I received prenatal vitamins from the hospital that do not have a Hechsher. Can I use them?
You would first have have to see if there is a Kosher version of the ones the hospital gave you.
If none are available -which is unlikely – and your doctor requires you to take them, then, if the medicine is tasteless and non-chewable you may take it. If the medicine is chewable and has a taste, you should crush up the pill into a powder and put it in liquid (so it becomes Batul).
If that is not possible, you should wrap the pill in a tissue and it should be consumed that way.
See S”A Y”D 155:3, Pri Chodesh OC 442 and Shut Tzit Eliezer 6:16.