What is diabetes mellitus?

Diabetes mellitus is a medical condition resulting in an excessive amount of glucose or sugar in the blood. It is literally starvation in the face of plenty, because the body cannot utilize the glucose in the blood stream.  Glucose must attach to insulin, which then carries it into the cells to be used for energy.  A deficiency in insulin, which is a hormone secreted by the pancreas, leads to too much glucose in the blood and not enough glucose inside the cells where it is needed.

Diabetes mellitus affects an estimated one in four hundred cats, and is seen more frequently in middle to old-age cats and is more common in males than females.

What are the clinical signs of diabetes mellitus?

The clinical signs seen in diabetes are largely related to the elevated concentrations of blood glucose and to the inability of the body to use that glucose as an energy source due to the deficiency of insulin. The most common clinical signs seen in diabetic patients are an increase in water consumption and an increase in urination. Weight loss is also a common feature, and an increase in appetite may be noticed in some cats. Recognition of these signs is variable though, particularly because of the life-style of some cats. If a cat spends a lot of time outdoors, it may drink from ponds or pools of water outside rather than appearing to drink excessively from what is provided indoors. Cats that are fed canned or moist diets receive much of their water intake from their diet and increased water intake will be less easily recognized in these patients. 

How is diabetes mellitus diagnosed?

The diagnosis of diabetes mellitus is made based on clinical signs, persistently elevated blood glucose concentration and the presence of glucose in the urine. However, a diagnosis of diabetes cannot be made on a single blood and urine sample as other conditions, in particular stress, may also cause a transient rise in glucose levels. Confirmation of diabetes may therefore require more than one blood sample collected over a period of one to five days.  Measuring fructosamine can detect the average glucose levels over the past two weeks.

How is diabetes mellitus treated?

Diabetes mellitus is a treatable condition. Although long-term treatment requires commitment and dedication, it can be rewarding to successfully manage this condition in a beloved pet.

  • Removal of Predisposing Causes – Initial steps in treating a diabetic cat may involve removal of any predisposing causes for the diabetes. For example, the administration of some drugs predisposes cats to develop diabetes and withdrawal of these drugs may lead to resolution of the condition. Obese cats are more prone to develop diabetes and weight reduction can lead to resolution of the signs in some cats.
  • Dietary Intervention – Recent studies have shown that a small percentage of cats do not handle carbohydrates well in their diets.  Due to their unique metabolism, these cats gain weight even on low calorie diets when a large percentage of the calories are in the form of carbhydrates.  It appears that these same cats are the ones that are predisposed to diabetes, and many diabetic cats will become non-diabetic when they are put on a “Catkins Diet”.  It is very difficult to make a low carb dry diet, as starch is necessary to hold the kibble together.  Both the Hill’s m/d dry diet and the Purina DM dry diet are attempts at lowering the carbohydrates, but most endocrinologists think that cats must go to a canned-food-only diet to truly get the carbohydrates low enough to change the metabolism.
  • Oral Hypoglycemic Drugs – If the diabetic cat is stable, attempts may be made to treat the condition with oral medications.  Acarbose is a drug that inhibits uptake of glucose from the intestines, so it is often used in obese cats.  Glipizide is a drug that stimulates release of insulin from the cat’s pancreas, so it might help in borderline cases.  Although a small proportion of diabetic cats will respond to an oral hypoglycemic medication, most cats will require insulin injections to control the diabetes.
  • Insulin Injections – Most diabetic cats will require once or twice daily injection of a small dose of insulin.  Very small needles are available which cause no pain to the cat, and within a short time the procedure becomes routine.  Administration times, dosages and type of insulin for your cat will be determined by your veterinarian.  

Do treated cats need to be monitored?

During the initial stages of treatment, your cat will require several hospital visits and close monitoring at home until an appropriate insulin dosage is determined.  Most cats will achieve initial stabilization within a few weeks, but occasionally individual cats can be very difficult to regulate. 

It is important to monitor treatment to make sure it is working properly, and to determine if any insulin dosage adjustments are necessary.

