Educational Resources

Feline Diabetes

Diabetes mellitus is an endocrine disease in which the blood sugar level rises because of the failure of insulin to control it. This occurs either because the pancreas has lost its ability to manufacture insulin (known as Type I diabetes) or because the mechanisms of insulin release and tissue responsiveness are dysfunctional (Type II diabetes). Without proper insulin regulation, the body is unable to transport glucose (a simple sugar obtained from digested food) into cells. Because glucose remains trapped in the bloodstream, the tissues of the body are deprived of the energy needed to function normally.

Risk factors
In many cases, the cause for why a cat has developed diabetes cannot be determined. However, it is known that obesity predisposes cats to Type II diabetes. Other causes or factors include damage to the pancreas caused by inflammation, infection, immune-mediated disease, tumors, genetic predisposition, and exposure to certain drugs. Cats receiving steroids are also predisposed to diabetes.

The most common symptoms of diabetes are weight loss (often with a healthy appetite), excessive water consumption, and excessive urine output. Because so much urine is being produced, some diabetic cats will urinate in unusual places (i.e., outside of the litter box). Owners may notice that litter has suddenly begun to stick to their cat’s paws because of the excess volume of urine being produced. Some cats will also show weakness, lethargy, vomiting, abnormal gait, poor grooming habits, and changes in behavior.

Physical examination may show poor body condition, dehydration, jaundice, and an enlarged liver. Laboratory testing is essential to diagnose diabetes. Blood tests show hyperglycemia (high blood sugar, usually above 300 mg/dl), and often there are liver enzyme abnormalities. In complicated cases, there may be electrolyte imbalances and acidosis (acidic blood). Urine samples will show high levels of glucose and in some instances, infection.

Blood and urine tests are required for several reasons: 

  1. The common symptoms of diabetes are similar to those of other diseases, especially kidney disease, hyperthyroidism, and cancer
  2. To detect other illnesses that may complicate the management of diabetes and
  3. The severity of diabetes will determine initial treatment options and prognosis.

Successful management of the diabetic cat is a challenge for both owners and veterinarians. Recommendations regarding the treatment of feline diabetes are constantly evolving, and there is no standard protocol by which all cats can be treated. Treatment requires a time and financial commitment on your part: your cat will require daily medication and feeding at consistent times, there will be frequent visits to our office, and you will need to monitor changes in your cat’s behavior to help guide us in the management of the disease.

Modes of treatment

Insulin injections — Insulin is the cornerstone of the treatment of most diabetic cats. Although your cat may not be placed on insulin injections (shots) immediately, many diabetic cats will eventually require insulin to successfully manage their condition. Currently, insulin can only be given by injection. There are two commonly used forms of insulin, Glargine (Lantus™) and protamine-zinc (Pro-Zinc™) insulin.

Glargine insulin — Is long-acting insulin commonly used in human diabetics. Although it is not approved specifically for use in cats, it is often used in newly diagnosed diabetics because it is the insulin that is most likely to cause cats to convert back to the non-diabetic state (go into remission). Given this fact, frequent blood sugar checks either by the owner at home or at the veterinary office are recommended.

Pro-zinc insulin — Is a long-acting human recombinant insulin approved for use in cats. This insulin is dilute insulin and dosed using a special type of insulin syringe. The syringes and insulin are only available through veterinarians.

Dietary therapy — Because cats are obligate carnivores, they require a diet high in protein and low in carbohydrates.  Canned foods most closely resemble the natural diet of cats and also help to increase fluid intake. We often use these diets for weight loss in diabetic and non-diabetic cats. In some instances, cats on canned-only diets will reverse their need for insulin therapy.

Some cats will overeat when allowed constant access to food, which may worsen the diabetic condition. If your cat eats all the food that is offered at mealtimes, feed the cat twice a day in conjunction with the insulin administration. If your cat refuses to eat canned foods, we can discuss ways to train them to accept them or you can try the high protein dry diabetic diets.

