Diabetes mellitus strikes 1 in 400 cats an a similar number of dogs, though recent veterinary studies note that it is becoming more common lately in cats. Symptoms in dogs and cats are similar to those in humans. Generally, most dogs and about 5-20% of cats experience type-1 (insulin-dependent) diabetes, rather than the type-2 that's now becoming common in obese humans. The other 80-95% of cats experience type-2 diabetes.. The condition is definitely treatable, and need not shorten the animal's life span or life quality. In type-2 cats, prompt effective treatment can even lead to diabetic remission, in which the cat no longer needs injected insulin. Untreated, the condition leads to blindness in dogs, increasingly weak legs in cats, and eventually malnutrition, ketoacidosis and/or dehydration, and death.