Q: What is the legal upper limit for folic acid in supplements?
– Marci in Santa Cruz

A: A level above 800mcg of folic acid is considered a prescription dose, so this is the upper limit for this B vitamin in over-the-counter supplements. Although usually you will find 400mcg in supplements for the general public and 800mcg in supplements for pregnant women, companies can add up to the 800mcg level in any supplement. Folic acid is relatively non-toxic, with levels of up to 10 milligrams given daily for four months with no harmful effects. Doses of 100 times the current recommended level (400mcg) can precipitate convulsions in people with epilepsy. And while large doses of folic acid could mask an underlying vitamin B12 deficiency, this is easily prevented by taking vitamin B12 along with folic acid. On the other hand, there is no reason to take more than 800mcg and no evidence that more is better unless prescribed by your physician for heart disease or possibly cervical cancer. The exception is for women with a previous history of neural tube defects where up to 4 milligrams a day are recommended to prevent future birth defects. -Elizabeth Somer