Folic acid benefits: what it does, and what it does not

The main proven benefit of folic acid is a lower chance of neural tube defects. These are serious problems with a baby's brain or spine, such as spina bifida. It works best when you start before pregnancy, because the neural tube closes in the first weeks, so the National Health Service says to take 400 micrograms a day, ideally from three months before you try for a baby and through the first 12 weeks of pregnancy.

Outside pregnancy, folic acid is a B vitamin your body uses to make red blood cells and DNA, the material that carries your genetic information. Those jobs are real, but they are not a reason to take extra. This guide separates what the health authorities say it does, what they say it might do, and what nobody has shown.

What folic acid does in the body

Fewer neural tube defects. This is the main one. The National Health Service says taking folic acid in the weeks before and early in pregnancy reduces the chance of your baby having a neural tube defect, such as spina bifida. MedlinePlus says getting enough before and during pregnancy helps prevent this type of birth defect. The World Health Organization (WHO) says current evidence suggests folic acid taken around the time of conception can prevent neural tube defects.

Healthy red blood cells. MedlinePlus lists helping the body form red blood cells, and so helping prevent anaemia, among the jobs of folate. The National Health Service says that a lack of folate can cause the body to make abnormally large red blood cells that cannot work properly, a condition called folate deficiency anaemia.

Normal cell growth. MedlinePlus says folate helps tissues grow and cells work, and that it helps the body make DNA. These jobs do not make folic acid a treatment for tiredness or hormone problems.

Benefits that are possible, but not promised

The National Health Service says folic acid can also help prevent other problems, such as cleft lip and palate or some heart conditions. It does not give a figure, and neural tube defects remain the benefit it names first.

MedlinePlus says that taking higher doses of folic acid before you get pregnant and during the first trimester may lower your chances of miscarriage. We treat this as a possibility, not a reason to raise your own dose. The doses above 1,000 micrograms a day carry cautions, set out below, so any change from the standard 400 micrograms is a conversation with a doctor first.

Why the timing matters more than the dose

The neural tube is the early structure that becomes the brain and spine. A 2020 study of women in Benue State, Nigeria, published in the Pan African Medical Journal, describes the problem plainly. Its authors write that a neural tube defect "occurs when the neural tube fails to close between 21 and 28 days after conception even before the women realize they are pregnant."

That is the reason for the "before you try" advice. By the time a test shows two lines, much of the window has passed. The National Health Service says to start ideally three months before you try for a baby, or as soon as you find out you are pregnant if you did not plan it, and to continue for the first 12 weeks. WHO says all women should take it from the moment they begin trying to conceive until 12 weeks of pregnancy. The National Health Service also says that if you keep taking it for longer than 12 weeks, it will not harm your baby.

Most women are advised to take 400 micrograms a day before conception and during early pregnancy. Some women need a higher dose on prescription. Our preparing to conceive guide explains the timing and who may need more, and a doctor decides your dose.

Folate, folic acid and food

The two words are close but not identical. MedlinePlus says folate is the B vitamin that occurs naturally in food, such as dark green leafy vegetables, dried beans and peas, and citrus fruits and juices. Folic acid is the man-made form, found in supplements and added to fortified foods such as enriched breads, cereals, flours, cornmeals, pastas and rice.

The National Health Service says it is difficult to get the amount you need from food alone in pregnancy, so it recommends a supplement. MedlinePlus says the same for women thinking about becoming pregnant.

The sources we cite name food groups. They do not give folate amounts for Nigerian vegetables or soups, so we do not give a list. The food groups above are the ones the sources name. They also do not say which Nigerian flours or cereals have folic acid added, so read the label on the pack.

Folic acid tablets: what they are used for

The sources we cite describe folic acid tablets in two settings. The first is the pregnancy use above, at 400 micrograms for most women. The second is treatment, after a blood test shows a low folate level. The National Health Service says folic acid tablets are used to restore folate levels and usually need to be taken for 4 months, and that these conditions are diagnosed from symptoms and a blood test. It lists tiredness, pins and needles, a sore red tongue, mouth ulcers and problems with memory among the signs of low folate or low vitamin B12.

The Benue study's authors note that women in Nigeria are routinely given 0.4 milligrams of folic acid at antenatal care. That is the same 400 micrograms. The National Health Service says you can buy folic acid supplements from pharmacies, supermarkets and online, and a doctor can prescribe the higher dose.

Taking it every day: is it safe?

At the usual amount, yes. MedlinePlus says folic acid does not cause harm when used at recommended levels. It says leftover amounts leave the body in the urine, so excess does not build up, and because the body does not store folic acid, a regular supply is needed.

There are two cautions.

Do not go above 1,000 micrograms a day on your own. MedlinePlus says to avoid taking more than 1,000 micrograms a day, except for women with a history of a pregnancy affected by a neural tube defect who are planning a pregnancy. It adds that, although the risk is low, higher levels of folic acid can mask vitamin B12 deficiency, so a deficiency could go unnoticed.

Tell your doctor about certain medicines. The National Health Service says some medicines, including those for epilepsy, can affect how much folate your body absorbs, and it lists epilepsy medicine and HIV medicine among the reasons for a higher prescription dose.

The pages we cite do not give a full list of people who should avoid folic acid, so this guide is not a clearance. If you have a long-term condition or take regular medicine, ask a pharmacist or doctor before you start.

What women in Nigeria know and do

The Benue State study interviewed 586 women aged 15 to 49 at six secondary health facilities in 2016. Fewer than half (48%) knew folic acid as a supplement. About one in four (26%) knew its link to birth defects. 37.7% had used it, and among those who had, roughly one in four had started before pregnancy and about four in ten after the first trimester. The commonest reason women gave for not using it, apart from no reason, was an unpleasant smell (21%).

This is one state, in 2016, at health facilities, so it is not a picture of all Nigeria. In this study, 48% knew folic acid as a supplement, but only about one in four of the women who used it had started before pregnancy.

What folic acid does not do

None of the authorities we read says folic acid makes it easier to get pregnant. They say it reduces the chance of neural tube defects when taken before conception and in early pregnancy. For what else helps before you try, and for the myths around fertility and hormones, see our guide on preparing to conceive. To find your fertile days, use the ovulation calculator. Once you have a positive test, our guide to taking a pregnancy test at home explains how to read it.

Common questions

Sources

• Vitamins, supplements and nutrition in pregnancy, including the 400 microgram and 5mg folic acid doses, National Health Service
• Vitamin B12 or folate deficiency anaemia: symptoms, causes and treatment, National Health Service
• Periconceptional folic acid supplementation to prevent neural tube defects, World Health Organization, 2023
• Folic acid in diet: functions, food sources, side effects and recommended amounts, MedlinePlus, 2025
• Folic acid: neural tube defects and pregnancy, MedlinePlus
• Awareness and use of folic acid among women of childbearing age in Benue State, Nigeria, Pan African Medical Journal, 2020