Does giving a cat sub-q fluids create urine in the bladder? My cat's bladder was empty Friday afternoon and he received 150 mL of sub-q fluids. I was supposed to collect a urine sample but he hasn't used the litterbox yet. I'm wondering if the sub-q fluids would create urine in the bladder. My hopes are that it does and that he can hold it for about four more hours so I can take him to the vet so they can get a sample themselves. I don't want to take him back in if he doesn't have urine in his bladder.