Diabetes Mellitus, a somewhat common hormonal disturbance in dogs and cats, occurs due to either a lack of insulin production or the development of insulin resistance. The majority of diabetic dogs have Type 1 Diabetes, meaning they are insulin-dependent.

While all dogs and cats are susceptible to diabetes, certain dog breeds appear to be predisposed. These include the Schnauzer, Bichon Frise, Miniature Poodle and Maltese.

Because diabetes affects so many pets, it’s important to know the causes (especially those that are preventable) and the clinical signs. Further, I encourage pet owners to understand the diagnosis process, treatment options and associated risks.

Causes and Clinical Signs of Diabetes Mellitus

Causes of Insulin Deficiency
  • Destruction of insulin-producing cells from pancreatitis
  • Autoimmune destruction of insulin-producing cells
  • Lack of insulin-producing cells at birth (rare)
Common Causes of Insulin Resistance
  • Pancreatitis
  • Hyperadrenocorticism (Cushing’s syndrome, i.e. too much steroid production)
  • Urinary tract infections
  • Pregnancy
  • Hormones from being a non-spayed female
  • Acromegaly (cats)
  • Certain medications (e.g. steroids)
  • Obesity
  • Other concurrent disease
Clinical Signs and Consequences of Diabetes Mellitus in Dogs and Cats
  • Excessive appetite, thirst and/or urination
  • Weight loss
  • Cataract formation (ALL dogs will develop cataracts secondary to diabetes if given enough time)
  • Weakness in the hindlimbs/wobbliness in walk (i.e. diabetic neuropathy; more common in cats)
  • Enlarged liver


If your veterinarian suspects your dog or cat has diabetes, he or she will test blood glucose and urine glucose levels because repeatedly high blood glucose with glucose in the urine is diagnostic for diabetes mellitus. However, your veterinarian may perform other diagnostics (such as full blood chemistry, complete blood count, blood gas analysis, urinalysis, urine culture, abdominal ultrasound, and others). In doing so, he or she is looking for evidence of the aforementioned causes of insulin resistance and evaluating for diabetic ketoacidosis (DKA).

Treatment of Diabetes Mellitus

The mainstay of diabetic management is insulin therapy. While there are numerous types of insulin, not every insulin type works for every animal. Upon diagnosis, your pet will need to see a veterinarian frequently (perhaps every two weeks) for the first few months. Your vet will adjust the insulin dose to most appropriately manage your pet’s glucose levels. Unfortunately, diabetes mellitus is almost always a lifelong disease and your pet will require insulin injections every day.

Additionally, obese animals must lose weight. Some veterinarians recommend diets low in carbohydrates (which are broken down into sugars) or high in fiber. Though this is not incorrect, the most important thing to me is that the animal eats a balanced diet and that all treatments, diets, exercises, and daily routines remain consistent. Consistency is the biggest key to successful treatment of diabetes mellitus.


There are numerous ways to monitor the efficacy of your pet’s insulin treatment, including:

  • Blood glucose curves: blood draws at set intervals over a period of time (commonly 10-12 hours) to measure blood glucose
  • Urine glucose curves: similar to blood glucose curve, but performed on urine
  • Fructosamine: essentially a single blood draw that gives an average of glycemic control over the previous two weeks
  • Continuous glucose monitor: patch placed on your pet’s skin that continuously downloads data for a more comprehensive study over a two-week period

While there are pros and cons to each method, I prefer the continuous glucose monitor for a few reasons. First, this technique minimizes the patient’s stress because once the patch is adhered to the shaved area of skin, the pet can go about his or her day as normal. And second, the procedure only takes a matter of minutes. It goes without saying that we don’t want our pets to experience stress, but it’s particularly important to keep them relaxed while monitoring blood sugar. Stress falsely elevates glucose levels.

Complications of Poor Diabetic Control

If managed appropriately, most dogs with diabetes mellitus will maintain a good quality of life and can live for multiple years after diagnosis. However, there are severe consequences when the disease is poorly regulated. Risks include:

  • Low blood glucose from overdose can cause lethargy, depression or even seizures
  • Diabetic ketoacidosis (DKA) from lack of therapy or insulin underdose is life-threatening and requires intensive monitoring and treatment
  • Continued weight loss, inappropriate urination and excessive appetite

Therefore, it is extremely important to keep a close relationship with your primary veterinarian or veterinary internist to ensure your pet’s diabetes is being controlled.


If your pet is diagnosed with diabetes mellitus and requires advanced medical care, ask your primary vet for a referral to one of our Internal Medicine specialists.

Want to receive monthly notifications when we post on our blog? Subscribe here.