At the time of appearing for NEET, you will need your:

Admit Card

Valid Id Proof

3 Passport size photographs

Self declaration form

PWD certificate if applicable

Once you appear for NEET and qualify, you appear for Counselling. And if you secure a seat, during document verification you should submit the following documents:

NEET Admit card

NEET score card

10th marks sheet

12th marks sheet

PWD certificate if applicable

Category Certificate if applicable

Domicile certificate

So you will  need your 12th marks sheet during document verification and seeking admission in the College. That is important. So what we would suggest you is to wait until the results have been announced and then request for your 12th marks sheet from your College. Most Colleges do give Original marks sheet with an undertaking. Without your 12th marks sheet, your document verification might be incomplete and you cannot proceed further. But your results wont be stopped. You just cant take admission in a Medical College.