There is no reason to take prenatal dietary supplements if you are not pregnant and are not trying to get pregnant.

Some people take prenatal supplements because of unproven claims that they give you thicker hair and stronger nails. Other people take them with the idea that more of a nutrient is better. But when your body doesn't need it, taking supplements could put you at risk over time.

Prenatal supplements give the extra vitamins and minerals needed before and as a pregnancy starts. These types of supplements have different amounts and types of vitamins, minerals and other additives such as omega-3 fatty acids. But the main difference between a prenatal vitamin and a multivitamin is the amount of folic acid and the amount of iron.

Having enough folate from food, or folic acid from supplements and fortified food, at the start of a pregnancy lowers the risk of certain birth defects. The amount of folic acid suggested for people who are planning a pregnancy is 400 to 800 micrograms (mcg) a day. The typical amount of folic acid for an adult is 400 mcg a day.

Having enough iron helps the body make the extra blood cells needed during pregnancy. The amount of iron needed in pregnancy is 27 milligrams (mg) a day. For iron, the typical daily amount is 8 mg for males and 18 mg for females.

Taking iron and folic acid at levels higher than the suggested amounts may bump people closer to the upper limit for these nutrients. For folic acid as a supplement, the maximum daily amount is 1,000 mcg a day for adults. The maximum amount for iron, which includes food and supplements, is 45 mg a day for adults.

Going over those limits can raise the risk of health problems. With folic acid, too much might make some symptoms of vitamin B-12 deficiency worse. And with iron, too much can affect zinc levels in the body. Too much iron can make you feel sick to your stomach. Also, it could cause loose stools or stool that is hard to pass.

Most of the time a nutritious, balanced diet makes taking any dietary supplement unnecessary for healthy adults who are not pregnant. Iron and folate are found naturally in many foods. For example, spinach is a good option for iron and folate. Other foods, such as breakfast cereal, are fortified with iron and folic acid.