Disease and Illnesses of dogs – Diabetes

What is Diabetes?

Diabetes or Diabetes mellitus to give it its full name occurs when there is a lack of the hormone insulin in the body. Insulin controls blood

sugar levels, specifically glucose so when there is lack of insulin, blood glucose levels are not controlled properly.

Insulin is produced in the pancreas and Diabetes occurs either when the pancreas is not producing enough insulin or if the tissues of the body are insensitive to the insulin. Sometimes underlying conditions are present which can cause this so called ‘insulin resistance’. Other hormone disorders such as Cushing’s disease and drugs such as progesterone and steroids can contribute to this problem.

Diabetes most often affects middle ages to older dogs and appears to be more common in female dogs compared to male dogs and especially entire (non neutered) female dogs.

In an unaffected dog, when blood glucose levels start to rise, after a meal for instance, insulin will be produced and this causes the glucose to be taken up by cells in the body and used as a source of energy, hence lowering the levels of glucose in the blood. In diabetic dogs, this insulin release is not effective so the blood glucose levels remain high. This glucose is not available to the body to use as energy so the body starts using other sources of energy such as breaking down fat. 

Diabetes affects approximately 1 in 500 dogs but can usually be managed well once it has been diagnosed. Treatment has to be tailored to each individual dog and some are easier to stabilise than others but once the diabetes is controlled then the affected dogs can live happily for many years.

 What are the symptoms of Diabetes?

Dogs with Diabetes often seem fairly well in themselves and the most common symptoms you are likely to see are:

·      Increased thirst (polydipsia)

·      Increased volume and frequency of urination (polyuria).

When dogs have high blood glucose levels, some of this glucose leaks into the urine and this glucose in the urine drags more water out with it which leads to the increase urination. The increased thirst is to make up for all the fluid lost in the urine.

·      Increased appetite (polyphagia)

·      Weight loss despite the increased appetite

This is because although a lot of food is going in, the sugars in it cannot be used for the energy due to the lack of insulin so the body starts breaking down fat as described above and this leads to the weight loss.

More occasional symptoms that you may see are

·      Recurrent infections, especially bladder infections as the excess sugar in the blood and urine is an ideal breeding ground for bacteria.

·      Cataracts. The excess sugars present in the lens draw in water and this moisture causes the lens to lose its normally clear appearance and become opaque. These can be treated by surgical removal of the lens.

In more severe or prolonged cases of poorly controlled diabetes, the body starts producing a substance called ketones and when these build up in the system they can cause a more severe consequence of the disease called Diabetic Ketoacidosis. Dogs with Diabetic ketoacidosis are very unwell and can have symptoms ranging from weakness to vomiting and diarrhoea to collapse. This is an emergency situation and needs to be seen by a vet as soon as possible.

 How is Diabetes diagnosed in dogs?

Your vet is likely to be suspicious of Diabetes from the history and clinical examination but the symptoms are not unique to Diabetes so further testing is needed to get a definitive diagnosis. This will usually involve blood and urine testing initially.

The blood glucose levels are checked and if they are high then the vet will be very suspicious of Diabetes in your dog but further testing is needed to make sure. The next step is to measure a compound called Fructosamine. Fructosamine shows what level the blood glucose has been over the previous 2-3 weeks so this proves that high blood glucose levels are persistent and not just a one off and therefore confirms diabetes.

The urine is checked for glucose as if blood levels are high, glucose leaks into the urine as described above. Urine is also tested for ketones so as to be aware of and hopefully prevent potential Diabetic ketoacidosis, also described above.

 How is Diabetes treated?

Diabetes is managed rather than treated as treatment is often needed lifelong once a diagnosis has been made and diabetes cannot be cured.

Firstly, if there are any complicating factors such as another disease process going on or weight issues then these need to be dealt with first in order to be able to stabilise the Diabetes. Your vet is also likely to recommend spaying your dog if they are an entire female as this will remove the effect of hormones such as progesterone and make it easier to stabilise the diabetes. It is also really important to have a set routine as far as exercise and food are concerned so that each day is the same. More on this below.


