Diabetes Mellitus (Diabetes) in Cats

Diabetes Mellitus (Diabetes) in Cats

Animals Affected

Cats of any breed, usually middle-aged.


Diabetes mellitus (known simply as diabetes) is a common and serious disease of cats. The main characteristic of diabetes is an inability to control the level of sugar in the blood. This leads to chronically high blood sugar levels, which in turn lead to the symptoms of the disease.

Management of diabetes in cats is challenging but, in most cases, it is successful. With proper treatment, many diabetic cats lead essentially normal lives. However, without treatment the disease inevitably leads to serious complications.

Diabetes in cats is similar to type 2 (adult onset) diabetes in humans.


Symptoms of diabetes include:

Risk Factors

  • Obesity is the leading risk factor for diabetes in cats.
  • An individual genetic or hereditary predisposition to diabetes very likely is involved in most cases.
  • Dental disease leads to chronic inflammation which may predispose cats to diabetes.
  • Some authorities contend that high levels of sugar and carbohydrates in dry commercial cat foods play a role in the development of diabetes. However, this belief is not universally accepted.  Recent studies have not found a link between dry food consumption and diabetes in cats.
  • Some medications, especially prednisone or depo-medrol (a long-acting, injected form of prednisone) can trigger diabetes.


  • Untreated diabetes leads to emaciation, chronic lethargy and weakness.
  • Diabetic cats are prone to urinary tract infections. House soiling may occur as well, due to increased frequency of urination.
  • Insulin administration is the main method of treating diabetes in cats. However, some cats may be subject to accidental overdose. This has the potential to be fatal. The article titled “Insulin” has more information on the signs and prevention of insulin overdose.
  • Diabetes can lead to limping in the rear legs.
  • Diabetic cats have weakened immune systems and are at increased susceptibility for all types of infections.
  • Untreated diabetes, over time, may lead to potentially fatal syndromes including diabetic ketoacidosis (DKA), and nonketotic hyperosmolar syndrome. These syndromes require hospitalization and intensive care and monitoring. Even with appropriate treatment, cats suffering these syndromes may not survive. Therefore, preventing these syndromes is a core goal in the management of feline diabetes.


In most cases, simple blood and urine tests provide a conclusive diagnosis by showing elevated levels of sugar in the blood and urine.


Insulin administration is the mainstay of managing diabetes in cats. The most commonly administered forms of insulin are PZI and glargine (also known as Lantus®). Insulin must be administered once or twice daily by injection. Generally, the owner of the cat administers the insulin. After initiating insulin treatment, follow-up diagnostic testing and monitoring are be necessary at regular intervals to ensure proper dosing. It is critical to follow the recommendations of your veterinarian carefully at all times.

Administering insulin injections to cats is daunting to most owners during the initial stages. However, the vast majority of people who care for diabetic cats are able to master the task within a few weeks.

Switching diets may help to regulate blood sugar levels and manage diabetes. The most commonly used diets are low in carbohydrates (such as Purina Veterinary Diets Diabetes Management). However, some veterinarians advocate using diets that are high in fiber.

Oral anti-diabetic medications such as glipizide and acarbose are sometimes used in the treatment of feline diabetes. However, these medications generally are not as effective as insulin.

Proper management of concurrent diseases (such as periodontal disease or bladder infections) helps to stabilize and control diabetes.


Every individual will have a unique response to insulin or oral diabetic medications. Therefore, intensive monitoring is necessary after treatment has begun.

The most commonly employed method of monitoring a cat’s response to insulin is to run a series of blood sugar measurements over several hours. This battery of tests is known as a blood glucose curve, and it provides insight into the strength and duration of the insulin’s effect.

Most veterinarians hospitalize cats for the duration of blood glucose curves. However, some newer methods may permit home measurement of blood sugar by the owner. In either case, the veterinarian will use the results to assess the efficacy of the insulin and, if necessary, change the dose.

Often, several cycles of insulin adjustments followed by blood glucose curves are necessary to achieve adequate control of the disease.

Once diabetes is adequately controlled, symptoms such as lethargy, poor coat quality, and changes in water consumption may decrease. However, this is not always the case. As mentioned above, the core goal of diabetic management is to prevent the potentially fatal complications that occur when the disease progresses unchecked. Therefore, even with successful treatment, some of the outward symptoms of the disease may persist.

Cats with diabetes may experience changes in the intensity of their disease, resulting in changes in the need for insulin. Because of this, periodic blood sugar curves must be run even in cats with well-managed diabetes.

Some owners of diabetic cats rely on home test kits for sugar in the urine as a method of monitoring treatment of diabetes. These kits are convenient and they offer some degree of insight into how well diabetes is controlled. However, most experts agree that this method not as accurate or reliable as blood testing.

Blood tests known as fructosamine or glycosylated hemoglobin are used in some cats to provide a picture of long-term control of diabetes. In most cases they are used in combination with blood glucose curves to obtain a more complete picture of diabetes management.

Special Issues Regarding the Use of Insulin

Although insulin is instrumental in treating feline diabetes, it requires special handling and administration. There is a risk of overdose, which can be fatal. For detailed information on the prevention of insulin overdose in cats, as well storage and handling of insulin, please see the article entitled Insulin.


If diabetes is caught early and treated aggressively, some cats with the condition can be cured and maintain normal blood sugar levels without treatment. However, cats who have been cured of diabetes remain at high risk of relapse.

Blood sugar measurements in cats with diabetes may be much higher than those of humans afflicted with the disease. In cats, measurements higher than 600 mg/dL are not uncommon.

Feline diabetes is similar to type 2 (adult onset) diabetes in human beings. However, unlike humans, cats typically do not suffer poor circulation, nor require amputation of digits or limbs.

Forms of insulin that can be administered by methods other than injection may be available soon. Alternative administration methods under development include inhalable insulin, and insulin administered by eye drops. At this time, however, injecting insulin is the gold standard of treatment.

Some experts advocate performing blood sugar measurements and full blood glucose curves at home using human instruments. There are many benefits to this method. Key among them is that it eliminates the need to hospitalize the cat for the duration of the test. Unfortunately, difficulties with calibration of human instruments and the reluctance of some owners to collect blood samples from their cats have hindered the conversion to this method.

Copyright © Eric Barchas, DVM All rights reserved.
The contents of this page are provided for general informational purposes only. Under no circumstances should this page be substituted for professional consultation with a veterinarian.