An Introduction of Diabetes Mellitus for Dog & Cat Owners

Dr. Gary Edelson, DVM

My cat, Oreo, has been drinking a lot of water and losing weight.  My veterinarian diagnosed diabetes, but what does this mean?

Diabetes mellitus is one of the most common endocrine diseases of dogs and cats. To better understand the disease process, lets review normal metabolism of an animal. The body’s cells need energy in form of glucose, a sugar, which is delivered by the bloodstream. Unless a hormone, insulin, is present, the body cannot absorb the glucose to use as energy. The pancreas, an organ that is located next to the stomach and small intestine, produces insulin into the bloodstream to regulate blood sugar. In addition to secreting insulin, the pancreas secretes digestive enzymes into the small intestine to aid in digestion.  

Insulin, acts like a key to unlock the cell so glucose can enter the cell from the blood.  Inside the cell, glucose is either used for energy or stored for future use in the form of glycogen. Without the key (insulin) to unlock the cell, glucose builds up in the bloodstream resulting in too much glucose (hyperglycemia) in the blood causing problems. When the glucose is about double the normal value in the blood, the kidneys cannot process it properly and the level increases in the urine (glucosuria). Glucose in the urine leads to increased production of urine (polyuria) as water is drawn out with the glucose and consequently more water consumption (polydypsia) results. In addition, an increased appetite results as the sugar present in their blood cannot be utilized without being unlocked by the key, insulin. As time goes on, the body uses protein, starch and fat for energy. When diabetes is left undiagnosed, ketones, a waste product, accumulates leading to vomiting, dehydration and depression. The disease can ultimately progress to coma and death if untreated.

Diabetes mellitus is a classic disease in humans and has been classified into two main forms: type I (juvenile, insulin dependant) and type II (adult, non-insulin dependant). With type I diabetes, there is no insulin (key) production by the pancreas.  Type II diabetes, the shape of the lock and key is different so even though the insulin is present, it cannot be utilized.  Nearly all dogs have type I diabetes, whereas their feline counterparts are mostly type II diabetic.

The cause of diabetes in dogs and cats is multifactorial. In dogs, there maybe a genetic predisposition where German Shepherd dogs, Schnauzers, Beagles and Poodles have an increased risk. Golden Retrievers and Keeshonds are most predisposed to developing juvenile diabetes. Middle aged (6-9 years old), female dogs are more likely to develop diabetes.  In contrast, male cats that have been neutered (fixed) over 6 years old are predisposed.

The four main clinical signs of diabetes are excessive drinking, urinating, eating and increased weight loss despite an increased appetite. If any of the signs above are recognized in your four-legged friend, contact your veterinarian as it maybe a sign of a serious illness.

Please consult your veterinarian before making any changes to your furry friend’s diabetes management.


Dr. Gary Edelson

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