Lifedrinker and Warlock

the way i read it is that you dont have to expend a hit dice and regain hps ?

Once per turn when you hit a creature with your pact weapon, you can deal an extra 1d6 Necrotic, Psychic, or Radiant damage (your choice) to the creature, and you can expend one of your Hit Point Dice to roll it and regain a number of Hit Points equal to the roll plus your Constitution modifier (minimum of 1 Hit Point).

Yes, the additional damage and the healing are two distinct options. You can use one, both, or neither.

using the hit dice nevers seems an ideal option unless deep doo doo so excellent thank you both

Quote from ueauvan >>

using the hit dice nevers seems an ideal option unless deep doo doo so excellent thank you both

 
Eh; under 2024 you restore all your Hit Die on a Long Rest, so you’re not putting yourself in a hole and you’re getting the same net effect from using a given number of HD via Lifedrinker as you would during a Short Rest. Unless you’ve got another feature that runs off them, there’s little reason not to once you’re down enough not to overflow.