How do I know if I am smart enough to become a doctor/getting through medical school?

With hard work and motivation it is possible. I'd suggest you take some honors/ap science courses before you graduate. Science courses in college are hard and most bio/pre-med majors end up changing to an easier major. You could also try pursuing a medical career that doesn't involve medical school like a physicians assistant (have to go to PA school) or nursing/nurse practitioner. If you set your mind to it its not impossible.

The issue is probably not so much whether you are smart enough, but whether you are willing to work hard enough and are able to approach your work with the right attitude: seeing failure and ignorance as necessary steps toward success and knowledge, and not stopping when you encounter difficulty, but rather working through it to the other side. What the average person tends to do is give up fairly quickly upon encountering something that is hard for them, often at least in part because they focus on whether or not they are "smart" rather than on the skills that it takes to get past those barriers. (In fact, I once heard one student tell another student in a condescending tone, "You have to understand. You're not smart. You just *work hard*!" as if that were an insult.) But in any case, if you want to be a doctor, you are first going to go to college and earn a bachelor's degree in any subject you like, while also taking the set of classes commonly referred to as "pre-med" because medical schools require students to have taken and passed them before beginning medical studies. You'll need to do very well in college, and you'll need to do well on the GMAT. All of that means that you can work toward becoming a doctor while also studying something that can help you toward another career. You don't have to make the call right now, or next year, or in the couple of years after that. Study something that interests you, take the pre-med classes, and see whether you can get really good grades. If you can, take the MCAT and apply to med schools. If you discover that it is too hard to get the grades you need, or if you discover that you like whatever it is that you're studying better than you think you'd like medicine, or if you find for some other reason that the path to medical school is not the one for you, you can change directions. If you are accepted to medical school, you are pretty much guaranteed to be smart enough to finish and do a residency. (There's a common joke: what do they call the person with the lowest passing grades in the med school class? They call him or her "Doctor.") You will simply need to be willing and able to continue to work hard and not get yourself tangled up in the idea that if you don't understand something the first time you encounter it, that makes you not "smart." If you're prepared for that, you can enroll in medical school and focus on becoming a doctor. If you're not, then you can do something else. What does your dad think?