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Diabetes in Dogs - Causes & Treatment

A significant number of diseases that dogs and cats get are unique to those species, which is why you take your dog to the vet not to your local GP. However, there are others that are similar to the diseases that humans get. Diabetes is one of these diseases.

There are many different causes of diabetes in dogs, but almost all require treatment in a similar fashion. Diabetes (or Diabetes mellitus, to give its full name) is a failure of the regulation of sugar in the bloodstream

There is another form of diabetes called Diabetes insipidus which is caused by an upset in the adrenal gland. For this article, we shall refer to Diabetes mellitus as “Diabetes”.

Which dogs are most at risk?

Diabetes tends to affect middle-aged dogs, mostly about 6-10 years old, though it can be seen in younger and older dogs. 

Female dogs are about twice as likely to be affected as males, and it is more common in un-desexed dogs. Certain breeds are more susceptible. We see many cases in Poodles, Cairn Terriers, Dachshunds, Beagles and Cocker Spaniels.

What happens when a dog has Diabetes?

In a healthy dog, there is a hormone called insulin, which is made in a gland near the stomach called the pancreas. This hormone is a facilitator of blood sugar use and transport. The pancreas makes insulin on demand, and the insulin helps the blood sugar “glucose” to pass out of the blood stream and into cells all over the body giving those cells the energy they need to function. 

Active cells call out for more energy, the liver releases more glucose, more insulin is produced and the glucose moves into the cells where it powers the cell functions. This is all part of the wonder of life that goes on inside our bodies every hour of every day.

When a dog develops diabetes, there is insufficient insulin around
so glucose cannot pass into the cells, so the cells run out of energy. The cells call out for more energy, the liver responds and releases more glucose into the bloodstream, but as the lack of insulin means glucose cannot get into the cells to nourish them, the cells call out again for more energy. 

The liver responds and speeds up its release of glucose, often breaking down stored energy in a rather haphazard way trying to satisfy the cells’ demands, which still cannot be met as the all-important insulin is not present.

As a result, the cells run out of energy, the liver works overtime breaking down energy stores and releases ever larger amounts of glucose into the bloodstream. This high level of blood glucose is of no use to the cells without insulin to help it enter the cells. The very high blood glucose level overloads the kidneys spilling over into the urine, dragging water with it into the urine. The energy depleted cells make the dog feel tired and hungry. The haphazardly broken down energy stores makes the dog lose weight. The excessive glucose level, and the extra water dragged with it, in the urine, makes the dog urinate more, and so it wants to drink more to replace the water lost as it urinates.

So now we can see what signs we might expect in a dog with diabetes. A typical diabetic dog is hungry but despite its increased appetite it loses weight

It is thirsty and it urinates a lot. It might have accidents on the floor, and these puddles are often quite sticky and are attractive to ants because of the high level of glucose in the urine.

What are the likely causes of diabetes?

Some dogs can develop diabetes due to a so-called “auto-immune reaction, where the dog’s own body defence system,  - its immune system - attacks and destroys the pancreas. Mostly however, diabetes in dogs is due to one of two other types of disease. Either the pancreas makes insufficient insulin, or the cells in the body cease being able to respond to the insulin (“insulin resistance”).

#1. Reduced Insulin Production

The pancreas can become damaged in a variety of different ways, all leading to reduced insulin production. The pancreas is a very fragile organ and it can be damaged by infection and by inflammation

Repeated bouts of pancreatitis (inflammation of the pancreas) can wipe out the insulin producing cells, as would most pancreatic cancers. One of our dogs, a Cocker Spaniel, was a real garbage guts. We had some long renovations at home and she sought out the fatty chicken carcasses that our less than tidy tradies would leave lying around, despite our repeated pleas for them to use the bins. She had several bouts of pancreatitis and later in life developed diabetes.

Some hormones made naturally in the body are antagonistic to insulin production. Typically the hormones released around the time a bitch is on heat will affect insulin secretion. All the hormones in the body are interdependent, and other conditions like an underactive thyroid and overactive adrenal glands (“Cushings disease”) can affect insulin secretion.

As vets we have a fantastic array of medications we use every day. Our training makes us well aware that wonderful though these drugs may be, the same drugs almost invariably have side effects. Over the years, my clients have often asked me for more of the wonderful blue (or green, or white) pills to stop their dog scratching. Whilst they do indeed stop a lot of itches, repeated doses of cortisone can lead to the development of diabetes.

