness of breath
  • Swollen face, neck, mouth, or throat



Why do I feel sick after taking folic acid? ›

But some of these ingredients, such as iron and folic acid can be the cause of stomach irritation— especially if the tablet contains too much iron, or is too large.

What problems do folic acid cause? ›

Low levels of folic acid can cause megaloblastic anemia. With this condition, red blood cells are larger than normal. There are fewer of these cells. They are also oval-shaped, not round.

What should you not take with folic acid? ›

Do not take your folic acid within 2 hours before or after taking indigestion remedies (antacids containing aluminium or magnesium), as they may stop the folic acid being properly absorbed.

How long after taking folic acid will I feel better? ›

Folic acid usually starts to work in a few hours. But if you're taking it for folate deficiency anaemia, it may be a few weeks before you start to feel better. It's important to keep taking your folic acid for as long as it's recommended.

Does your body get rid of excess folic acid? ›

Excess folic acid is excreted in urine. A high folate intake can mask vitamin B-12 deficiency until its neurological effects become irreversible. This can typically be remedied by taking a supplement containing 100 percent of the daily value of both folic acid and vitamin B-12.

Does folic acid make one dizzy? ›

Potential Side Effects

Call 911 or go to your nearest emergency room if you develop rash or hives, shortness of breath, wheezing, rapid heartbeat, dizziness, or the swelling of the face, throat, or tongue after taking a folic acid supplement.

Can folic acid 5mg make you feel sick? ›

Folic acid supplements are unlikely to cause any side-effects. The 5 mg tablets may, on rare occasions, cause mild upset stomach (loss of appetite, nausea, and a bloated feeling). If you experience any symptoms which you think may be due to the tablets, speak with your doctor or pharmacist for advice.

Can folic acid make you feel tired? ›

It can cause symptoms like weakness, fatigue, difficulty concentrating, and shortness of breath ( 14 , 15 ). If you take folic acid supplements and recognize any of these symptoms, consider getting your B12 levels checked. High intakes of folic acid may mask a vitamin B12 deficiency.

Does folic acid affect the brain? ›

Some of the important functions folate aides in are the creation of DNA and RNA, formation of neurotransmitters, and the formation of the nervous system during pregnancy. Folate is also known to help with depression, mental fatigue, and irritability because it can be quickly broken down and supply the body with energy.

What happens if you have too much folic acid? ›

What happens if I take too much folic acid? Taking doses of folic acid higher than 1mg can mask the symptoms of vitamin B12 deficiency, which can eventually damage the nervous system if it's not spotted and treated.

What is the best way to take folic acid? ›

You can take folic acid with or without food. Swallow the tablets whole with a drink of water. If you're taking folic acid as a liquid, it will come with a plastic syringe or spoon to help you measure out the right dose. If you do not have one, ask your pharmacist for one.

What fruit is good for folic acid? ›

Besides being delicious and full of flavor, citrus fruits like oranges, grapefruit, lemons, and limes are rich in folate. Just one large orange contains 55 mcg of folate, or about 14% of the DV ( 17 ).

Does vitamin D interact with folic acid? ›

No interactions were found between folic acid and Vitamin D3.

How does folic acid make you feel? ›

When taken by mouth: It is likely safe for most people to take folic acid in doses of no more than 1 mg daily. Doses higher than 1 mg daily may be unsafe. These doses might cause stomach upset, nausea, diarrhea, irritability, confusion, behavior changes, skin reactions, seizures, and other side effects.

What are signs of lack of B12? ›

Symptoms of vitamin B12 deficiency
  • a pale yellow tinge to your skin.
  • a sore and red tongue (glossitis)
  • mouth ulcers.
  • pins and needles (paraesthesia)
  • changes in the way that you walk and move around.
  • disturbed vision.
  • irritability.
  • depression.

What happens if you forget to take folic acid one day? ›

When taking folic acid, follow your doctor's directions carefully, and be sure to read the package label. If you miss a scheduled dose, take it as soon as you remember. But if it's almost time for the next dose, just skip the missed one. Then return to your normal dosing schedule.

What is the difference between folate and folic acid? ›

The terms “folic acid” and “folate” often are used interchangeably. However, folate is a general term used to describe the many different forms of vitamin B9: folic acid, dihydrofolate (DHF), tetrahydrofolate (THF), 5, 10-methylenetetrahydrofolate (5, 10-MTHF), and 5-methyltetrahydrofolate (5-MTHF) 1.

Does folic acid cause neurological symptoms? ›

folic acid may also cause neurological complications. In fact, aggravation of the neurological complications of patients with pernicious anemia treated with folic acid has been reported and suggests that the administration of this vitamin may be harmful to the nervous system under some circumstances.

Can folic acid give you headaches? ›

A significant correlation was observed between dietary folate consumption and migraine frequency. The conclusion of this study was that folate intake may influence migraine frequency in female sufferers with migraine with aura.

