How much folic acid?
Taking folic acid under medical supervision
Too much folic acid?
When to start folic acid
The minimum, routine, recommended daily intake of folic acid for women before conception, and during the first 3 months of pregnancy, is 400 micrograms (written as 400 ug, or 0.4mg). While it is possible to obtain this level through eating plentiful amounts of foods rich in folic acid every day, it is more likely to be consistently achieved if the woman takes a daily folic acid supplement.
The recommended, routine dosages for folic acid supplements can vary slightly from country to country. In Australia, the dose is generally 400 to 500 ug (or 0.4 mg to 0.5mg). In the USA, the dosages are 400 ug (or 0.4 mg). Various European countries will recommend supplementing with anything from 360ug (or 0.36 mg) to 800ug (or 0.8 mg). Check the recommended dosage with your caregiver.
NOTE: Be aware of the different ways folic acid dosages can be written. The term 'ug' is short for 'micrograms' and the term 'mg' is short for 'milligrams'. Therefore, 1000 micrograms = 1 milligram, 400 micrograms = 0.4 milligrams, 5,000 micrograms = 5 milligrams. This is important, because some women may be advised to have higher doses of folic acid, depending on their circumstances, and dosages over 1,000 micrograms (or 1 milligram) need to be taken under medical supervision.
Taking folic acid under medical supervision. Most women will only need up to 400 to 500 ug (or 0.4 to 0.5mg) of folic acid supplements a day. However, a few women may be advised to take a higher daily dose of 5,000 ug (or 5mg). This is generally the case for women who have had a previous child with a neural tube defect, or who have a close relative that has had a baby with a neural tube defect.
Doses of folic acid this high should only be taken under medical supervision. A blood test to rule out vitamin B12 deficiency should ideally be performed before you start to take higher, daily doses of folic acid. The reasons for this are discussed below in 'Too much folic acid.'
If you think you may need more, seek the advice of your caregiver or
genetic counsellor.
NOTE: Folic acid has the potential to reduce the effectiveness of medications used to control seizures in people with
epilepsy, possibly causing seizures. If you take anti-epileptic medications you should only supplement with folic acid under medical supervision. Consult with your doctor, a neurologist or a
genetic counsellor.
Too much folic acid? While adequate amounts of folic acid are regarded as good for your health. Too much folic acid is not, and it is possible to have too much folic acid. The upper limit for folic acid intake on a daily basis is 1000ug (or 1 mg). This is especially the case if taken for more than a few months.
While most people can tolerate abnormally high daily doses of folic acid, if a person has a vitamin B12 deficiency while taking high levels of folic acid, it is possible (but rare) to develop irreversible nerve damage. Vitamin B12 deficiency is in itself a rare condition. It is usually associated with the bowel's inability to absorb vitamin B12 from foods efficiently, but can occasionally be present in people who do not eat animal products (such as vegetarians or
vegans). Other people at risk or vitamin B12 deficiency are the elderly and people with a condition called 'pernicious anaemia'.
It is believed that if women only routinely supplement with up to 400 to 500 ug (or 0.4 to 0.5 mg) of folic acid a day, as well as eat a plentiful amount of foods naturally rich in folic acid rich and/or fortified with folic acid, are unlikely to exceed an intake of 1000 ug a day. (This is why it is important not to take larger doses of folic acid unless prescribed by a doctor.) Women who are advised to take the higher doses of folic acid (4 to 5 mg) by their caregiver should ideally have a blood test to check for vitamin B12 deficiency before they start their folic acid supplements.
If you are taking a multivitamin
READ THE LABELS. Many brands have less folic acid than the recommended amount (for example 200ug) and others have too much (such as 800ug). Taking '2 tablets' to try and take the correct amount of folic acid may mean you end up taking too much of another type of vitamin that may be harmful to your baby during pregnancy (for example
vitamin A.) Also, don't think that specialised brands that say "for women' or 'for pregnancy' are necessarily better than an average multivitamin (it is usually just a way of making them more expensive!)
When to start folic acid. Ideally, folic acid should be taken for at least 2 months before conception, and up until about 12 weeks of the pregnancy. In reality though, this is not always possible, and as up to 50% of pregnancies are unplanned. Therefore, many women do not have the opportunity to obtain the full benefits of folic acid supplements. Bearing this in mind, it is reasonable to suggest that:
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Supplementing with folic acid tablets for at least one month before conception is considered adequate and will still provide the maximum benefits. |
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If you think you may have had unprotected sex, and could be pregnant (before you miss your first period), then starting supplements before your next period is due, will still be of great help. |
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For women who find out they are pregnant early (or just around the time the first menstrual period is missed, until about 6 weeks of pregnancy), folic acid supplements can still be of benefit, but the earlier the better. |
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Folic acid supplements taken after 6 weeks of pregnancy may be helpful, but probably not as effective. |
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Supplementing with folic acid after 12 weeks of pregnancy is not of any real benefit. |
Folic acid supplements can usually be purchased from a chemist or pharmacy over the counter, without a prescription. Check with the pharmacist or your caregiver that you are taking the correct dosage.
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