*Please note* If your cat will not eat food and insulin is given, low blood sugar (hypoglycemia) may result and can be a life-threatening emergency. Please do not try to force your cat to eat a certain diet.

Cats that are being managed with only diet modification are usually checked within 2-4 weeks. An examination and blood glucose measurement will evaluate whether the diet alone is effective. When to next perform re-check exams and blood glucose measurements will be determined at that time.

Cats that are placed on insulin typically have an examination and blood sugar determination made after a week or two of therapy. The dose of insulin may then be adjusted depending on the cat’s response. At that time, we will also determine when a recheck examination and blood sugar measurement should next be made.

Some owners may be interested in taking blood glucose measurements from their cats at home. These measurements may be a better reflection of the cat’s true blood sugar, as visits to the veterinary hospital can sometimes induce stress hyperglycemia (elevated blood sugar due to stress).  These measurements would then be shared with your veterinarian to determine insulin response. Owners that are not comfortable with at-home monitoring can choose to bring the cat to the veterinary hospital, as directed by the veterinarian.

Complete blood work and urinalysis should be conducted to monitor for changes in liver values, monitor for infection, and check general health status semi-annually or as recommended by your veterinarian. Your veterinarian may also recommend checking a fructosamine level. Blood fructosamine is a measure of glucose bound to proteins in the blood and reflects the average blood sugar over the past 1-3 weeks.

Complications of Diabetes

In general, diabetic cats suffer fewer secondary problems than humans or dogs. They do not develop kidney failure, skin infections, or circulation problems.  Most complications occur because of inadequate control of the disease and may include:

  1. Peripheral neuropathy (a condition affecting the nerves to the legs, head, and tail) — This is a relatively common problem that initially appears as weakness in the hind legs. The cat generally walks so that its hock (the ankle joint) is touching the ground rather than just its toes. The owner may notice difficulty jumping or using the litter box properly. The nerves in the front legs may also be affected so that the carpus (the wrist joint) sinks toward the ground as well.  As the condition progresses, nerves in the head, neck, and tail may also be affected causing a generalized weakness.  Neurologists believe this condition does result in some discomfort, especially in the extremities (lower legs and paws). Cats with well-regulated diabetes are less likely to develop this condition, and cats that have developed the condition may improve once the diabetes is controlled.
  2. Ketoacidosis — This is a potentially fatal condition that develops when diabetes is uncontrolled or untreated. When the body is deprived of sugar as an energy source, it begins to break down fat stores for energy instead. The by-products of fat metabolism include ketones, which are acids that have toxic effects on the brain and other tissues. These cats are quite sick and symptoms include severe lethargy, poor appetite, vomiting, abdominal pain, and coma. The electrolyte imbalances and dehydration that can occur with this condition are often severe and potentially life-threatening requiring hospitalization and intensive treatment.
  3. Hypoglycemia (low blood sugar) — This is almost always associated with an overdose of insulin, but may also occur if the insulin requirements of the cat change. See the section on giving insulin injections for information on how to spot and avoid hypoglycemia.
  4. Urinary Tract Infections — Diabetic cats lose glucose in their urine. The sugar provides energy for bacteria to colonize the bladder.
  5. Hepatic lipidosis (fatty liver disease) — This potentially treatable disease occurs when the liver begins to mobilize fats to use as energy due to either decreased appetite or increased need for utilizable energy. The excess accumulation of these fats within the liver leads to liver failure. Symptoms may include lethargy, poor appetite, vomiting, and jaundice. Treatment often requires hospitalization for fluid therapy, correction of electrolyte imbalances, and supplemental feeding, which may include placement of a feeding tube.
  6. Pancreatitis and pancreatic digestive enzyme deficiency — Although not a consequence of diabetes, this condition often is present in diabetic cats. Chronic inflammation of the pancreas can lead to scarring and degeneration of pancreatic tissue. The pancreas is responsible for the production of digestive enzymes as well as insulin. When a cat becomes deficient in digestive enzymes, exocrine pancreatic insufficiency (EPI) may occur. Symptoms include diarrhea, frequent or large bowel movements, pale-colored stool, weight loss, and vomiting. Treatment consists of adding pancreatic enzymes to meals.

