Diabetes Mellitus

Diabetes mellitus is a condition caused by a lack of insulin or a lack of response to insulin. It is characterised by increased hunger, thirst, urination and weight loss. Similar to humans, diabetes mellitus is a commonly diagnosed condition in dogs and cats.

The food we eat is used for energy. Food must be broken down by the body to provide glucose (sugar) which is the fuel for cells. Glucose is needed by cells to perform their normal functions. Glucose normally circulates in the bloodstream ready to be taken up by cells as they need it. Insulin is a hormone made in the pancreas and is released when blood glucose rises after a meal as nutrition is absorbed from digested food. Insulin helps glucose move into cells. Without insulin, many cells of the body cannot use the glucose for energy even though the blood glucose levels may be high. The body then starts to breakdown fat and muscle to use as an alternate energy source resulting in weight loss.

Insulin is normally produced by specialised cells of the pancreas and is released into the bloodstream as glucose levels rise after a meal. In certain situations, either the pancreas stops producing insulin (known as type 1 diabetes) or the cells of the body become somewhat resistant to its effects (known as insulin resistance or type 2 diabetes). Dogs most commonly are type 1 diabetics and cats are most commonly type 2.

The classic symptoms of diabetes mellitus are increased hunger, thirst, urination and weight loss. Animals that develop ketoacidosis, a dangerous complication associated with poor blood glucose control, can become very unwell and usually have reduced appetite and vomiting.






Diabetes mellitus is diagnosed based on clinical symptoms, blood and urine tests demonstrating persistent high blood glucose and glucose being lost in the urine. Additional tests are required to determine if there are other complicating problems occurring. These may include further blood and urine tests, x-rays, and ultrasound. Other problems that are common in diabetic patients include urinary tract infections and pancreatitis.

The best treatment for diabetic dogs and cats is twice daily injections of insulin. Unfortunately, dogs and cats do not respond well to the tablets that some human diabetics use to control blood glucose, so insulin injections are necessary. If your pet has developed diabetic ketoacidosis (DKA) they usually require hospitalisation with intensive care as this is a life-threatening condition. To treat DKA your animal may need to temporarily receive a special type of insulin intravenously, close monitoring of their blood glucose and electrolytes, and treatment of concurrent medical problems.

Insulin is normally given as an injection under the skin. It can be a daunting prospect for some owners, but most people quickly become proficient and most animals tolerate the injections very well. The insulin injection is usually given in the region of the back of the neck or shoulder area. Usually the patient is not aware they are receiving an injection, especially if they are distracted when it is given, for example when eating a meal. Some owners find it easier if to begin with if we clip a patch of hair, so they can see the needle going under the skin. Moving the injection site is recommended to decrease scar tissue forming under the skin over time. Insulin can be administered with a syringe or using an insulin pen. More information on insulin administration using either syringes or pens can be found in the videos below.

Insulin is usually given as twice daily injections (given 12 hours apart) with meals. Meal feeding is important in dogs. Cats may graze if they prefer rather than eating meals at specific times. Your animal should be eating before insulin is given. Administering insulin to an animal that won’t eat might result in low blood glucose so if your animal is not eating check with your vet.

Several different types of insulin can be used to treat diabetic dogs and cats, including both human and veterinary insulins. It is very important to know which type of insulin your pet has been prescribed as the syringes used to give insulin are different. If the wrong type of syringe is used with a given insulin, it can cause a significant overdose or under dose. This is because veterinary insulins are generally less concentrated than human insulins. Caninsulin is a commonly used veterinary insulin and should only be used with veterinary insulin syringes. These have U40 written on the side of the syringes and are purchased at veterinary clinics. Human insulin (such as Lantas, Humalin, or Levemir) are more concentrated and should only be used with human insulin syringes, which have U100 written on the side of the syringe. You should always know which type of syringe your pet's insulin requires (U40 or U100) and ensure these are the only syringes used. If you are unsure, talk to your veterinarian.

A change in diet may be suggested to help improve diabetic control. A low carbohydrate diet that is high in protein has been shown to help glucose control in cats. There are some prescription diets made especially for diabetic cats. There is less evidence for a special diet in diabetic dogs. Depending on their other medical conditions, a lower fat, higher fibre diet may be recommended. Food high in sugar should be avoided.

