Deduction u/s 80d

Dear Collegue,

If any medical insurance policy's period is DEC 17 to NOV 18 and the premium paid amount is Rs.6000 for the said period, then at the time income tax computation (for F.Y. 2017-18) whether we have to take the premium amount proportionatly i;e from Apr 18 to Jan 18 or we can take the total premium amount i;e Rs. 6000 ? which will be rational ?