Diabetes in Dogs

Diabetes in dogs, also known as canine diabetes mellitus (D.M), is a metabolic endocrine disorder that affects the dog’s ability to regulate blood sugar levels. Just like in humans, dogs can develop both Type 1 and Type 2 diabetes. While it is more common in older dogs, diabetes can occur at any age and in any breed. Females are affected twice as often as males, and incidence appears to be increased in certain small breeds such as poodles, dachshunds, cairn terriers and beagles. Obesity is the most common contributing factor along with genetic predisposition, certain medications or illnesses.

The primary cause of diabetes in dogs is the insufficient production or utilisation of insulin, a hormone responsible for controlling blood sugar levels. In Type 1 diabetes, the pancreas fails to produce enough insulin, while Type 2 diabetes is characterised by the dog’s inability to use insulin effectively. Type 1 is more commonly seen in dogs.

There are many reasons for reduced insulin production but the most common is destruction of the Islet cells responsible for insulin production. This can occur through immune destruction or from chronic inflamed pancreas or ‘pancreatitis’. Over time as the pancreatic tissues (both endocrine – Insulin enzyme and exocrine – digestive enzymes amylase and lipase) are damaged it is replaced by fibrous connective tissue and eventually the organ becomes dysfunctional.

Insulin resistance and secondary D.M. is most commonly caused by obesity in dogs. It can also be secondary to spontaneous hyperadrenocorticism (cushings) or after prolonged periods of glucocorticoid steroid treatment. More rarely, intact females can release growth hormone from mammary tissues leading to insulin resistance.

Insulin is released into the bloodstream to allow utilisation of glucose, the end-product of dietary carbohydrates, producing energy at a cellular level allowing function. In a diabetic state without insulin influence glucose is not uptaken by cells and is left in circulation. There is then an overload of blood glucose leading to systemic dysfunction. The body will begin metabolising fat stores to meet energy requirements which can lead to a state of ketosis, a saturation of ketones from fat metabolism.

Hyperglycaemia (excessive glucose in the blood) can lead to signs of Polyuria (excessive urination PU), Polydipsia (excessive drinking PD) and Polyphagia (excessive hunger) along with some other clinical signs.

• PUPD is the first clinical sign owners notice at home. We see an obvious increase in water intake and urination. Hyperglycemia causes the kidneys to excrete glucose via urination. Due to osmosis diuresis the glucose pulls water with it leading to excessive urine production with a knock-on effect of excessive thirst and water intake.
• Polyphagia is seen despite chronic weight loss. The food is not being metabolized at a cellular level so the fat stores are used for energy demands.
• Cataracts are often seen in undiagnosed cases of DM or as an eventual end result even while treated. Due to glucose saturation of the lens sorbitol is produced which is not readily diffused in the lens and leads to clouding and eventual loss of vision.
• A weakened immune system due to the DM leads to dogs being more prone to skin infections and urinary tract infections from normally harmless pathogens.
• Hepatomegaly (enlarged liver) is caused by excessive fat metabolism and accumulation in the liver.
• Diabetic KetoAcidosis (DKA) is the most worrying presentation of DM. Excessive fat metabolism causes ketone production. Ketones are strong acids and their accumulation leads to metabolic acidosis and illness.

Dogs will present with signs of vomiting, inappetence and lethargy.
Some dogs may have a sweet smelling breath/urine from acetone ketones excreted through the lungs and kidneys.
DKA left untreated can lead to organ damage and eventual death.

Diagnosing DM in dogs involves a series of tests, including blood and urine analysis to measure glucose levels. Once diagnosed, treatment typically involves insulin therapy, which involves regular injections of insulin to regulate blood sugar levels. Along with medication, dietary changes and regular exercise are crucial for managing diabetes in dogs.

Diagnosis involves full blood and urine testing. We measure the level of blood glucose which reflects current glucose levels, while a fructosamine test reflects the level of blood sugars in the preceding 6 weeks. Urine is tested for the presence of glucose and ketones. We test general organ function to ensure there are no primary or secondary complicating diseases. These tests can be performed relatively quickly and allow for treatment to begin.

DKA patients require hospitalization for IV fluid therapy while waiting for glucose and ketone levels to stabilize. It may take days before the animal is in a fit state to go home.
While in hospital we record a ‘glucose curve’ monitoring the blood glucose response to insulin injections.

Treatment is in the form of management not a cure when it comes to DM. Weight management, diet control, desexing female dogs and frequent monitoring can help manage the disease but we must supplement insulin to allow normal carbohydrate metabolism and clinical improvement.

Porcine Lente insulin is most commonly used for canine DM management. This is an intermediate acting insulin meaning it’s peak effect is 4 hours after injecting and weans by 12 hours. Thus generally we inject twice a day after meals.

When thinking about insulin therapy it’s essential to understand what we are doing on a cellular level. After a meal is digested we have a blood glucose peak. A non-diabetic patient then releases its own insulin to drive this glucose into the cells for metabolism and energy supply. We inject our diabetic patients with insulin to move this blood glucose into the cells.
With this in mind it’s essential our pet eats a meal before giving insulin. If we inject on an empty stomach there will be no blood glucose peak to act on but insulin will still cause a drop in blood glucose. This can lead to hypoglycemia, a concerning state of low blood sugar. This can also happen even after a meal if we give too high an insulin dose.
For this reason it is important for a glucose-curve to be made at initial diagnosis along with regular monitoring so we know what the ideal insulin dose is resulting in normoglycemic state after meals.

Signs of hypoglycemia to watch out for include;
Altered mentation and behaviors, tremors/twitching, weakness, collapse and seizures.
Seeks immediate veterinary attention if this occurs. At home you can rub glucose syrup or honey on the gums and give orally once your pet can swallow.

The key to successful management at home is a strict routine by feeding the same volume and type of food (ideally diabetic prescription kibble), at the same time of day while injecting the same volume of insulin. It is essential NOT to feed any food between the morning and evening meals, this would cause glucose peaking during the day without insulin influence causing instability.
We recommended owners to attempt monitoring at home with pet blood-glucose kits so they can track the trends themselves along with regular in-house clinic monitoring.

Within a week of starting therapy we should generally see improvement of clinical signs namely decreased drinking and urination and increased energy levels.

With proper management and veterinary care, dogs with diabetes can lead happy and fulfilling lives. It is important for dog owners to be vigilant for any signs of diabetes and work closely with their veterinarian to develop a comprehensive treatment plan tailored to their dog’s needs.