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.

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.

• Increased thirst (over 100ml/kg/day)
• Increased urination
• Dehydration (mild)
• Weight loss - Animals that develop diabetes are often overweight initially - but because the tissues can not use the blood glucose  for energy, they breakdown their own body fats stores and protein to make energy...so animals with diabetes often lose weight during the illness.
• Increased appetite
• Hepatomegaly (50% of cases)
• Cataracts

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

Complications
Liver involvement is secondary to the diabetic state. 

• Normal blood glucose reference range for dogs is 3.5-6.1 mmol/l (63.1-109.9 mg/dl) In diabetes mellitus fasting blood glucose concentrations exceed 8.5mmol/l for at least 8 hours after a meal.  (NB Cats get stress-induced hyperglycaemia in which blood concentrations may reach 8.5-12.5mmol/l and this should not be confused for diabetes).
• Glucose tolerance test - used to determine if a mild hyperglycaemia is significant or not. 1g glucose /kg body weight is given intravenously as a 40-50% solution over 30 seconds. Whole blood samples are collected into fluoride/oxalate tubes before and after collection and at regular intervals. In diabetic dogs the blood glucose concentrations fall much slower than they do in normal dogs.
• Fructosamine and glycosylated haemoglobin are glycolated proteins that act as markers of mean glucose . 
  • GHb is not affected by stress (so is especially useful in cats) or post-prandial hyperglycaemia and gives an indication of glucose concentrations over the previous 2-3 months. This test can be affected by anaemia, or polycythaemia.. NB erythrocytes survive 68 (cats) - 110 days (dogs) so changes in GHb will not occur quickly.
  • Fructosamine gives an indication of glucose levels over a 2-3 week period.  Fructosamine concentrations are approximately :

	Fructosamine values (micromol/l)
Dogs
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+
Cats
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+

• 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

Urinalysis

• 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

• Regular insulin injections if the animal has IDDM.. The aim is to give sufficient insulin to maintain urine glucose concentrations between 0.1-0.5%. This indicates that the renal threshold is just exceeded by circulating blood concentrations
• Reduce body weight if obese - high fibre diets are often low-calorie rations as well so are beneficial for the control of glucose digestion and absorption as well
• Treatment of  any underlying cause - treating heart failure may reduce catecholamine release (eg adrenaline) and so reduce peripheral insulin resistance  
• Dietary management. Some diets are much better for diabetics than others. For example, high fibre diets are usually recommended nowadays because they help to control the rate of sugar digestion and absorption into the body following a meal. Your veterinarian will advise on the best food for your pet.

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 )

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