Did/Does My Dog In Kidney Failure Need Fluids?

Hi all, I took my 10 year old male short hair deer head Chihuahua not neutered weighing 7.8 pounds to the vet today and his bloodwork came back indicating he is in kidney failure. Per my vet’s advice, we will be taking him back in the morning for an Addison’s test, but his electrolytes are normal. Should he have received IV fluids? Should I take him now to a Vet hospital? He is eating drinking and going to the bathroom normally other than one day this past week where he refused to drink. His BUN is >130.