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 is an endocrine disease that 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 and retinal disease
Almost all dogs with diabetes require insulin for treatment. This is because the beta cells in the pancreas do not produce enough insulin. The cause of this reduced insulin production has not been fully characterised in dogs but is thought to be due to an auto-immune attack on the beta cells (just like type 1 diabetes in humans).
The activity of insulin can also be antagonised (inhibited) by a number of factors such as drugs (especially corticosteroids), obesity, inflammation, infection and hormonal diseases, such as Cushing’s disease (hyperadrenocorticism).
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 instead, using processes that are much less efficient and produce toxic byproducts.
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 significantly increased glucose levels in the blood (which will also be present in the urine).
Often your pet can be quite bright and relatively well despite having diabetes, but they can become quite sick with time. These animals usually have a condition called diabetic ketoacidosis. This is diagnosed by finding ketones in the urine and blood, 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 with the lungs or heart) and abdominal Xrays/ultrasound.
Treatment and monitoring
Diabetes mellitus is a disease that in most cases we cannot cure. Instead it has to be managed for the rest of the life of the pet.
The mainstay of treatment is insulin, most commonly administered as an injection under the skin, usually at the same time as meals. There are many types of insulin on the market these days, and the choice is usually up to the prescribing vet, who will discuss what best suits your pet based on their eating habits and lifestyle. Many formulations are given twice a day but some newer insulin formulations may work when given once a day.
Regular monitoring is also important to make sure the patient is getting an appropriate amount of insulin. Therefore, there are ongoing costs (medications, blood tests, equipment +/- special diets) plus a significant time commitment for the owner. It is often useful to establish whether you will be able to organise another carer who is prepared to give injections in case you are not at home or need to go away.
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. An insulin pen can also be used. 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 because 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 in dogs. The most important thing is making sure your dog eats, ideally around 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.
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.
As mentioned, your dog will require ongoing monitoring. At CARE we frequently use continuous interstitial glucose monitoring technology (CGM), in the form of a sensor applied to the skin, which then transmits glucose readings via Bluetooth to a phone or reader. This allows us to monitor your pet’s glucose levels in real time and make adjustments to the insulin dose without repeated hospital visits. Alternatively, a blood glucose curve can be performed, 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 gives us a further idea about the average blood glucose levels over the past month.
If your dog does have diabetic ketoacidosis, hospitalisation will almost definitely be required initially. 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. Cataracts can be removed by a specialist opthamologist, 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.
Prognosis
Diabetes mellitus is a disease that can be well managed long-term and many diabetic dogs lead a good quality of life for years.
Additional resources
Diabetes Mellitus: Introduction – Veterinary Partner – VIN
Written by Dr Sophie Haynes
Image: Coco, one of our diabetic patients