Hey Dimple!

You can give the MCAT test, whilst doing the course, however, for applying for MD programs, other than the course you are currently enrolled in, in USA you will have to produce your undergraduate degree. So, make sure to check the terms and conditions of the program you are currently enrolled in (check whether you can switch after completing your UG or do you have to stick through during the entire duration of the program; if at all you plan to change or switch). 

For more information regarding the MCAT test, you are advised to visit the following links:

https://studyabroad.careers360.com/articles/mcat

https://studyabroad.careers360.com/articles/mcat-syllabus

Hope this helps. All the best!