I currently have a concussion that has hindered my ability to do work or study. I went to the doctor and got it diagnosed (got a medical note and all that). I have a midterm tomorrow, and I emailed my professor yesterday regarding my concussion and asked to make it up sometime the following week as I am in no shape to take the test. However, he has not responded (even after I followed up on email). He also posted on my classes discussion board, so I am not sure what to do.
Professors get a lot of emails every day, and depending on the size of your class, they could be getting even more. I would not after only a day
In any reasonable department, you are fine. You documented your case by emailing him as soon as you knew you needed to reschedule, and have a doctor's note dated yesterday. If you really want to cover your bases, call his office and leave a message.
In the US (at least), it should not be necessary to go to the exam and ask to be excused*. You don't say how bad your concussion was, but I know that the last time I had a bad one, it would not have been safe for me to travel.
Please rest, you have all the documentation and can figure it out after.
As pointed out in the comments, if your professor is truly a nutcase, you may be able to go to your disabilities services department for help.
* Some might wonder if you're healthy enough to do that, why can't you take the exam?