prenatal vitamins are available both over the counter in retail stores as well as by prescription from medical professionals. although prescription vitamins are often covered by insurance, the relative potency of prescription-grade products are typically not significantly different from those available through retail. differences in prescription versus retail vitamins do however exist in consistency and quality level, as well as the relative bioavailability of some specific ingredients. for example, many prescription prenatal vitamins will contain a more bioavailable form of folate; 5-methyltetrahydrofolate (5-mthf). doses of folic acid over 1mg are prescription only. the amount of non-prescription prenatal vitamins needed to achieve this dose may have too much vitamin a and lead to fetal toxicity.