Hello, helpful people,

I get the benefit of 'spending hit dice' to replenish HP on a short rest, but what is the penalty, please? What's the effect of losing hit dice? 

Thanks in hopeful advance.

There is none.  You also don't "lose" the Hit Die, either.  It's on cooldown until after your next Long Rest.  You have a set number, based on your level, and divided into different sizes based on what classes you have.

Thanks so much - I'm still stuck in old editions!

The penalty is you do not have them available if you take another short rest.

I would also point out you can only replenish half your hit dice on a long rest so if you are level 8 and use all your hit dice one day. The next day you would only have 4 hit dice available.

Quote from BigChris6662 >>

Hello, helpful people,

I get the benefit of 'spending hit dice' to replenish HP on a short rest, but what is the penalty, please? What's the effect of losing hit dice? 

Thanks in hopeful advance.

 You have a choice, you can keep using the hit dice until you are full HP, but you may waste a hit die. 

Or you can get close to full HP and save the rest of your HD for the next short rest.

Its just resource management.

Thanks again, All!