Canine Diabetes Mellitus
Your 8 year old dog has started drink a ton of water. He’s also beginning to pee in the house. A lot. You
begin to wonder, “Maybe if I don’t let him drink so much, he will stop peeing in the house.” But this
could be the road to disaster. What you need to be thinking is, “I need to take my dog to the vet to find
out what’s wrong.”
There are many reasons a dog will drink more and urinate more. Your veterinarian will need to run a
comprehensive blood panel and a urinalysis to determine the cause of the problem in your dog. One of
the more common diseases that causes increase thirst and urination is diabetes mellitus.
Diabetes occurs when the pancreas stops producing insulin. Insulin regulates the level of glucose (a
basic sugar) in the dog’s bloodstream and allows the dog’s cells to absorb the glucose to use as energy.
When the dog does not have enough insulin, the blood glucose rises, but it can't get into the dog’s cells.
So what happens next? First, the excess glucose overwhelms the kidneys and is dumped into the urine.
The glucose in the urinary bladder draws extra water in along with it, creating vast amounts of urine.
The dog who is losing all this water in the urine feels dehydrated and starts to drink more. If you limit
this dog’s water, he will continue to urinate excessively and thus become extremely dehydrated and
very sick. He needs this extra water to survive.
The next thing that happens in the diabetic dog is he starts to break down his body’s proteins and fats so
that his cells can get the energy they need. This results in a marked weight loss. These dogs often have
increased appetites because they feel like their bodies are starving.
How is diabetes diagnosed? Both the blood and the urine samples that your vet evaluates will have high
levels of glucose. A normal glucose level is about 100 mg/dL. Diabetic dogs often have glucose levels
over 400 mg/dL. If your dog’s glucose levels are only moderately elevated, your vet might want to check
a fructosamine level. This test will show the average level of glucose in the bloodstream over the past
two weeks, and may help confirm the diagnosis of diabetes.
The good news about diabetes is that, while it can’t be cured, it is a treatable condition. Your vet will
teach you how to give injections of insulin to your dog. The needles are tiny and the dogs hardly seem
to mind. The injections typically need to be given twice daily, and it is critical that the dose is precise.
Too much insulin can be even worse than too little. For this reason, your vet will typically start your dog
on a relatively low dose of insulin, knowing that it will probably need to be increased.
A few weeks after you start giving these insulin injections, your dog will spend a day at your vet’s
hospital for a test called a glucose curve. This is where your vet will take a tiny sample of your dog’s
blood every two hours to determine how low his blood glucose gets as well as the highest level it gets.
The ideal glucose curve has a low point of about 150 mg/dL and a high point of about 250 mg/dL. If your
dog’s glucose is too low at any point in the curve, your vet will decrease his insulin dose, just as he will
increase the dose if the glucose is too high. Curves are repeated every two or so weeks until the dog is
regulated, meaning the levels are at the point where the signs and problems associated with diabetes
are minimal.
Some diabetic dogs can be difficult to regulate. There are several reasons for this. Other hormones can
affect glucose levels. Intact female diabetics should be spayed as soon as your veterinarian feels this is
safe to do, so that the fluctuating progesterone levels associated with heat cycles don’t wreak havoc
with your dog’s glucose levels. Cushing’s Disease is another hormonal problem. It is a condition where
the dog creates too much of the hormone, cortisone, in his body, also making glucose levels difficult to
control. Likewise, the administration of cortisone in the form of pills (like prednisone) will affect glucose
levels and you should avoid giving them to diabetic dogs when possible. Veterinarians typically
recommend high fiber diets for the hard to control diabetic as they seem to keep glucose levels from
getting too high or too low. It is also helpful that your dog gets the same level of exercise every day, as
increases in activity can increase the dog’s need for insulin.
So what’s the big deal with diabetes? Do I really have to treat it or can I just give my dog more food and
let him outside more to pee? Diabetes, when not controlled, can lead to a condition called diabetic
ketoacidosis, which is life threatening. As the body breaks down fat to use for energy, another type of
fuel is formed called ketone bodies. Your veterinarian can test for and detect ketone bodies in your
dog's urine. As the ketones are burned for fuel, the dog’s pH and electrolyte balances are disturbed and
the dog becomes extremely ill. He will stop eating and act depressed. He will usually vomit and may
even stop drinking and become dehydrated. If not treated immediately (ideally in a 24 hour care
facility), he will die. It is imperative that you have your dog checked at the first symptoms of diabetes.
There are other, less severe complications associated with diabetes in the dog. Cataract formation in
the eye is common in diabetic dogs. Excess glucose in the blood can be absorbed into the lens of the
eye and is converted into another sugar called sorbitol. The sorbitol pulls water into the lens and
creates a cataract, leading to blindness. Diabetic dogs are also prone to repeated urinary tract infections
because the excess glucose in the dog’s bladder makes it an ideal place for bacteria to grow. It is
important to monitor your diabetic dog for signs of infection. Signs of infection include: straining to
urinate, urinating small drops at a time, blood in the urine, or unusually bad odor to the urine. For
diabetics, veterinarians often send urine samples for culture and sensitivity tests on a regular basis to
check for infections.
So what if my diabetic dog is regulated and doing well? Why does my vet want me to come back in for
another glucose curve? Most veterinarians recommend that diabetic dogs have glucose curves done
every three to six months. This is because over time, your dog’s metabolism may change. His insulin
requirements may increase or decrease. If he is drinking more, you can probably guess that he needs
more insulin. But even if he seems to be doing well, his blood glucose may actually be getting too low.
If his blood sugar is moderately low, your dog will feel fine. But if it continues to decrease, your dog will
begin to feel lightheaded, dizzy and weak. If the glucose drops even lower, your dog can have seizures
or go into a coma. If you even think this may be happening you should give your dog some Karo syrup
and get him to a vet immediately. If he can’t swallow, you can rub the syrup into his gums. It would be
much better to routinely check a glucose curve to know if your dog needed to decrease his dose of
insulin, than to wait until he became critically ill.
Why do dogs get diabetes? Can I prevent it? While diabetes in cats is similar to Type 2 diabetes in
humans and can often be avoided with proper diet and weight control, diabetes in dogs is similar to
Type 1 diabetes (or insulin dependent diabetes) in people. There is believed to be a genetic
predisposition to the condition, and there is currently no known way to avoid it. Nobody knows what
triggers development of the disease, but it does seem more prevalent in obese dogs. There are
currently no genetic tests for diabetes.
Long term success in treating diabetes is possible and is largely dependent on the owner. Care of the
diabetic dog requires careful monitoring of the dog’s condition, consistency with dosing and timing of
insulin injections, and maintaining a regular diet and exercise regime. While it is never fun to have
health issues with your dog, with proper care and early diagnosis, the diabetic dog can live a long, happy
life.