The most common form of diabetes in dogs is diabetes mellitus or sugar diabetes, which occurs due to either a lack of production of insulin (the hormone that regulates glucose levels) by the dog's pancreas, or because of an insensitivity to insulin. When blood glucose levels are too high, it's excreted in the urine, causing an excessive loss of water in the process. The dog then compensates by drinking more. Sometimes dogs with diabetes will lose weight as they burn through stores of fat and muscle trying to make glucose. Other symptoms can include cataracts, increased appetite, exercise intolerance and recurrent infections. What's more, when fat is burned to make glucose, compounds called ketones are also produced, which, if allowed to build up in the bloodstream cause ketoacidosis, which makes the dog very unwell and requires intensive treatment.