My cat with bladder issues is vomiting green and won't eat Rx food.

You can certainly try this, but if it doesn't entice him to eat I would start to wonder if he really has an upset stomach and he doesn't want to eat because he's truly nauseous. If he doesn't want to eat the mix of his old food and the new food tonight or in the morning I would consider scheduling a recheck for him to see if something else is wrong. Certainly the resolution of his urinary problems depends on his eating the s/o food, so he needs to get back on that as quickly as possible as well.

When was Marshmallow put on Urinary SO? If he was just put on the food and he wasn't gradually transitioned to it they can get an upset stomach from it. If this is the case I would call your veterinarian for a bland diet and potentially an antacid to help settle his stomach then do a gradual transition to the new food. If Marshmallow has been on the food for some time, it is less likely the food and more likely something else is going on with Marshmallow. If this is the case I would recommend a visit with your veterinarian and potentially some X-rays making sure there is not foreign body obstruction and some blood work looking for pancreatitis. Your veterinarian can also give him medication to help stop the vomiting and settle his stomach. If you are uncomfortable with the food that they put him on there are other prescription diets for cats you can always ask your veterinarian which other ones they recommend. Thank you for using Petco Pet Education Center, formerly Petcoach.

Hill's non-prescription food is safe, and it's a highly recommend food by vets. There is absolutely no scientific research saying it isn't safe, everything you are reading is anecdotal with no evidence to back it up. It's important that your cat stays on a urinary diet to keep him from getting stones again, so I'd recommend giving him Royal Canin cat urinary SO. It's a high quality food, and he may like eating it. I would have him checked out by a vet about this weight loss, however. In old cats, the weight loss could be due to a medical illness, such as hyperthyroidism, kidney disease, diabetes, or even cancer. He could also have teeth problems making it painful for him to eat. He could not be feeling well from those, causing him to not eat, so it may not be the food, it could be an illness. I recommend having a physical exam, geriatric blood panel, and urinalysis to check his teeth and to see how his organs are functioning to determine if there is a medical cause behind this weight loss and anorexia. Should one be found, the vet can treat him for it. I would have him seen by a vet today or tomorrow.

That is a good food. Often cats eat too fast and vomit up semi digested food. I recommend switching to C/D canned or giving both canned and dry. Often with canned food there will be less vomiting and the food will still be effective to prevent crystals. Thanks for using Petco Pet Education Center, formerly Petcoach to help you care for Spike.

Surgery may be the next option if he won't eat the prescription diet. Discuss other diets, both canned and dry, with your veterinarian first. It may take several weeks to months to fully dissolve any stones or crystals. Try to get him to drink as much water as possible to dilute his urine.

I would just continue to watch Dexter for a day or two. It is possible that the sudden switch in food (even if back to the prescription diet) has caused some irritation that should settle down quickly. If the vomiting lasts longer than 24 hours, or if Dexter has no interest in eating the z/d or seems lethargic, it would be best to have him checked out by your vet.

Thank you for submitting your question regarding Speedy. If his veterinarian has recommended a prescription diet, then he should stay on one. Royal Canin Veterinary Diets Urinary SO, Hills Veterinary Diet C/D or Purina ProPlan Veterinary Diets U/R are all great choices to help prevent crystals in his urine. I hope this information helps!