[Ellie May]

I'd switch to the old and see what you get. If the excessive thirst continues, then definitely vet time.

You can measure water intake to see how much he is over drinking. If you are feeding dry food alone, then he should drink about 1oz/pound daily (give or take).

If the food switch works, then you'll have to go to a different brand that has a food that doesn't cause the thirst. For whatever reason switching back doesn't work, his bladder, kidneys, and metabolic state need to be assessed asap. I would make sure he has free access to water during this time until speaking to the vet because on the off chance (highly unlikely) this is diabetes insipidus, limiting water intake is extremely dangerous.