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Diabetes mellitus in dogs: A vet's guide

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Like humans, diabetes mellitus in dogs is a disease that is characterized by increased levels of blood glucose due to insulin deficiency or resistance. 

Consistency is key in terms of treatment for all types of diabetes in dogs. This includes both diet (buying the best diabetic dog treats for instance), and exercise when managing this lifelong condition. Keep reading to learn more about diabetes mellitus in dogs including the causes, symptoms, risks and effective treatments of this condition.

What is diabetes mellitus? 

Diabetes mellitus is a chronic metabolic disorder that affects approximately 1 in 300 dogs. In this condition, hyperglycemia (increased blood glucose) occurs due to insulin deficiency or resistance.

The most common type of diabetes mellitus in dogs is insulin deficiency diabetes (“type I”), where the beta cells of the pancreas are absent or dysfunctional, usually due to immune-mediated destruction or pancreatitis. 

Beta cells produce insulin, which is required for glucose transportation into the tissues, so this type of diabetes results in low insulin levels, leading to hyperglycemia and “starved” tissues. The body subsequently breaks down muscle and adipose tissues into proteins and fats, respectively, to convert into energy sources in a process called gluconeogenesis.

In rare cases, obese dogs can develop insulin resistance diabetes (“type II”), where insulin receptors on the cells are less responsive to insulin. Dogs can also develop a third type of diabetes in which insulin resistance occurs due to increases in other hormones during pregnancy or from certain tumors.

What causes diabetes mellitus in dogs? 

Although no exact cause of diabetes mellitus has been identified, several risk factors have been reported:

  • Breed Certain breeds have higher rates of diabetes, including Poodles, Miniature Schnauzers, Samoyeds, Keeshonds, and some terriers, among others
  • Age Diabetes is most frequently diagnosed in middle-aged dogs 
  • Female sex Intact female dogs have an increased risk of diabetes due to high progesterone levels between heat cycles. Entire female dogs with diabetes should be spayed once they are stable
  • Obesity Obesity contributes to insulin resistance and increases the risk of pancreatitis
  • Pancreatitis Chronic pancreatitis can result in the loss of pancreatic endocrine tissue, including beta cells
  • Increased glucocorticoids Increased glucocorticoids (a type of steroid) in the blood due to steroid treatment or Cushing’s disease can antagonize insulin
  • Hormone-secreting tumors Tumors such as pituitary adenomas and pheochromocytomas can secrete hormones that counteract insulin. 

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Symptoms of diabetes mellitus in dogs

The most common symptoms of diabetes mellitus in dogs include:

  • Increased urinations, due to glucose in the urine taking additional water with it 
  • Increased thirst, due to fluid loss from excessive urination
  • Increased appetite, due to the cells being starved of glucose  
  • Weight loss, due to the breakdown of muscle and fat tissues for energy 

How is diabetes mellitus diagnosed in dogs? 

The diagnosis of diabetes mellitus in dogs is made based on clinical symptoms, elevated fasting blood glucose levels, and the presence of glucose in the urine. The presence of ketones in the blood or urine supports this diagnosis.

Your vet may wish to perform additional diagnostic tests to confirm the diagnosis, rule out other conditions, or determine if there are additional diseases present. Many dogs diagnosed with diabetes mellitus only show increased thirst and urinations, which is seen in other conditions including (but not limited to) kidney disease, liver disease, Cushing’s disease, and some cancers.

How is diabetes mellitus treated in dogs? 

The treatment of diabetes mellitus in dogs involves twice-daily insulin injections under the skin at mealtimes to promote glucose uptake. This can seem daunting to many dog owners, but most dogs tolerate their injections well once they are used to their routine. Each dog will respond differently to insulin, so it may take some time to determine their ideal dose and type of insulin.

Diet is another important aspect of treatment. Diabetic prescription diets are available, which typically contain good-quality protein and are high in fiber and complex carbohydrates. However, it is crucial that a diabetic dog’s food is palatable enough that they will eat it consistently, even if this means they are not fed a prescription diet.

The key to successful management of diabetes is a consistent routine in terms of insulin administration, diet, and exercise to minimize abnormal fluctuations in blood glucose. Insulin injections, meals, and walks should be at the same time each day. Some dogs may also require additional small meals or treats between injections to avoid hypoglycemic episodes, which can be discussed with their vet.

Owners must be aware of the time and financial commitments required to care for a diabetic dog. Dogs with diabetes require consistent, lifelong treatment and frequent monitoring. Additionally, some dogs may require hospitalization for complications, which can be costly.

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What are the complications of diabetes mellitus in dogs? 

Some complications of diabetes mellitus in dogs include:

  1. Urinary tract infections  Bladder infections are very common in diabetic dogs due to the presence of glucose in the urine, which attracts and feeds bacteria
  2. Cataracts  High blood glucose levels cause sorbitol, a sugar, to accumulate in the lens, which subsequently draws water into the eye, giving it a cloudy appearance 
  3. Hypoglycemic episodes  When a diabetic dog is given too much insulin, doesn’t eat enough, or does too much exercise, they can become hypoglycemic. This can cause anxiety, tremors, incoordination, collapse, convulsions/seizures, coma, and even death. Dogs showing any of these signs should be taken to a veterinarian immediately. Owners should also keep oral glucose gel on hand in case their dog shows any signs of hypoglycemia. 
  4. Diabetic ketoacidosis  Diabetic ketoacidosis is a life-threatening condition that can occur if a dog’s diabetes is untreated or treated insufficiently. It happens when ketones produced during gluconeogenesis accumulate in the bloodstream, causing electrolyte imbalances and metabolic acidosis. This results in symptoms including vomiting, inappetence, lethargy, and collapse. This condition requires immediate veterinary attention and hospitalization, often for several days. 

Can diabetes mellitus be cured in dogs? 

 There is no cure for diabetes mellitus in dogs. Luckily, most dogs with controlled diabetes experience few symptoms and have a good quality of life. For this reason, diabetic dogs can still live long, happy lives if their owners are willing and able to commit to lifelong treatment. 

Dr. Diana Hasler graduated with distinction from the University of Edinburgh Royal (Dick) School of Veterinary Studies in 2018. She has experience working as a small animal veterinarian in general practice, where she has treated many dogs, cats, rabbits, and rodents. She has also recently branched out into the field of medical communications, doing freelance work as a medical editor and writer. Dr. Hasler currently lives in Edinburgh where she enjoys spending time with her husband Gavin and playing with their feisty tabby cat Poppy.