What happens if you take too many prenatal vitamins?

As a water-soluble vitamin, folic acid is not especially dangerous in the case of an overdose. Any excess is usually just excreted in the urine without causing any problems. However, high doses of folic acid (especially if taken long-term) have been reported to cause some problems, such as: * Digestive problems (such as nausea or gas) * Rash * Problems sleeping (including unusual dreams) * Irritability, excitability, or hyperactivity * Bitter taste in the mouth * Zinc deficiency * Psychotic behavior * Seizures (typically in people who already have a seizure disorder). High doses of folic acid can also "mask" a vitamin B12 deficiency (effectively treating the anemia caused by the deficiency without stopping the nerve damage caused by the deficiency). There is also some concern that high-dose folic acid supplementation may also increase the risk of heart attacks in people with heart disease.

source: http://pregnancy.emedtv.com/folic-acid/folic-acid-overdose.html