Should I defer my midterm MATH 156?

I'm in MATH 156 and my midterm is tomorrow. I have been sick all week and haven't been able to study, I feel okay now and could probably physically write the midterm. Since I haven't had time to study I wanna defer the exam but then the weight would be shifted to my final, making it worth 80% of my grade. My midterm and final normally is 30/50. Should I just try and write the midterm or defer it? How hard is the midterm and finals normally???