It is important for dogs that their diet is consistent, such as the same type of food and volume is fed each day. Frequently changing the diet can make diabetic stabilisation very difficult. Always speak to your veterinarian before making changes to your diabetic pet's diet and exercise plan.

Monitoring your pet at home is important for not only establishing the ideal treatment for them, but also ensuring that their treatment remains adequate. Monitoring your pet means keeping an eye on:

  • Water intake (volume - approximately how much do they drink each day?)
  • Body weight (weekly weigh-ins may be helpful, as well as monitoring body condition)
  • Appetite (do they finish each meal and/or consume the same amount over the course of the day if allowed to graze?)
  • Checking urine for ketones and glucose (you can purchase ketodiastix from human pharmacies).
    NOTE: If your pet's urine dipstick results show no glucose or is positive for ketones, please call your vet for advice.

Keeping a weekly diary of body weight, appetite and water intake can be very useful to assess diabetic control and is relatively easy for most owners to do. Noting changes can help catch problems early and help us look at trends over time. In some animals more detailed monitoring at home may be needed. We may send your pet home with a Freestyle Libre sensor and scanner to check glucose levels or even discuss taking blood glucose samples at home if you are comfortable doing so (see videos below for more information on the use of Freestyle Libre sensors)

VSS - Diabeties

Regular rechecks are required for diabetic pets to ensure they are continuing to receive appropriate therapy. Recheck visits are normally scheduled every few weeks to begin with if your pet has just been newly diagnosed. This allows their insulin dosing to be adjusted to their individual needs and ensures your pet's glucose levels are adequately controlled. It is not unusual for changes to insulin doses or even insulin types to be made while the right treatment is found for your pet.

After adequate control is achieved (stable body weight, normal appetite and water intake) we may only need to see your pet periodically - usually every 3 to 6 months.

There may be times when your pet may need an in-hospital glucose curve performed to assess their response to their insulin dose. To do this, we usually have you feed your pet and give insulin as normal at home. Your pet is then admitted into our hospital where we take a small sample of blood every 2 hours over the day to monitor their blood glucose levels as it responds to their insulin dose. Stress affects this test so we usually cannot do any other procedures on this day and try and keep stress to a minimum. We may alter the insulin dose based on the results of this test and the information you give us on how your pet is doing at home.

Diabetes may predispose pets to other complications. It is important to recognise abnormal behaviour in your pet and to monitor their thirst, urination, hunger and body weight. Potential problems with diabetics include:

  • Cataracts (dog) - progressive blindness due to developing cloudy deposits in the lens of the eyes - almost all dogs with diabetes will develop cataracts within months of becoming a diabetic. This usually slowly results in blindness. Cataracts can in most cases be removed but many diabetics cope well with blindness. Cats do not tend to develop cataracts.
  • Persistent symptoms of diabetes (urinating and drinking more, increased hunger, weight loss)
  • Ketoacidosis - decrease in the pH level of the blood due to accumulation of dangerous levels of ketones, an alternative energy source for cells in the body when they can't get enough glucose (sugar) to operate normally. Signs may include lethargy, inappetence, and vomiting. Pets may be more likely to develop diabetic ketoacidosis if they are not receiving adequate amounts of insulin.
  • Hypoglycaemia - low blood sugar levels that can result in changes to behaviour such as stumbling, 'drunken' appearance, or even seizures. Accidentally giving too much insulin, either through inadvertent double dosing or if animals are given too much insulin when they are off their food, can result in low blood sugar levels which can become life-threatening if severe. Always seek veterinary advice if your pet skips more than one meal, has persistent vomiting or if they start to show signs of hypoglycaemia.

Most pets with diabetes live full and happy lives. Management of diabetic animals requires a team approach. There is no doubt successful management of diabetes in dogs and cats requires a significant commitment from the pet owner and a good relationship with the treating veterinarian.

If you have any questions, please contact our Internal Medicine team at Veterinary Specialist Services for more information on the management of diabetes mellitus in dogs and cats.


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