Note for Pet Owners:

This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

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Diabetes mellitus is common in humans and in pets in which it is reported to affect about 1 in every 200 dogs, and one in every 800 cats

Diabetes mellitus is "a disorder of normal glucose homeostasis resulting from a relative or absolute deficiency of insulin ".

There are two basic forms of the disease :

  • Insulin dependant diabetes mellitus (IDDM) -  the majority of cats and dogs fall into this category
    • This is due to a failure of the pancreas to produce sufficient insulin, and it can be present from birth, or develop later
  • Non-insulin dependant diabetes (NIDDM)
    • Insulin is produced in sufficient quantities by the pancreas, but it is unable to work because of resistance in the target tissues. This "insulin resistance" can be caused by a variety of situations :
      • Obesity
      • Various diseases - eg heart failure.


Diabetes can occur :

  • spontaneously (primary)
    • congenital islet cell hypoplasia
    • Acquired senile atrophy or
  • secondary to other conditions :
    • pancreatitis
    • obesity
    • iatrogenic administration of, or any disorder that increases, circulating  hormones antagonistic to insulin :
      • androgens
      • catecholamines - eg heart failure
      • glucagon
      • glucocorticoids
      • growth hormone - eg acromegaly
      • oestrogen
      • progesterone

Even before they show signs of diabetes, dogs that are obese have impaired blood sugar control, and they have increased concentrations of insulin in their blood due to insulin resistance. In one large survey obese cats had over twice the risk of developing obesity as non-obese cats. So keep your pet lean, fit and trim.

Breed Occurrence
It is most common in middle-aged to old small dogs including Dachshunds, Poodles and Terriers, but it is also seen in larger breeds - Samoyeds, Alaskan Malamutes and Rottweilers  

Most cases occur during middle-age - to old age (7-9 years). In adult dogs bitches account for 66% of cases  In cats there is no diffence  in incidence between the sexes.

Siamese cats are thought to be predisposed to develop diabetes as is  the Burmese which is over-represented and therefore at risk to develop diabetes, and 90% of cases occur in cats over 6 years of age. Obesity more than doubles  the risk of developing diabetes in cats.


In uncomplicated diabetes mellitus the cardinal signs are :

In bitches signs often occur soon after a season.

In the body insulin helps sugar (as glucose) move into tissue cells where it is used to produce energy. If there is insufficient insulin present, or if the insulin that is present can not work because of tissue resistance, blood sugar concentrations rise. Eventually the sugar "tips over" into the urine, and this takes water with it. The result is an increase in urine production and because the animal is effectively losing water from it's body it needs to compensate and so it develops an increase in thirst. If your pet develops an increased thirst one of the disorders that your veterinarian will probably screen for is diabetes. Blood tests and urine tests will help to confirm the diagnosis.

Because the glucose in the blood can not get into the tissues that use it for energy (eg the brain), these tissues can't function properly. The animal eats more food (called polyphagia) in a vain attempt to increase glucose supply to it's tissues, even though there is plenty already in the bloodstream.

In advanced diabetes complicated by the presence of ketoacidosis the following signs might also be present:

  • Depression
  • Inappetance/anorexia
  • Vomiting +/- diarrhoea
  • Tachypnoea
  • Jaundice (especially in cats)
  • Oliguria or anuria in later stages
  • Coma

Liver involvement is secondary to the diabetic state. 

Diabetes mellitus is confirmed by diagnostic tests , and diabetes must be differentiated from other causes of polydipsia and polyuria including :

  • Diabetes insipidus
  • Fanconi syndrome
  • Hyperadrenocorticism
  • Liver failure
  • Psychogenic polydipsia
  • Pyometra
  • Stress glycosuria (especially cats)
  • Renal disease

Blood tests 

Fructosamine values (micromol/l)

Non-diabetic 225-365
Recently diagnosed 320-850
Treated - excellent control 350-400
Treated - good control 400-450
Treated - fair control 450-500
Treated - poor control 500+
Non-diabetic 190-365
Recently diagnosed 350-730
Treated - excellent control 350-400
Treated - good control 400-450
Treated - fair control 450-500
Treated - poor control 500+
Limitations of fructosamine tests are : cannot detect short-term changes eg hypoglycaemia, hyperthyroid cats with concurrent diabetes may have low fructosamine due to increased protein turnover rate. Hypoalbuminaemia in dogs can cause  false negative low fructosamine. 
  • Blood ketones may be increased and ketoacidosis may be present
  • Liver enzymes - often increased
  • Serum lipids - often increased trigycerides and cholesterol
  • Urea - usually normal, but can be slightly increased (to 20mmol/l) if there is dehydration and increased protein breakdown
  • Electrolytes - sodium, potassium, bicarbonate may all be low. 
  • Blood pH - low if ketoacidotic


  • Glycosuria occurs when the blood glucose concentrations exceed 8-11mmol/l and in diabetes mellitus on urine test strips glucose exceeds 2%.
  • Ketonuria - ketones should not be present in urine, but they are in about 50% of dogs with diabetes mellitus.
  • Specific Gravity - often normal.
  • Urine pH may be more acidic than usual if acidosis is present

For uncomplicated diabetes mellitus  treatment involves :

It is important to stabilise the animal then continue with precisely the same dose of insulin and feeding protocol. If you change the type of food, the amount, or the timing of feeding, OR if you change the dosage or timing of insulin administration  you can easily destabilise the patient. For this reason it must be stressed to owners that they must stick to the advice that their veterinarian gives .

Other reasons why stabilisation may be difficult include :

  • Your pet may develop an immunity to the type of insulin being used
  • Your pet may have more than one disorder at the same time, for example older animals often develop:
    • obesity
    • renal failure
    • heart failure
  • If insulin resistance cannot be overcome the condition will progress
  • Sometimes insulin treatment may appear to be ineffective - and there are a variety of causes of this CLICK HERE

Treatment of cases complicated by ketoacidosis involves :

  • Replacement fluids by intravenous route
  • Replacement electrolytes
  • Correct acid-base imbalance
  • Reduce blood glucose concentrations - soluble insulin I/V or I/M
  • Reduce blood ketones

If the diabetes is not stabilised,  the high circulating glucose concentrations lead to liver disease, and the animal may eventually go into a coma and die.

In cats which are prone to develop stress-induced hyperglycaemia fructosamine estimations have been recommended to aid in interpretation of high glucose concentrations.

Oral hypoglycaemic agents may be of use in the management of feline NIDDM (See Oral Hypoglycaemics clinical update )

Good for stabilised patients with controlled glycaemia. Guarded for cases with ketoacidosis

Long term problems
Sometimes insulin treatment may appear to be ineffective - and there are a variety of causes of this CLICK HERE


Update January 2016