#2. Insulin Resistance

A common cause of insulin resistance is obesity

Overfeeding a dog can not only lead to a variety of mobility problems, and reduced quality of life and reduced longevity, but obesity and a continually high blood glucose level stops the cells from responding to insulin. They cannot absorb the energy and so the glucose demand-oversupply cycle gets going, leading to diabetes. 

It such a tragedy when an owner comes to us with a fat dog that has diabetes and we have to explain that the obesity may be an owner induced malady. Other diseases can also lead to insulin resistance.

Diagnosis of Diabetes

In the early stages of diabetes, there are few signs to warn us that anything is wrong. Over time, more clues become evident. Sometimes diabetes can develop very quickly, other times it is more insidious. 

Many owners assume that their dog is just getting a bit slower, less enthusiastic about walks and is losing weight because it is older. The hunger and thirst may pass unnoticed

Some dogs are presented because they have gone blind suddenly, with bright white centers to the lens in one or both eyes. These cataracts are quite common in diabetic dogs. 

When we are suspicious of diabetes, we will perform a thorough clinical examination and will always try to get blood and urine samples at the same time, looking for high levels of glucose in both. 

A single high blood glucose level does not necessarily indicate diabetes. False diagnoses can occur if the dog has just eaten or if it is very stressed. If in doubt, there is a blood test for “fructosamine” that shows that a dog has had sustained high blood glucose levels. Our suspicions may also be raised if a dog has had repeated infections, or a history of other diseases. 

Treatment of Diabetes

So, what can be done if a dog has diabetes? Firstly we confirm the diagnosis. At this point, I run through everything above with the dog owners. I explain that we all have amazing bodies, which try every day and every meal to even out the excesses that we throw at them.

When we eat a big meal we get a spike in blood glucose and all the internal mechanisms in our bodies do their best to sort it all out. When we exercise our cells make demands on our bodies for energy. When a pet has diabetes, however, a lot of this fine internal balancing is lost. So as vets and pet owners, we have to try to balance things out.

Most diabetes in dogs is caused by insufficient insulin and so we have to supply more insulin. This means injecting our pets, usually twice a day. In 36 years, I have only ever had one dog owner who could not face injecting her dog. It does take a bit of getting used to, but we encourage you to practice injecting oranges and bananas to get the technique! 

In essence, the insulin we inject has to match up with the food the dog eats. So regular measured feeds are paired with regular measured insulin. It will take several days for your vet to work out the correct dose of insulin for your dog. 

We work out a starting dose on a dose per kilogram basis, and then refine it to get the desired blood glucose level. This will be a dose for your dog and for a particular feeding strategy for your dog. No two diabetic dogs are identical. Each dose of insulin will cause a reduction in the blood glucose level. 

It is really important to ensure your dog is eating adequately. If you inject a dog with insulin and it has not eaten, then it is possible to lower the blood glucose level too much and the dog has a “hypo” crisis which can be fatal. So, if in doubt as to whether your dog has eaten the Golden Rule is: DO NOT INJECT!

Your vet will also advise you to exercise your dog, and will suggest ongoing weight loss if it is obese. Once more, regularity of exercise and weight reduction is critical to the successful management of the diabetes. Avoid sudden changes, without close consultation with your vet.


Diabetes is a relatively common condition in dogs. It can be successfully managed, but this will require close cooperation between dog, owner and vet. 

You will have to adhere to regular feeding and insulin injection schedules. However, it you are committed to the process, there is every chance that your dog will live out its life happily and healthily. 

Inca (left) is on insulin and a regular diet and still loves to run all day chasing balls.
In terms of prevention, keep your dog active and slim – oh!, and make those tradies put their chicken carcasses in the bin, every time...

written by Dr. Gordon Heslop (2016) for Australian Dog Lover (all rights reserved).

About the writer

Dr Gordon Heslop (Bachelor of Veterinary Medicine. Member of the Royal College of Veterinary Surgeons. B.Vet. Med., M.R.C.V.S.) qualified as a Vet from the Royal Veterinary College and after five years in practice in the UK he migrated to Australia. He now owns two veterinary hospitals in Sydney. Gordon has special interests in surgery and medicine in dogs and cats, and also in communicating veterinary matters to pet owners. He is a great believer in demystifying science, making it understandable to dog and cat owners. 

He was the resident Vet on the Channel 10 morning TV show. 

Gordon has been a vet for over 35 years, and happily embraces every day at work and all the new challenges that each day brings. 

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