We are often asked how long a cat will live if it has become diabetic. Because of the extreme variability among diabetic cats, this question is difficult to answer.  In general, our impression is that diabetic cats have a shorter life span than average. However, many cats can live for years following diagnosis if appropriate therapy is given. Also, there is a small percentage of cats that can go into diabetic remission either temporarily or sometimes permanently if treatment is initiated early in the disease.

Insulin Therapy

This guide will help you understand how to give injections, how to store and handle insulin, and problems that may occur while your cat is on insulin therapy. We want to make you as comfortable as possible with the treatment and will address all of your questions and concerns.

Demonstration of insulin injections
We will schedule a time for one of our veterinary technicians to show you how to give injections. Information provided during this session (which lasts 10-20 minutes) will include how to measure the dose of insulin, where and how to give the injection, and how to store and handle insulin.

Timing of the insulin injections
You will be giving insulin either once or twice a day (most cats will need morning and evening doses). If your cat has been prescribed injections only once a day, it is best to give it when the cat eats the most. For most people, this is in the morning when fresh food is put down. If you have been instructed to give injections twice a day, the injections should be as close to 12 hours apart as possible, and no sooner than 10 hours apart unless your veterinarian has instructed otherwise. If you cannot give a dose or miss a dose, it is better to skip that dose than to try to double up on injections. Return to regular dosing at the next scheduled injection.

Where to buy insulin and insulin syringes

  • Glargine insulin (100 units of insulin per ml, U-100): You will need a prescription for this insulin and may get it at any human pharmacy. The U-100 (orange capped) insulin syringes may be purchased from a veterinary hospital or any pharmacy.
  • Pro-Zinc insulin (40 units of insulin per ml, U-40): You will need to buy the insulin and special U-40 (red-capped) syringes from a veterinary hospital only.

Storage and care of insulin
Insulin should be kept in the box, in refrigeration. Prolonged exposure to direct light (especially sunlight) or excessive heat will inactivate the insulin.  A few hours at room temperature in room light (e.g., being left on the kitchen counter) is unlikely to change the insulin activity. For Pro-Zinc, the insulin bottle should be gently rolled and inverted several times before it is given to the cat.  It should never be vigorously shaken or it may become less effective. Failure to gently mix the insulin before giving could result in over or under-dosing. Pro-Zinc insulin may be stored for 4 months with refrigeration. Glargine insulin does not need to be mixed and the insulin may be stored in the refrigerator for 6 months. If insulin is left at room temperature for greater than 12 hours, the bottle will only be good for 1 month.

Disposal of insulin syringes
Because of public health concerns, used insulin syringes should not be thrown away in your regular garbage. A hazardous waste container will be provided from our hospital during the insulin administration demonstration. When full, you may bring it in and we will dispose of the container properly and purchase a new one.

Monitoring Recommendations for Cats on Insulin
Initially, your cat will need to be monitored frequently as the dose of insulin is adjusted. If you choose, we can train you on how to take blood sugar measurements at home. This may reduce the amount of stress placed on your cat. The measurements would then be shared with your veterinarian and the dosage and timing of the insulin may be adjusted. If measurements are not made at home, you will be required to bring your cat in periodically (recommended times to be outlined by your veterinarian) for examination and blood sugar measurement. We do not generally recommend serial blood glucose monitoring in our feline patients, as the stresses of hospitalization may affect your cat’s appetite and may also falsely elevate blood sugar levels. However, in some cases, we may suggest a serial blood glucose test to determine the correct dose of insulin needed or to assess response to current insulin therapy. We strongly recommend a physical examination and full blood work and urinalysis every 6-12 months.

Websites for Information on Diabetes Mellitus

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