My Dr. recommended 2mg of folic acid and 400mg of DHA other wise it has no effect and it's not worth taking. My Prenatals only have 228mg of DHA. It's also a good idea to take calcium 1000mg
I take both a prenatal and folic acid, even though my prenatal has folic acid in it. My OB said one can't overdose on folic acid.
Eirlis is correct, you need more than just the folic acid. Go to walmart or another large food chain and you can get a pregnancy vitamin with approx 800MCG (micrograms not milligrams) of folic acid. Dr's reccomend taking approx 2-5 milligrams of folic acid only if you have had a child with a neural tube defect (spina bifida, etc). the 5mg won't hurt you or the baby if you do get pregnant.
I took 3mg during my pregnancy (both of them) and my son's both turned out fine regarding the neural tube defects. it is ok to take a little additional folic acid especially in the first 3 months of pregnancy. Also I'd reccomend Fish Oil (omega 3 fatty acids) they are great for helping the baby's brain to develop during early pregnancy.
You need more than just folic acid. Take a good prenatal vitamin. You can buy them at pharmacies or health food type stores.