- One more question on my cat, Zax, who was diagnosed this week with HCM. I understand the need to increase his Lasix if he goes back into heart failure. But how do I know if his Lasix or Enalapril needs to be decreased? I don't remember the vet covering this. I know Zax's creatinine and BUN will be checked once he's been on the meds for 10 days but am not sure how often it's checked after that. How do I make sure he is not getting too "dry"?