If you use OD at the end of sentence do need two periods O.D..?

No, you only need one period at the end of a sentence, even if it ends with an abbreviation like "O.D."

Here's how it should look:

* Correct: The doctor prescribed the medication O.D.

* Incorrect: The doctor prescribed the medication O.D..

The period after "O.D." serves as the end-of-sentence punctuation.