Diabetes mellitus is a condition in which the body cannot properly produce or respond to the hormone insulin. Insulin regulates the amount of glucose (sugar) in the bloodstream and delivers glucose to the tissues of the body to use as energy. Diabetes results in elevated levels of glucose in the blood. The most common form of diabetes in cats is type 2 diabetes. In type 2 diabetes, glucose levels are high because cells in the body do not respond appropriately to insulin.
Diabetes is the second most common endocrine disease in cats. (The body’s endocrine system consists of several glands—in the case of diabetes, that gland is the pancreas—that make hormones, which are chemical messengers to control organs throughout the body.)
Cats are typically diagnosed with diabetes between the ages of 10 and 13 years. More cats are acquiring diabetes as the number of overweight or obese cats grows. The average cat that weighs 13 pounds or more has about four times the risk of developing diabetes as a smaller cat. Signs of diabetes can include increased thirst, increased urination, weight loss, and increased appetite.
When a cat is suspected of having diabetes, a veterinarian will perform blood and urine testing. Diabetes is indicated if blood testing shows an elevated glucose level (hyperglycemia) and urine testing shows evidence of glucose in the urine (glucosuria).
Because stress in cats can lead to both hyperglycemia and glucosuria, another confirmation test called fructosamine is usually done. Fructosamine concentration reflects the average glucose concentration for the past 1 to 2 weeks and is not impacted by stress. If this test comes back as elevated, the diagnosis of diabetes is confirmed.
Insulin is the treatment of choice for cats with diabetes. This typically requires twice daily administration. In addition, dietary management can be an important component of managing diabetes in cats. A high-protein/low-carbohydrate diet is recommended. Weight loss is also an important component of diabetic management in overweight cats. Weight loss, if attempted, should ideally be gradual, one-half percent to 1% of total body weight lost per week.
The goals of treatment are to maintain a healthy blood glucose, stop or control unintended weight loss, stop or control increased thirst and urination, and avoid hypoglycemia (low blood glucose).
Unlike dogs, cats can reach diabetic remission; these cats have near-normal blood glucose levels without receiving insulin or other blood-sugar–lowering medication. However, cats in diabetic remission require close monitoring to ensure that they do not relapse. Remission is not achievable in every diabetic cat.
Blood glucose curves are used to monitor response to insulin dosing. If a blood glucose curve is performed at home, pet owners measure the first blood glucose reading before the insulin injection. Then, they test every 2 to 4 hours until the next dose of insulin, depending on the type of insulin used. Performing curves at home eliminates the stress of coming to the clinic, which can affect the accuracy of the testing. Owners may need to perform a blood glucose curve several times to find the right dose for their cat.
One method of measuring glucose is by using a glucose meter calibrated for feline blood, such as a AlphaTRAK3. Another way is by using a continuous glucose monitor, such as a FreeStyle Libre. These monitors can be picked up at a human pharmacy and installed by a veterinarian or veterinary technician. Other important monitoring tests include serial bloodwork and urine testing. Your veterinarian will help determine the frequency at which these tests should be performed.
Monitoring your cat’s level of thirst and urination, weight, and appetite are important throughout treatment. These measures can give clues as to how well the diabetes is being managed. Unfortunately, monitoring response to treatment in diabetic cats can be frequent and expensive.
Complications of Diabetes
One complication of diabetes is diabetic ketoacidosis (DKA). This problem occurs when there is not enough insulin in the body to control the amount of glucose in the blood. DKA happens in uncontrolled diabetics. Without the proper amount of insulin in the body, glucose cannot be used as an energy source. Instead, the body breaks down fat, which produces ketone bodies. With high levels of ketones, the body becomes more acidic, which disrupts fluid and electrolyte balance. Left untreated, the resulting abnormal electrolyte balance may lead to abnormal heart rhythms and muscle function and death. Signs of DKA can include increased thirst or urination, lethargy, weakness, vomiting, increased respiratory rate, decreased appetite, and weight loss.
The other complication is hypoglycemia, or low blood sugar, which may arise when insulin therapy lowers the blood sugar significantly. Signs of hypoglycemia include weakness, lethargy, vomiting, lack of coordination, seizures, and coma. Hypoglycemia can be fatal if left untreated. A diabetic cat that shows any of these signs should be offered its regular food immediately. If the cat does not eat voluntarily, it should be given oral glucose in the form of honey, corn syrup, or dextrose gels and brought to a veterinarian immediately. However, if a cat is seizing or comatose, oral glucose methods should not be attempted.
If you’ve noticed changes to your cat’s eating and drinking habits as well as weight, please have them seen by a veterinarian for additional testing to be done as soon as possible.
By Jeanette Barragan, DVM