Folic acid is a synthetic form of folate, one of the B vitamins. You can normally get enough folate naturally in your diet. However, folic acid supplements are needed in the following situations:

What is folic acid used for?

To treat and prevent folate deficiency anaemia

This type of anaemia can occur as a result of poor nutrition, malabsorption syndromes such as coeliac disease, alcoholism, pregnancy, or taking certain antiepileptic medicines. Your doctor might also ask you to take folic acid supplements to prevent aneamia if you have a condition where the body breaks down red blood cells too quickly (haemolytic anaemias, eg sickle cell aneamia), or if you're having kidney dialysis.

As a dietary supplement for pregnant women and women planning a pregnancy

Folic acid supplements help prevent neural tube birth defects such as spina bifida and other congenital malformations such as cleft lip or palate in the developing baby.

To help reduce side effects associated with taking methotrexate for severe arthritis, Crohn's disease or psoriasis.

How does folic acid work?

Folic acid is an essential ingredient for making the genetic material of cells (DNA), and so is vital for growth and development. Folic acid is particularly important for maintaining a healthy nervous system and in the formation of red blood cells, which carry oxygen around the body.

Where there's deficiency of folic acid this causes a drop in the numbers of red blood cells in the blood, since folic acid is essential for their production. A course of folic acid supplements corrects the deficiency and allows red blood cell production to increase.

In pregnancy, folic acid is essential for the development of the baby's spiral cord and nervous system. Since this is one of the first things to develop in the baby, it's important that women take a daily supplement of folic acid both while trying to conceive and during the first 12 weeks of the pregnancy. It's difficult to get enough folic acid to prevent neural tube defects just from your diet. 

Can i take folic acid if i'm breastfeeding?

Yes this is fine - folic acid passes into breast milk but it won't have any harmful effects on a nursing infant.

Does folic acid have side effects?

Not really. On rare occasions some people find that it gives them an upset stomach.

If you take more than the recommended amount of folic acid by accident it shouldn't cause any problems, because it is a water-soluble vitamin so your body will just naturally excrete any it doesn't need.

If you regularly take more than 1g folic acid daily this could mask a vitamin B12 deficiency, so you shouldn't do this unless it's prescribed by your doctor.