Explain why you need a prescription for some medicines and others you do not?

I think some medicines you need a prescription for because there's a Pacific amount of medicine that you need to take but for some medicines like over the counter medicines you won't need a prescription for such as ibuprofen because on the bottle it tells you how many to take. (BTW this is my awnser but I'm not sure it's right)

It is false that oils and fats play an essential role in a healthy died and you should eat approximately 12 teaspoons a day. Whereas the first part of this sentence is true, oils and fats are indeed important for our bodies as they give us strength and proteins, the other part is incorrect. 12 teaspoons is way too much for daily intake, you should take up to 6 teaspoons.