Diabetes Mellitus is a disease caused by lack of insulin and/or resistance to insulin. It occurs mainly in middle aged or older dogs and cats. The cause is not fully known yet but heredity is likely a large factor in many cases. Obesity also increases the likelihood that your pet will develop diabetes.

Clinical signs include increased thirst and urination, weight loss and increased appetite. Cataracts may occur and rarely we may see rear limb weakness. If the diabetes has gone untreated for some time or if a diabetic animal gets stressed (e.g. from an untreated infection) the animal may become depressed, may not want to eat and may develop vomiting and/or diarrhea; this is called diabetic ketoacidosis.

The diagnosis relies upon blood and urine tests. Extensive blood tests are necessary to help rule out other disorders that may affect prognosis or cause insulin resistance.

Treatment depends on whether the animal is sick or not. If the animal has diabetic ketoacidosis they should be hospitalized. Fluids are given, usually intravenously, and the animal will be started on insulin. Once the animal is eating, not vomiting and brighter, it can be sent home on insulin. If the animal does not have diabetic ketoacidosis, it will be started on insulin at home after the owner is shown how to give injections under the skin and how to handle insulin.  The blood sugar should be checked 2-4 hours after the insulin injection at the clinic for the first day or two to ensure that it is not getting too low. A week after starting insulin, a blood glucose curve will be done; the patient must be hospitalized for the day after getting insulin and being fed at home. The blood glucose involves taking a blood sugar sample every 1-2 hours for throughout the day in order to see how effective the insulin dose is, how long it is lasting and when it reaches its lowest point. If the blood sugar is not getting to the desired range, the insulin dose will be adjusted and the blood glucose curve will be repeated in another week. This continues until the blood glucose gets down to the desired level.  After the curves reach the desired level, the blood glucose will be checked at the time it

 reaches its lowest level, once a week to start, then gradually less frequently. It usually takes about one month of blood glucose curves to the find the desired dose, although some animals will be regulated after only 1 or 2 curves and some will require several curves.

The owner should be aware of the signs of low blood sugar, as one of the main complications of insulin treatment is low blood sugar. These signs include: weakness, lethargy, wobbliness and seizures. The owner can give food, syrup or sugar water unless the animal is seizuring, in which case it is necessary to phone the clinic immediately. If the patient is vomiting or not eating, phone the clinic; usually the full insulin dose will not be given and an exam will be recommended.

Feeding is important with diabetes. For dogs preferably a high fiber diet should be used; this can decrease insulin requirements by causing weight loss and decreased post-eating fluctuations of blood glucose. Half the calories should be fed within ½ an hour of the injection and the rest at suppertime or at the time of the second insulin injection if the animal gets insulin twice daily. *  For cats higher protein, lower carbohydrate diets are usually recommended.

Oral medications don’t work on most diabetic animals. Some cats will respond to these drugs. These drugs can only be tried if the cat is otherwise healthy and not in diabetic ketoacidosis. Side effects include vomiting and liver disease, blood glucose dropping too low or progression of the diabetes if they don’t work. If there is no improvement after one to two months, the cat should be switched to insulin. Occasionally, a cat will have transient diabetes, where eventually it can be weaned off insulin, especially if they are on a low carb diet and reach a healthy weight.

The prognosis is generally good for most diabetics, unless they have other complicating diseases. However, it should be remembered that diabetes is a potentially life threatening disease and can be expensive to treat, especially if complications occur, so the decision of whether to treat or not to treat should not be taken lightly. If the owner elects not to treat, the patient should be euthanized once it loses its appetite, starts vomiting and becomes depressed.

Here is a great video on giving your cat an insulin injection.  The method used is exactly the same for dogs.