Diabetes mellitus
Insufficient insulin or insulin resistance leading to high blood sugar. Common in older overweight cats and middle-aged dogs. Highly manageable with twice-daily insulin.
Diabetes in pets is similar to type 1 (dogs) and sometimes type 2 (cats) diabetes in humans. The body can't move sugar into cells, so blood sugar rises and the body switches to burning fat for energy, producing ketones in severe cases.
Signs: increased thirst, increased urination, increased appetite combined with weight loss, lethargy, sometimes cataracts in dogs (rapid-onset blindness). Diagnosis is straightforward — a single blood glucose and urine sample is usually conclusive.
Treatment is twice-daily insulin injections (most pets tolerate this very well) plus a controlled diet, ideally fed at the same times each day. Most owners are anxious before starting and surprised at how routine it becomes after a week or two.
Cats sometimes achieve remission with early aggressive treatment, weight loss, and a low-carb diet — meaning they no longer need insulin. Dogs essentially always need lifelong insulin.
With consistent management, most diabetic pets live a normal lifespan and quality of life. Diabetic ketoacidosis (DKA) is an emergency where the body has decompensated — vomiting, severe lethargy, dehydration — and needs hospitalisation.