Whenever you notice a change in your cat, be it behavioral or physical, it's a safe bet that there's an underlying issue that needs to be addressed. Claudia K. writes:
Claudia, cats can sometimes have a sudden onset of leg weakness (usually the hind legs) due to diabetes, a blood clot, epilepsy, or physical injury. Arthritis is also a possibility and some breeds are prone to hip dysplasia.
When you add in the facts that he's losing weight and drinking more than usual, the signs indicate diabetes. Diabetes is easily treatable and Sully can live a long and healthy life with the disease, but he needs to see a veterinarian ASAP.
If Sully's vet diagnoses him with the disease, your first order of business is to make sure he's on a low-carbohydrate diet. We have a post on this very subject here:
Diabetes has become a feline epidemic because of all of the high-carb foods in the marketplace these days. Many of the most popular brands of cat food, especially dry foods, are mostly carbs. Pet food manufacturers are literally getting away with murder by pushing these awful products on an unsuspecting public. The only way we can combat them is to educate ourselves on products that deliver a healthy, species-appropriate diet.
Be careful not to fall into the trap of prescription diets for diabetes. Many veterinarians prescribe them and cats seem to get better, but most of those diets are high-carb as well. Feline diabetes can actually go into remission if the cat is fed a species-appropriate diet.
You also want to make sure that Sully is getting plenty of exercise every day. At the age of five, he should have at least two thirty minute play times daily, during which he gets a vigorous workout. If you're having difficulty transitioning him to new food, it can help to have these play times right before meal times.
We wish you and Sully all the best!