Does nausea from folic acid go away? ›

If you're taking it because you're pregnant, you probably will not feel any different, but that does not mean it's not working. You're unlikely to get side effects with folic acid, but some people feel sick, lose their appetite, get wind or feel bloated. These side effects are usually mild and do not last long.

Does folic acid affect sleep? ›

Folic acid is generally regarded as safe. Side effects are rare. High doses of folic acid can cause nausea, bloating, gas, and insomnia.

Is folic acid taken morning or night? ›

There is no need to take the supplement at a specific time of day or with a meal. However, developing a habit, such as taking a prenatal vitamin every morning with breakfast, may make it easier to remember to take folic acid.

Can folic acid cause forgetfulness? ›

A lack of folic acid has been connected to a risk for memory loss or dementia later in life. If your loved one is facing hospice in Alameda County and elsewhere or suffers from dementia, you may be concerned that low folic acid intake may have been to blame.

Does folic acid heal nerves? ›

Folic acid shows great potential in repairing nervous system injury because of its neurotrophic effects (Balashova et al., 2018). Folic acid, a derivative of water-soluble vitamins, plays a key role in the growth, differentiation and regeneration of the central nervous system (Iskandar et al., 2004, 2010).

Can folic acid cause depression? ›

Both low folate and low vitamin B12 status have been found in studies of depressive patients, and an association between depression and low levels of the two vitamins is found in studies of the general population.

What level of folic acid is toxic? ›

The tolerable upper intake level (UL) for folic acid was established at 1,000 mcg/day (one-fifth of the LOAEL) to prevent individuals from taking so much folic acid that they reach the LOAEL risk level of 5,000 mcg/day 15.

How much folic acid is unsafe? ›

It's unlikely that women will be hurt from getting too much folic acid. We don't know of an amount that is dangerous. Yet, for most women, consuming more than 1,000 mcg of folic acid daily is of no benefit. Unless their doctor advises them to take more, most women should limit the amount they take to 1,000 mcg a day.

What are 3 benefits of folic acid? ›

Folic acid supplements are used for:
  • Preventing neural tube defects in babies.
  • Preventing and treating anemia.
  • Preventing side effects from taking methotrexate.
  • Treating a folate deficiency.
22 Mar 2022

What is the most important time for folic acid supplementation? ›

Key Points
  • Taking folic acid before and during early pregnancy can help prevent neural tube defects in your baby.
  • Before pregnancy, take a vitamin supplement that has 400 micrograms of folic acid in it every day.
  • During pregnancy, take a prenatal vitamin that has 600 micrograms of folic acid in it every day.

Can I drink milk before taking folic acid? ›

Yes. There used to be a recommendation of waiting two hours before taking a multivitamin after consuming dairy product to promote better absorption of iron in the supplement, but there is no clear evidence that calcium interferes with iron absorption.

Are cucumbers high in folic acid? ›

vitamin C: 4.5 mg. folate: 19.9 mcg. beta carotene: 44 mcg.

Do apples have folic? ›

Use the folate amount (micrograms DFE) to compare against the Recommended Dietary Allowances (RDA) for folate.
Choose your food:
FoodServing SizeFolate Amount (micrograms DFE*)
Apple (with skin)1, medium5
Banana1, medium20
Blueberries, fresh½ cup5
Cantaloupe¼, medium40
43 more rows
8 Jun 2017

Is milk high in folic acid? ›

Besides being a great source of calcium, protein and vitamin D, a glass of milk is also a good way to get more folic acid into your diet.

Can you take vitamin D B12 and folic acid together? ›

No interactions were found between folic acid and Vitamin B12. However, this does not necessarily mean no interactions exist. Always consult your healthcare provider.

Can I take multivitamins while taking folic acid? ›

It is recommended that folic acid be taken in a multivitamin including 2.6 ug/day of vitamin B12 to mitigate even theoretical concerns.

Can I have B12 and folic acid together? ›

Taking folic acid at high doses can hide a vitamin B12 deficiency. So these vitamins are often taken together.

Can folic acid make you dizzy? ›

If you have a folic acid deficiency, you might not know it at first. The signs can come gradually and mimic other common symptoms such as feeling tired, irritable or dizzy.

Can folic acid make you breathless? ›

It can cause symptoms like weakness, fatigue, difficulty concentrating, and shortness of breath ( 14 , 15 ). If you take folic acid supplements and recognize any of these symptoms, consider getting your B12 levels checked.


1. Does folic acid have side effects? How long should you take folic acid?
(yes OR no)
2. Avoid Folic Acid and Take Folate (as methylfolate) – Folic Acid vs. Folate – Dr.Berg
(Dr. Eric Berg DC)
3. Taking Folic Acid Can Prevent Certain Birth Defects
(NJ Spotlight News)
4. Ask a doctor: folic acid supplements
(WKMG News 6 ClickOrlando)
5. Folate Deficiency, Causes (ex. medications), Pathogenesis, Symptoms, Diagnosis and Treatment
(JJ Medicine)
6. Why You Should Take Folic Acid BEFORE Pregnancy
(Nucleus Medical Media)
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