Dear candidate it's never too late to start any exam preparation. But problem is there if your Biology is weak, if you really wish to crack NEET exam you need to possess profound knowledge on the subject and have the proper grip of biology. Though Chemistry, Physics will also be the subjects which you have to face during the entrance but try to be strong in Bio, if you are your dedicated will definitely lead you to success. As an unreserved candidate you need to score more than 600 to get government MBBS college. So you can understand the hard work you need to do,

Good luck!!