It is vital that careful thought be given to the decision to proceed with treatment. The management of diabetes mellitus requires very close observation and daily medication. In some situations, the owner's lifestyle may not allow for careful treatment. However, if the classic signs of diabetes mellitus are present, and the owners are willing to proceed, then treatment usually is recommended.
The goals of treatment are to lessen the signs due to diabetes mellitus and to avoid complications of the disease. It is important to prevent the serum glucose concentration from dropping below the normal range, as serious consequences can occur when hypoglycemia, or a low concentration of serum glucose concentration, develops. Owners should watch for signs of hypoglycemia, which can vary from subtle behavioral changes, to wobbliness and weakness, to severe generalized seizure activity.
Diet is an important aspect of treatment, especially since many diabetic cats are either obese or severely underweight. It is essential to ensure a regular intake of calories and to prevent the cat from consuming excessive protein and fat. As a general rule, semi-moist foods are avoided. Especially for overweight cats, high fiber diets may be helpful in encouraging weight loss and in controlling fluctuations in the serum glucose concentrations. It may be difficult to get a cat to eat a high fiber diet because these diets are sometimes not particularly palatable; introducing the diet gradually, however, may encourage acceptance of the new food. If a cat refuses to eat a high fiber diet, then other diets should be used. In underweight diabetic cats, high fiber diets are generally avoided until blood sugar levels are controlled with medication and a normal weight is achieved. Frequency of feeding is usually dictated by the cat's normal dietary behavior. Cats that eat all day long are probably best fed small amounts many times per day, while cats that eat voraciously but infrequently may do better with meal feedings.
Since some cats have NIDDM, the use of oral medications to lower blood glucose concentrations can be considered. This is especially true if the owners are unwilling to give insulin, if transient diabetes mellitus is suspected, or if the cat seems excessively sensitive to small doses of insulin. The most common oral drug used to treat diabetes mellitus in cats is glipizide. Adverse reactions can include gastrointestinal upset, hypoglycemia, and liver damage. Despite some successes, most permanently diabetic cats cannot be controlled by oral glipizide alone. Other oral medications prescribed for diabetic cats include vanadium and chromium picolinate.
The primary medication used to treat permanent diabetes mellitus in cats is insulin. There are many different types and sources of insulin, but in general, the recombinant human forms of insulin are used most commonly. Production of these types of insulin is unlikely to be discontinued because they are the main types of insulin used to treat human diabetics, although availability of other insulin types has been limited in recent years by discontinuation of their production by manufacturers. The Lente and Ultralente types of recombinant human insulin are used most commonly in diabetic cats. Although some cats do well with once-daily injections of ultralente insulin, most cats eventually require twice-daily administration. Virtually all cats on lente insulin require twice-daily injections.
At-home monitoring requires careful observation for the signs associated with diabetes mellitus. Measurement of urine glucose concentrations and ketones with strips designed for their detection may aid in treatment decisions, but most veterinarians no longer rely heavily on such readings for changes in treatment recommendations. If the signs of increased thirst, urination, appetite, and weight loss are improving, then the treatment is probably appropriate. If those signs are persisting or getting worse, adjustments to the treatment protocol may be needed.
Measurement of serum glucose concentrations over several hours -- ideally 24 hours -- is probably the best way to assess diabetic control. Such glucose curves may be done on an abbreviated basis, as many hospitals are not open overnight. Nevertheless, the ideal method is to measure the glucose level every few hours over 24 hours in a hospital where 24-hour care is available. The measurement substances called fructosamine and glycosylated hemoglobin have recently become more common in veterinary medicine. However, it can be difficult to make specific treatment recommendations based on these readings alone. The measurement of fructosamine can be very helpful in separating stress-induced changes in the blood sugar level from true diabetes mellitus. In cats with well-controlled signs that are extremely distressed by being in the veterinary hospital, the measurement of a single fructosamine level on an outpatient basis may be used in lieu of hospitalization for a full glucose curve. If it is normal, control may be adequate. If the fructosamine level is elevated, then a glucose curve will need to be done to determine what adjustments might be helpful.
As with most illnesses, follow-up recommendations for diabetic cats depend on how well they are responding to treatment at home. For clinically stable cats on insulin, blood glucose curves, or serum fructosamine concentrations where appropriate, should be assessed every three to four months. Cats with persistent signs of diabetes mellitus or episodes of hypoglycemia will need much more frequent follow-up until they are better regulated. It can take months to establish regulation in some cats, and there are some cats that can never be adequately regulated with treatment for diabetes mellitus.
