How Diabetes Affects Dogs
There are two types of canine diabetes – diabetes insipidus and diabetes mellitus. Of these, diabetes mellitus – particularly Type 1 or insulin-dependent diabetes mellitus - is by far the most common. In healthy animals, insulin is produced and released by specialized cells in the pancreas. Insulin is needed for glucose from ingested food to pass into cells and tissues, where it can be processed and used for energy. Dogs with Type 1 diabetes mellitus do not have enough insulin in their blood streams, because their specialized pancreatic cells are either absent or not functioning normally. This prevents them from properly metabolizing dietary sugar, which in turn causes abnormally high blood sugar levels (hyperglycemia) and levels of glucose in their urine (glycosuria). Dogs with excess urinary glucose tend to excrete very large amounts of urine, leading to dehydration and unusual thirst.
The metabolic abnormalities associated with diabetes mellitus initially increase a dog’s appetite because its cells are unable to take in and use dietary sugars. This is called “going into starvation mode.” The dog’s body starts breaking down stored fat for energy. This causes certain acid byproducts of fat metabolism called “ketones” to build up in the blood. Ultimately, this can cause a very serious and life-threatening condition known as diabetic ketoacidosis.
Disruption of the complex metabolic system can lead to a number of different symptoms. While many of these are vague and non-specific, taken together they can suggest the presence of diabetes mellitus and may help owners and veterinarians arrive at an early diagnosis.
Symptoms of Diabetes in Dogs
Owners of dogs with diabetes mellitus may notice one or more of the following signs in their dogs:
- Increased thirst and water intake (polydipsia)
- Increased volume and frequency of urination (polyuria)
- Inappropriate urination (loss of house training; accidents in the house or car; incontinence)
- Increased appetite and excessive food intake (polyphagia)
- Weight loss despite increased food intake
- Dehydration (severe in end-stage disease)
- Difficulty breathing (slow, labored breathing)
- Abdominal pain
- Strong odor of acetone on the breath
- Urinary tract infections (from abnormally high glucose levels in the urine)
- Cloudy eyes; cataracts
- Vision abnormalities (acute onset of blindness caused by bilateral cataracts; fairly common in dogs)
- Exercise intolerance
- Loss of appetite (inappetence; anorexia; later in the course of disease)
- Poor body condition
- Poor skin and coat condition
- Disorientation; stupor
- Lack of coordination (ataxia)
- Seizures; convulsions
It may seem odd that many diabetic dogs noticeably lose weight early-on in the course of their disease, even though their appetites and food intake increase. However, this does happen.
In the long term, untreated affected dogs eventually will suffer from signs of progressive, systemic disease. A systemic illness is one that affects or involves multiple body organs or systems. Cataracts are common in diabetic dogs and often are what cause owners to visit the veterinarian in the first place. Liver enlargement (hepatomegaly) and neurological disorders are frequent consequences of untreated diabetes mellitus, and affected dogs are especially susceptible to infections. If a dog begins making frequent trips to the water bowl, urinates more (or more frequently) than usual and develops a ravenous appetite without gaining weight, a red flag should go up about potential diabetes mellitus.
Dogs at Increased Risk
Diabetes mellitus is seen in all breeds of dogs, including mixed breeds. However, it is most common in middle-aged and older obese females. Diabetes mellitus usually is diagnosed in dogs in the 4 to 14-year range, with the average age of onset being somewhere between 5 and 10 years. Diabetes mellitus can occur in young dogs, but that is the exception rather than the rule. Female dogs are affected 2 to 3 times as frequently as males. The reason for this gender association is not understood.
Type I diabetes mellitus an insulin-dependant form of the disease that appears to have a familial association, is more common in the Keeshond, certain Terriers (Australian, Fox, Cairn and Yorkshire), German Shepherd Dog, Doberman Pinscher, Schnauzer (Standard and Miniature), Golden Retriever, Labrador Retriever, Bichon Frise, Spitz, Poodle (Miniature, Standard and Toy), Samoyed, Pug and Lhasa Apso. The exact role of genetics in this disease is not well understood.
Risk factors other than breed and gender include obesity, recurring pancreatitis (normally presenting with signs of abdominal distress), being an older intact female, hyperadrenocorticism (Cushing’s disease) and administration of drugs which antagonize the effects of insulin, such as certain steroid medications.