How much is too much

At what point does throwing up from morning sickness become dangerous and require medical attention? And do you just go to the ER? Looking for nurses or people who have actually needed medical attention to answer. I'm so sick & don't want to be dramatic, but also don't want to be stubborn and put my baby in danger.

*edited. I haven't been able to keep water down but it's only been 4 1/2 hours