Weight is really important as this can be a risk factor for developing diabetes in the first place as being overweight causes insulin resistance. If this is proving difficult then your vet can offer advice and sometimes a special diet food will be needed such as Hills r\d or Royal Canin obesity diet.

 Even if your dog is not overweight when diagnosed with Diabetes, diet can play an important role in controlling the disease. There are prescription diets that have been specially formulated to help control diabetes such as Hills w/d and Royal Canin Diabetic. These diets have low levels of slow release carbohydrate to help give a steady blood glucose level rather than a sharp increase that can be seen after a meal. They are also good for controlling weight.

 When feeding a Diabetic dog it is important that meals are evenly distributed with the same amount being given each day at the same times. The total daily ration is ideally split into 2 equal fractions and fed morning an night, 12 hours apart or close to that. This really helps to stabilise the Diabetes as the dose of insulin given is the same each day so ideally the food needs to be too. If one day your dog eats twice as much as normal then the insulin dose will not be enough that day. Equally if they only eat half their normal food, the insulin dose may be too much.


This is the most common form of treatment for Diabetes and although it may sound daunting initially, injecting your dog is usually quite easy and stress free and often easier than giving a tablet. Your vet should give you a chance to practice injecting, sometimes into a model and sometimes with your own pet but using water initially to practice.

 Diabetic dogs are usually started on a standard starting dose of insulin and then the response to this insulin is monitored. The dose is then adjusted as needed and then the blood glucose levels are rechecked. This process is repeated until your vet is happy with the control of the blood glucose and your pet seems well. Ongoing monitoring of diabetes is explained further below.

 There are several different types of insulin and the exact type of insulin required by your dog will be decided by your vet. Do take care with storage of your pet’s insulin as it will often need to be refrigerated and some need to be agitated gently before use. Ask your vet about the specific storage of your insulin.

 Some are given by once daily injection and some are twice daily injection, usually in the scruff of the neck. The needles used for these injections are very fine so they are not painful for your dog. Some forms of insulin will be injected with a traditional needle and syringe but some now come with an insulin pen which is loaded with a cartridge of insulin and disposable needles and you dial up the prescribed dose and the pen injects the correct amount. The needles you use will need to be disposed of safely so your vet should also supply you with a ‘sharps bin’ in which to place used needles. These are then sealed and returned to your vet for disposal.

 Insulin Overdose:  If you accidentally inject your dog with too much insulin OR if you inject the insulin and then your pet either doesn’t eat or vomits up their meal then there is likely to be too much insulin in the system. If you think this might be the case then call your vet for advice straight away. Too much insulin can push the blood glucose too LOW and this is called a hypoglycaemia episode or Hypo for short. This can cause weakness and seizures and can be an emergency so contact your vet immediately if you see these signs in your dog.

 How do we monitor our dogs Diabetes?

The vet will want to keep a very close eye on your dog after starting treatment for diabetes because, as we’ve mentioned already, both very high and very low glucose can be a problem.

Regular blood tests will be needed both to check glucose and fructosamine as mentioned above. The exact frequency of these blood tests will be decided by your vet and will depend on how your dog is responding to treatment. Sometimes your vet may want to hospitalise your dog for the day so they can check the blood glucose every couple of hours, often after a dose change. This is called a blood glucose curve. You may even be able to do this at home yourself with a portable blood glucose monitor specially calibrated for animals that you may be able to purchase through your vet.

Urine testing is also helpful and this can be done by putting test strips into the urine to measure glucose. If the blood glucose levels are normal then there won’t be glucose in the urine, if levels are a little high still then some glucose may leak into the urine.

The exact monitoring protocol put in place for your dog will be decided upon by you and your vet and will depend on how your dog’s diabetes is progressing, how amenable they are to testing and how much you are happy and able to do at home.

Return to index