Folic acid

1. About folic acid

Folic acid is the man-made version of the vitamin folate (also known as vitamin B9).

Folate helps the body make healthy red blood cells and is found in certain foods.

Folic acid is used to:

Folic acid is available on prescription and comes as tablets or as a liquid you swallow.

You can also buy lower dose tablets from pharmacies and supermarkets.

Folic acid can also be combined with:

  • ferrous fumarate and ferrous sulphate (to treat iron deficiency anaemia)
  • other vitamins and minerals (as a multivitamin and mineral supplement)

2. Key facts

  • You usually take folic acid once a day, but sometimes you only need to take it once a week.
  • Most adults and children can take folic acid.
  • If you're pregnant or trying for a baby, it's recommended you take folic acid until you're 12 weeks pregnant. It helps your baby grow normally.
  • 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.
  • Folic acid is also called by the brand names Preconceive and Lexpex.

3. Who can and can't take folic acid

Most adults and children can take folic acid.

It's not suitable for everyone.

To make sure it's safe for you, tell your doctor before starting folic acid if you:

  • have had an allergic reaction to folic acid or any other medicine in the past
  • have low vitamin B12 levels (vitamin B12 deficiency anaemia) or pernicious anaemia
  • have cancer (unless you also have folate deficiency anaemia)
  • are having a type of kidney dialysis called haemodialysis 
  • have a stent in your heart

4. How and when to take it

If you or your child have been prescribed folic acid, follow your doctor's instructions about how and when to take it.

If you have bought folic acid from a pharmacy or shop, follow the instructions that come with the packet.

How much will I take?

How much you take depends on why you need folic acid.

Before and during early pregnancy

The usual dose for most women trying to get pregnant and during the first 12 weeks of pregnancy is 400 micrograms, taken once a day.

If there's a higher risk of neural tube defects during your pregnancy, your doctor will recommended a higher dose of 5mg, taken once a day.

Folate deficiency anaemia

To treat anaemia, the usual dose for adults and children over 1 year old is 5mg, taken once a day, for 4 months.

Sometimes the dose may be increased to 15mg a day.

If your child is under 12 months old, the doctor will use your child's weight to work out the right dose.

To prevent anaemia, the usual dose for adults and children over 12 years old is 5mg, taken every 1 to 7 days.

This depends on your age, diet and any other health conditions you may have.

For children less than 12 years old, the doctor will use your child's age or weight to work out the right dose.

If you're taking methotrexate

The usual dose for adults and children is 5mg once a week, on a different day of the week to your methotrexate.

Some people take 1mg to 5mg once a day, apart from the day when they have their methotrexate.

How to take it

You can take folic acid with or without food. Swallow the tablets whole with a drink.

If you're taking folic acid as a liquid, it'll 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. Do not use a kitchen teaspoon as it will not give you the right amount.

Will my dose go up or down?

Usually your dose will stay the same.

Your dose may go up, however, if you're taking folic acid to prevent or treat anaemia and blood tests show it's not working properly.

What if I forget to take it?

Missing 1 or 2 doses probably will not matter. But if you keep forgetting to take your folic acid, or you do not want to take it, speak to your doctor.

If you stop taking your folic acid:

  • in pregnancy - the risk of your baby having neural tube defects may increase
  • for folate deficiency anaemia - your symptoms may get worse or new symptoms may appear
  • to reduce the side effects of methotrexate - you'll be more likely to get side effects from methotrexate

If you forget to take folic acid:

  • once a day - take your missed dose as soon as you remember. If it's nearly time for your next dose, skip the missed dose and just take your next dose as normal. If you remember on the day you take your methotrexate, wait a day and take your missed dose the following day.
  • once a week - take your missed dose as soon as you remember, unless you take methotrexate that day. If you remember on the day you take your methotrexate, wait a day and take your missed dose the following day. After this, go back to taking your weekly dose on your usual day.

Never take 2 doses to make up for a forgotten one.

If you forget doses often, it may help to set an alarm to remind you.

You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

What if I take too much?

