If you will get 2 merits then you will have only one smerit  (sending merit). This means if you will get 10 merits then those merits will make 5 smerits  that you can send to others. But you are asking if your merits will be reduced if you will send merits to others. The short answer is no.

Because as I said before, you get 2 merits that make 1smerit. And the 2 merits that you have received will not go anywhere. They are registered in your profile and the merits that you will send, not be deducted by the merits that have been tagged in your profile.

But yeah, you can not send someone endless merits because if you wanted to send smerits then you must have earned some merits too then you will be able to send merits. The best practice that you should perform in this case is, do not start to do merit farming in thinking that you can now send merits to your other account. Because that will not be tolerated.