• Medicine

Diabetes mellitus is a common endocrine condition of dogs and cats. It most commonly causes increased water consumption and urination and weight loss. Managed well, diabetic dogs can have a good quality of life.

Diabetes mellitus usually occurs in middle-aged to older dogs. Any breed can be affected but some are more predisposed than others. Signs associated with diabetes may include:

• Increased drinking

• Increased urinating

• Increased appetite

• Weight loss

• Dehydration

• Infections – urinary tract, skin, lungs

• Vomiting, diarrhoea, halitosis

• Lethargy

• Poor eyesight due to cataracts

Almost all dogs with diabetes require insulin for treatment. This is because the special beta cells in the pancreas do not produce enough insulin. The cause of this reduced insulin production has not been fully characterised in dogs. The activity of any insulin present can also be antagonised (inhibited) by a number of factors such as drugs (especially corticosteroids), obesity and other hormonal diseases like Cushing’s disease. Insulin is important because it is a molecule that acts like a key, allowing glucose to enter the cells of the body to be utilised for energy. Without insulin, the glucose sits in the blood stream and the cells of the body breakdown fats and other substrates to make energy, using processes that are much less efficient and that can be toxic.

Diagnostic tests

Other hormonal diseases can mimic diabetes, particularly Cushing’s disease. In order to diagnose diabetes and rule out other concurrent diseases, your vet will need to take a blood sample for analysis (CBC, biochemistry +/-T4 +/- blood gases). They will also need to collect a urine sample to check for glucose, ketones and infection. There can be a number of changes on the blood tests but the main feature is an increased glucose (which will also be present in the urine).

Often your pet can be quite well despite having diabetes, however sometimes they can become quite sick. These animals usually have a condition called diabetic ketoacidosis. This is diagnosed by finding ketones in the urine as well as glucose, as well as changes on the blood gas profile, which tell us that the patient is acidotic. This condition makes the animal unwell and usually reduces their appetite. If they have ketoacidosis, they usually require hospitalisation and intensive care initially. In most diabetics, especially those with ketoacidosis, it is important to rule out other concurrent diseases. Various screening tests may be performed, particularly chest Xrays (to rule out problems in the lungs or heart) and abdominal Xrays/ultrasound.

Treatment and monitoring

The most important aspect of treatment is owner commitment. This is a disease that we do not cure, but manage (with the exception of diabetes caused by medications and other disease, which may sometimes resolve if these factors are removed). Long-term treatment usually requires 12 hourly insulin injections and feeding, which cannot be missed. Regular monitoring is also important to make sure the patient is not getting too much or too little insulin. Therefore, there are ongoing costs (medications, blood tests, equipment +/- special diets) plus a significant time commitment. It is often useful to establish whether you will be able to organise another carer who is prepared to give injections in case you need to go away.

The mainstay of treatment is insulin, given twice daily as an injection under the skin, usually at the same time as meals. If the patient does not eat, then a reduced amount of insulin is usually given and if this continues for more than one meal, veterinary advice must be sought. There are a number of types of insulin used, and the choice is usually up to the prescribing vet. It is most important to make sure that the insulin is stored properly (usually refrigerated). Before use it usually needs to be mixed gently then drawn up into the syringe. The injection can be given in a number of places, including the scruff of the neck or the side of the chest. The skin is tented to form a triangle and the needle placed gently into the centre of the triangle to make sure it is given into the subcutaneous tissue. Sometimes it is hard to tell if you have got it in as you are usually administering small amounts and there is lots of fur. If you are having trouble, ask your vet to clip a small square of fur so you can see the skin.

Diet is another important factor in management of diabetes. There is a lot of debate about the type of diet that best facilitates good diabetic management. The most important thing is making sure your dog eats two equal meals morning and night, at the same time as insulin administration. The diet should ideally be a good quality commercial diet. Home-prepared meals are also an option but these must be discussed with your veterinarian so we can ensure that the diet meets your dog’s energy and nutritional requirements. Regular exercise is also important. It will help achieve or maintain a healthy weight and better glycaemic control. Excessive exercise however is probably not ideal.

As mentioned, your dog will require ongoing monitoring. The most common technique is a blood glucose curve, which usually requires hospitalisation for a day and serial blood glucose measurements. Sometimes these curves are used in conjunction with another blood test, fructosamine, which give us a further idea about the average blood glucose levels over the past month. The blood glucose curves will be done quite frequently, every 1-3 weeks initially, but over time the frequency may decrease to 3-6 monthly, depending on whether your dog is showing clinical signs.  Most recently, a new kind of monitor, which uses a small implant under the skin, has allowed us to continuously monitor the blood glucose of your pet over a few days in the comfort of their own home.

If your dog does have diabetic ketoacidosis, hospitalisation will almost definitely be required. In order to treat this condition, intravenous fluids and rehydration, intensive insulin therapy and monitoring as well as other more specific treatments, such as antibiotics, pain relief or alternative feeding techniques may be required. Hospitalisation may be required for one week or more, so the costs involved are greater. Once your dog is stabilised and eating again without any vomiting or diarrhoea, we change to the standard treatment approach above.

Complications of therapy can occur, particularly the development of diabetic cataracts, which can lead to blindness. These can be removed, which usually leads to a return of vision, as long as the retinas (back of the eye) are not affected by the diabetes.

Another complication is the risk of hypoglycaemia due to an insulin overdose (usually either due to too large a dose or not enough food intake). This can lead to seizures, weakness, shaking and disorientation. If this occurs and your dog is conscious and able to eat, feeding a meal may help. If they are unable to eat, glucose syrup or honey can be placed in the mouth and veterinary care should be sought immediately.


Diabetes mellitus is a disease that can be well managed long-term and many diabetic dogs lead a good quality of life for years.


Written by Dr Sophie Haynes

Image: Coco, one of our diabetic patients

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