Monitoring can be done in part through the collection of occasional blood samples by your veterinarian, but the most important monitoring is done at home.  It is particularly valuable to keep accurate records of the following information (check out logfrogapp.com for an online diabetic log):

*Daily records:                                                                       

  • Time of insulin injection                                             
  • Amount of insulin injected
  • Amount and time of food fed and eaten
  • Amount of water drunk
  • Approximate volume of urination

*Weekly record:

  • Weight of cat

*Monitoring Urine Glucose

In addition to these records, it can be valuable to monitor the quantity of glucose passed in the urine as a guide to the effectiveness of the treatment. This is easily done at home using Glucotests, which are confetti-like bits of paper sprinkled in the litter box.  These chips change color in the presence of glucose.  If urine glucose is consistently high (600), it may be necessary to increase the insulin dose.  If urine glucose is consistently low, it may be time to decrease or even stop the insulin.  Changes in insulin dosage should not be made based on a single Glucotest reading, and they should not be made without consulting with your veterinarian. Changes in the insulin dose are usually based on trends in urine glucose concentrations, as there is normally some day-to-day variation.

*Monitoring Blood Glucose Levels at Home

Sometimes it is advantageous to be able to accurately determine your cat’s blood glucose levels at home.  This is especially important in cats that are difficult to regulate, and in cats that may be becoming non-diabetic.  If it is indicated, your veterinarian can provide you with a feline glucometer and train you to obtain a tiny drop of blood from your cat’s ear tip for testing.

Guidelines for Giving Insulin

*We will regulate your cat’s insulin to his or her lifestyle.  The more consistent your cat’s routine, the easier it will be to control the diabetes.  If possible, we prefer that the cat eats a low carbohydrate meal morning and evening, when the insulin is to be given.  That way, the glucose taken in at the meal will start to rise at the same time the insulin is starting to take effect.  Also, meal feeding allows you to observe your cat’s attitude and appetite prior to giving insulin.  If your cat is sick or not eating, it is better to skip the insulin injection.  Appetite is harder to monitor if the cat grazes throughout the day, but it is possible to regulate diabetics that eat multiple meals.

*Insulin dosing should be done at a time that fits into your lifestyle as well as that of your cat.  Space out the doses as best you can, and be as consistent as possible, but dosing does not have to be exactly at twelve hour intervals.

*Insulin is a fragile drug, and it can be inactived by heat or vigorous shaking.  Pay attention to expiration dates.  Get in the habit of drawing up your insulin dose and returning the bottle to the refrigerator before your give the injection, to avoid the mistake of leaving the bottle out too long.

*Most human insulins are given with U-100 syringes (100 units per ml), while most feline insulins are given with U-40 syringes (40 units per ml).  Be sure that you are using the correct syringe for your insulin. If you must use a different type of syringe, you must use a conversion factor provided by your veterinarian.

*Always use a new needle and syringe for each dose of insulin.

*Insulin injections are usually given subcutaneously in the nape of the neck, but any place where loose skin is available is acceptable.  Occasionally injections must be given intramuscularly.

*When in doubt, do not give insulin!

What happens if my cat receives too much insulin?

If a cat receives too much insulin, it is possible for the blood sugar level to drop dangerously low. For this reason it is important to be very careful in ensuring the cat receives the correct dose of insulin.

The typical signs displayed by a cat with a very low blood sugar level are weakness and lethargy, shaking, unsteadiness and even convulsions. If a diabetic cat shows any of these signs it is important to seek immediate veterinary advice or attention. In mild cases of hypoglycemia, you may observe “wobbling” or “drunken” walk or appearance and the cat may not arouse when you call or pet them. In cases of mild or early hypoglycemia, you should administer approximately a tablespoon of corn syrup, honey or sugar solution by mouth. If more severe signs are displayed such as ataxia or severe incoordination and unsteadiness during walking, or convulsions, you should seek immediate veterinary care. Your veterinarian can advise you on specific emergency treatment of low blood sugar in your cat.

When in doubt, do not give insulin!

Diabetic cats get in trouble if their high blood sugar levels go uncontrolled for a long period of time.  High blood glucose for a few hours or a few days is not dangerous.  Low blood sugar can be life threatening.  If a cat receives too much insulin, of gets insulin when it is not diabetic, or gets insulin when the appetite is poor and the blood sugar is already low, it is possible for the blood glucose level to drop dangerously low.  For this reason it is important to remember that a diabetic cat that is acting sick or weak, or vomiting should never get insulin.  Talk to your veterinarian!

Diabetic Information Sources




Cobb Emergency Veterinary Clinic  (770) 424-9157

Manging Feline Diabetes