What are the side effects of parental vitamin if your not pregnant and don't plan to be?

Prenatals?: Did you mean "prenatal vitamins"? If you take prenatals and are not pregnant, there is no serious adverse events. The most common side effect is occasssional constipation and mild nausea due to the iron content in them. Prenatals are a great suppliment but do contain higher iron than others. I recommend prenatals that have a stool softener as well as omega-3.