(based on lecture notes from Deborah Greco DVM PhD ACVIM)

Regrettably, we have an epidemic of obesity and diabetes in cats and it appears that the cause of these problems is dry cat food. Cats are carnivores…they are meat eaters and over 90 percent of their natural diet is meat. Cats have been eating a protein diet for 120 million years and in the past 20 plus years we have changed their diet to dry food. Dry food is convenient but dry food is approximately 40% carbohydrates and this high carb diet is making our pets fat and prone to diabetes.

Cat physiology is different from other animals, especially in glucose metabolism. Most information about feline diabetes has previously come from human and dog studies and are NOT relevant to cats. Cats metabolize carbohydrates (glucose, starch, sugar) differently than humans and dogs. If we treat feline diabetes just like human diabetes, a lot of cats are going to be in trouble.

Neutered male cats over 13 pounds are at high risk of developing diabetes and should be considered pre-diabetic. Orange cats are particularly prone to diabetes. So if your cat is overweight, the best advice I can give you is to feed canned food 2.5 to 3.5 ounces twice a day and avoid dry food completely. No free feeding of cat foods!

Other thoughts concerning Diabetes in cats:

  1. If a cat develops diabetes after receiving steroids, the steroids did not cause the diabetes but simply "unmasked" it. These cats were already having glucose metabolism problems and would have eventually developed diabetes even without steroids.
  2. Some studies show that 50% of diabetic cats have pancreatitis. Current therapy is leaning toward continuing to feed cats with pancreatitis and to treat with Medrol.
  3. Clinical signs can judge diabetic control: such as PU/PD, loss of weight, gain of weight (over use of insulin?) and the presence of neuropathy. We don’t need to perform serial blood glucose curves to know that your cat is unregulated.
  4. Fluctuations in glucose levels cause neuropathy in cats and cataracts in dogs. Glucose curves can help evaluate great swings in blood sugar levels. In a blood glucose curve for the cat, the difference between the highest and lowest blood glucose levels should be less than 150 mg/dl. For example, a cat that stays around a steady 200 mg/dl for blood glucose has fewer complications than a cat whose blood glucose ranges from 80 to 280 mg/dl.
  5. If a cat is male and weighs more than 13 pounds, they are prone to hypoglycemia without warning when being treated with insulin. (See hypoglycemia at end of this handout)
  6. Chromium is essential for cats. Chromium is lost in the urine, so if your cat has PU/PD, it needs chromium supplements of 200-600 mcg/day. Even the best commercial diets provide only 24 mcg of chromium/1000 kcal. Bacon and pork rinds are a great source of chromium. These are good treats for your cat. 

Treating Diabetes in Cats

Insulin therapy accounts for 20% and diet accounts for 80% of diabetic control.  Prozinc is the insulin of choice for cats.  Prozinc insulin is 40 U/ml so be sure to use 40 U insulin syringes. If you are switching to Prozinc insulin, the client’s must use the proper 40 U syringes.

Most cats can be controlled on 2 units of Prozinc insulin injections given twice a day and canned food. Most cats have been diabetic a long time so rapid control of blood sugar is not necessary. We never put a cat on more than 3 units of insulin BID without doing an endocrine workup. Chances are, a cat needing this much insulin has some other problem. And before doing an endocrine workup, go through the "punch list" for owner compliance first.

Give diet a fair chance because 70% of type II diabetic cats will come off of insulin and be controlled with diet alone.

If your cat is receiving regular subcutaneous fluid injections, do not inject insulin near the area where fluids are administered.

The scruff of the neck the worst site to inject insulin because it has a poor blood supply and is prone to forming scar tissue and granulomas. Because of these characteristics, insulin is absorbed very irregularly from the scruff. The lateral thorax and abdomen are much better sites. Injection sites should be rotated to decrease scar formation and improve absorption.

If we can’t regulate your cat or your cat has been stable on one insulin dose and then changes, the first thing we need to check is owner management errors using the following "punch list".

Punch List for Owner Compliance

  • Are injection sites being rotated?
  • Is injection being done in the proper place?
  • Is the insulin being stored properly (some should NOT be refrigerated: check the vial)
  • Is the insulin too old or has improper handling damaged it?
  • Does the owner have good injection technique?
  • Is the client compliant with diet? (All canned, low-carb food; no free-feeding)

Monitoring Diabetes: 
We rely on the owner’s observation for recurrence of clinical signs in conjunction with periodic physical examinations and blood and urine tests. Most important is the owner's opinion of water intake, urine output, appetite, stool consistency, and body weight. If these factors are normal, the diabetic cat is usually controlled.

Urine testing

We want everyone to home monitor urine sugar levels with Purina’s Glucotestâ. Urine testing is fairly easy and an accurate way to judge regulation and it is a lot less expensive and stressful than blood glucose curves. Glucotestâ confetti is added to litter and the color change is compared to the box.

  • Negative urine glucose for two days: lower insulin dose 1 unit
  • Trace to 1 plus urine glucose: keep dose the same
  • Persistent 3 or 4 plus urine sugar: evaluate owner’s compliance with diet and punch list. Be patient when changing insulin doses. Allow 10 days or more for adjustment to a new insulin dose. It may take some time for the urine sugar to drop. Believe the cat! If the symptoms are controlled don’t rush to change dose or switch insulin.
  • The owner is never allowed to raise the dose of insulin without consulting her veterinarian.

Never put a cat on more than 3 units of insulin twice a day without doing an endocrine workup. Chances are, a cat needing this much insulin has some other problem. And before doing an endocrine workup, go through the punch list for owner compliance first.

Additional Testing

  1. General health profiles every 6 months are necessary to monitor the health of your cat
  2. Serial blood glucose measurements (Blood Glucose Curve) may be necessary to determine insulin dose. This procedure may be stressful to some cats and fortunately, we have had good results in judging regulation with urine glucose testing and Fructosamine levels.
  3. Fructosamine is an important blood protein. The blood levels of Fructosamine are directly related to blood glucose level. Thus, a high Fructosamine level is indicative of poor diabetic control over the last 4 to 6 weeks.
  4. Urine tests are necessary to look for the presence of ketones (Ketoacidosis), the presence of glucose and bladder infections.

Hypoglycemia (Low Blood Sugar)
It is important for parents of diabetic cats to understand, in advance, the proper actions to take for this life threatening condition. Giving too much insulin, giving the wrong insulin, not eating, or having a cat that spontaneous converts to non-diabetic status may cause hypoglycemia.

Symptoms of Hypoglycemia

Early signs include

  • Trembling
  • Nervousness
  • Anxiety
  • Hunger

More Severe Signs

  • Poor balance
  • Weakness
  • Seizure
  • Coma.






Treatment of Hypoglycemia

  • Give food if your pet will eat.
  • Provide oral sugar. Corn syrup (Karo syrup), honey, or maple syrup is absorbed from the mouth and gums. Apply syrup to gums and gently rub to aid absorption.
  • If symptoms are severe, begin oral treatment and seek veterinary help.
  • Do not repeat insulin


pdfDiabetes in Cats.pdf61.15 KB

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