Hallett Veterinary Hospital

5744 Brown Street
Oconomowoc, WI 53066



Diabetes Mellitus in Cats

Background information:
Diabetes mellitus is a deficiency of insulin, a hormone required for the body to utilize blood glucose (sugar) for energy.

Due to lack of glucose usage, blood glucose levels increase, and above a certain level, glucose spills into the urine, causing increased urine production, and consequently, thirst. Inability to use glucose causes the body to shift metabolism to fats and protein, resulting in weight loss, and occasionally a serious complication called ketosis or ketoacidosis.

Diabetes usually occurs in middle aged or older cats, but may sometimes be seen in any age, both male and female. As described above, the signs include increased thirst and urination, and weight loss, often with increased appetite.

Other diseases that may cause some or all of the same signs are hyperthyroidism, kidney or liver disease, intestinal or digestive disease, and some forms of cancer. Therefore, diagnostic tests are necessary to confirm diabetes.

Diagnosis is made by demonstrating persistently elevated blood glucose levels and the presence of glucose and/or ketone's in the urine.

Insulin: Most cats require insulin for long-term control of diabetes. Insulin is given by injection under the skin, once or twice daily. When starting insulin, blood glucose must be monitored to determine the insulin dose. Then, a glucose curve (blood glucose every 2 hours for a day) is done to determine the day’s lowest glucose level, at what time this occurs, and the optimum dosage frequency (once vs. twice daily). The insulin dose, type, and frequency are then adjusted accordingly. Many cats are difficult to regulate and require multiple glucose curves.

Home monitoring of appetite, weight, activity level, water consumption, and urination is very important. Long term laboratory monitoring is done with glucose curves or serum fructosamine every 6 months, or any time a dose change is needed.

Diet: The ideal diet is relatively high in fats and proteins, high in soluble fiber, and low in simple sugars. Research into the effects of diet continues.  Recent data suggest that with appropriate diet and the use of a new insulin preparation called insulin glargine, more than half of newly diagnosed diabetic cats will return to a non-diabetic state within a few months.  The current recommendations are Purina DM, or OM for overweight diabetics.

Overweight diabetics should lose weight very gradually, no more than 1 lb. per month. Underweight patients should not be fed high-fiber foods until their weight is normal. Whichever diet is recommended by your veterinarian, it should be fed twice daily, at the time of each insulin injection. If insulin is only given once daily, the two meals should be at the time of insulin injection, and at the expected peak effect of the insulin (see "glucose curve" below). Some cats fare well with free-choice feeding, but monitoring the cat’s food consumption becomes more difficult this way. Note: if the cat does not eat a meal, insulin should not be given; if the cat misses more than one meal, it should be examined as soon as possible.

Control of Infections: Infection can cause resistance to insulin, making diabetes more difficult to control, and complications more likely. Common sources of infection are dental disease, urinary tract, and GI tract or liver. Conversely, diabetic patients are more susceptible to infection.

The most serious complication of insulin treatment is hypoglycemia, or low blood sugar. If too much insulin is injected, the dose is given twice by mistake, the patient does not eat a normal amount of food, or the patient’s insulin requirements have decreased, an overdose may occur, causing hypoglycemia. The symptoms, in order of severity, are:

tremors or twitching

If signs of hypoglycemia occur:

Feed the cat if it is able to eat. If not willing to eat, but still conscious, put corn syrup in the mouth or on the gums.

Bring the cat to the regular veterinarian if available, or to an emergency clinic if hypoglycemia occurs after normal hours.

Other complications can arise from insufficient insulin or poor response to insulin treatment. This can result in persistent symptoms of diabetes or progression to keto-acidosis, a life threatening alteration in metabolism and electrolyte balance.

Uncontrolled diabetes can lead to nerve dysfunction, usually seen as weakness in the rear legs and walking on the hocks (ankles) instead of the normal stance. The skin and hair coat can also be affected. Urinary tract infections are more common in diabetics, due to the glucose in the urine providing ideal nutrients for bacteria.

Monitoring:Once diagnosis has been confirmed, the following testing will be necessary, depending on each pet’s condition and response:

Baseline fructosamine
Measure (or estimate) water consumption +/- urine production.
Initial Regulation: Blood glucose 4-6 hours after insulin; adjust dose until near normal, then
Glucose Curve: Blood glucose every 2 hours throughout the day; determines the day’s low point and duration of effect, which dictates the dosage schedule and may indicate need for an alternate type of insulin.
Fructosamine: Because some cats’ diabetes seems well controlled at home, but have abnormal glucose levels in the hospital (due to stress), glucose curves may not be sufficient for monitoring these patients. Fructosamine measures the average glucose levels over a period of several weeks, which can be compared to the baseline levels initially measured.

Home monitoring:
Though insulin dose adjustments should not be made without blood test results, home monitoring of body weight, appetite, water consumption, and urination can alert the owner to potential problems.

Persistent thirst and excessive urination usually indicate that the diabetes is poorly controlled. This can be due to an insulin dose that is too low or too high, or insulin that has too short a duration.

Return to normal appetite and water consumption with stable body weight is a good indication that the diabetes is well controlled, even if laboratory tests are still abnormal.

Urine Monitoring for Select Cases:

Urine test strips that test for glucose and ketones are available from the pharmacy. Collection of urine at home can be done by confining the cat to a small room with a clean litter pan using small plastic beads (Poly-fil) in place of litter.

If urine glucose is negative 3 days in a row, hypoglycemia may be a concern; have blood glucose checked before any more insulin is given.

If urine glucose is >500mg/dl (1/2 %) 3 days in a row, the diabetes is poorly controlled; a glucose curve should be done to determine if a different dose, type or schedule is indicated.

If ketones are present more than once in several days’ time, the diabetes is probably poorly controlled, and other problems may be present which could result in ketoacidosis. The cat should be examined as soon as possible.