Folic acid is generally very safe. Taking too much is unlikely to harm you or your child.

If you're worried, speak to your pharmacist or doctor.

5. Side effects

Like all medicines, folic acid can cause side effects in some people.

But many people have no side effects or only minor ones.

Talk to your pharmacist or doctor if these side effects bother you or do not go away:

  • feeling sick (nausea) - but if you're pregnant, this is more likely to be morning sickness
  • loss of appetite
  • bloating or wind

Serious allergic reaction

In rare cases, folic acid can cause a serious allergic reaction (anaphylaxis).

Contact a doctor straight away if:

  • you get a skin rash that may include itchy, red, swollen, blistered or peeling skin
  • you're wheezing
  • you get tightness in the chest or throat
  • you have trouble breathing or talking
  • your mouth, face, lips, tongue or throat start swelling

These are warning signs of a serious allergic reaction.

A serious allergic reaction is an emergency.

Information:

You can report any suspected side effect to the UK safety scheme.

6. How to cope with side effects

What to do about:

  • feeling sick - take folic acid with, or just after, a meal or snack to ease feelings of sickness. If you're pregnant, it could be morning sickness that's making you feel sick.
  • loss of appetite - eat when you'd usually expect to be hungry. If it helps, eat smaller meals more often than usual. Snack when you're hungry. Have nutritious snacks that are high in calories and protein, such as dried fruit and nuts.
  • bloating or wind - it might help to eat smaller and more frequent meals, eat and drink slowly, and exercise regularly. If the symptoms get worse, contact your doctor straight away.

7. Pregnancy and breastfeeding

Usually, folic acid is safe to take during pregnancy.

If you're pregnant or trying for a baby, it's recommended you take folic acid as soon as you start trying for a baby and during the first 12 weeks of pregnancy. This will help your baby grow normally.

Your doctor may advise you to take a higher dose of folic acid if there's a higher risk of neural tube defects during your pregnancy.

You may have a higher risk if:

  • you have previously had a pregnancy affected by a neural tube defect
  • you or your partner have a neural tube defect
  • you or your partner have a family history of neural tube defects
  • you have diabetes
  • you're very overweight
  • you have sickle cell disease
  • you're taking certain epilepsy medicines

For more information about how folic acid can affect you and your baby during pregnancy, read this leaflet on the best use of medicines in pregnancy (BUMPS) website.

Folic acid and breastfeeding

Folic acid is safe to take while you're breastfeeding. It passes into the milk, but it's not harmful to your baby.

But if your baby is premature or has health problems, check with your doctor first.

Important

Tell your doctor if you're trying to get pregnant, already pregnant or breastfeeding.

8. Cautions with other medicines

There are some medicines that may interfere with how folic acid works.

Folic acid can also affect the way other medicines work.

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

Tell your doctor if you're taking these medicines before you start taking folic acid:

  • methotrexate, a medicine used to treat rheumatoid arthritis, Crohn's disease, psoriasis and some types of cancer
  • phenytoin, fosphenytoin, phenobarbital or primidone, medicines used to treat epilepsy
  • fluorouracil, capecitabine, raltitrexed or tegafur, medicines used to treat some types of cancer
  • antibiotics, medicines used to treat or prevent bacterial infection
  • medicines or alternative remedies that contain zinc (including throat lozenges and cold remedies)
  • sulfasalazine, a medicine used to treat the inflammatory bowel conditions ulcerative colitis and Crohn's disease
  • cholestyramine, a medicine used to reduce cholesterol

Mixing folic acid with herbal remedies or supplements

Talk to your pharmacist or doctor before taking any herbal remedies or supplements together with folic acid.

Some vitamin and mineral supplements may already contain folic acid.

Tell your pharmacist or doctor if you take any supplements or remedies that contain zinc.

Folic acid can stop zinc working as well as it should.

Important

For safety, tell your doctor or pharmacist if you're taking any other medicines, including herbal medicines, vitamins or supplements.

9. Common questions

Page last reviewed: 27/03/2019
Next review due: 27/03/2022