There are certain criteria to fulfil to appear for NEET exam. You should be 17 years atleast by December 31st of the year of admission. You should have completed your 12th with Physics, Chemistry and Biology as your core subjects. You should have secured a minimum aggregate of 50% in Physics, Chemistry and Biology. It is 50% for General Category, 45% for PWD and 40% for OBC,SC,ST. You can study Biology as an additional subject and still be qualified for NEET. Now there is no upper age limit and no cap on the no.of attempts at NEET.