The growing diabetes epidemic is not limited to people—diabetes mellitus is increasing among dogs as well. Researchers estimate that one in 200 dogs will develop the disease. Fortunately, treatment has made huge strides in recent years, and as a result, dogs with diabetes are living longer, healthier lives.
The mechanism of diabetes is relatively simple to describe. Just as cars use gas for fuel, body cells run on a sugar called glucose. The body obtains glucose by breaking down carbohydrates in the diet. Cells then extract glucose from the blood with the help of insulin, a hormone made by the pancreas in specialized cells called beta cells. (The pancreas, an organ situated behind the stomach, produces several hormones.) In diabetes mellitus, cells don’t take in enough glucose, which then builds up in the blood. As a result, cells starve and organs bathed in sugary blood are damaged. Diabetes is not curable, but it is treatable; a dog with diabetes may live many happy years after diagnosis.
Kinds of Diabetes
Humans are subject to essentially three kinds of diabetes. By far the most common is Type 2, followed by Type 1 and gestational diabetes. Type 2 diabetes has typically been a disease of middle and old age (though it is being seen increasingly in young people), and has two causes: The beta cells don’t make enough insulin, or muscle cells resist insulin’s help and don’t take in enough glucose (or both). As a result, blood glucose levels climb. Type 1 diabetes usually occurs when the immune system attacks and destroys the beta cells, cutting off insulin production; the reason for this attack is thought to be a combination of genetic predisposition plus exposure to a trigger (research into possible triggers is ongoing). Glucose then stays in the blood and, again, levels skyrocket. Roughly half of people who have Type 1 diabetes develop it by age 20. Gestational diabetes starts during pregnancy and is probably caused by hormonal changes.
You may have heard that dogs generally get Type 1 diabetes, but the reality is more complicated. Though there are no universally accepted definitions of dog diabetes, the United Kingdom’s Royal Veterinary College identifies two forms: insulin-deficiency diabetes (IDD) and insulin-resistance diabetes (IRD). Neither matches any kind of human diabetes exactly.
In IDD, a dog loses beta cells and no longer makes enough insulin to keep glucose levels under control. Causes include genetic defects, inflammation of the pancreas and immune attack (as in human Type 1 diabetes). In IRD, something prevents the dog’s insulin from functioning properly. That “something” may be “diestrus,” pregnancy, an endocrine disease, or treatment with steroids or progesterone-like hormones. Diestrus, the most common cause of IRD, is the approximately two months of high levels of progesterone (a female hormone) between periods of estrus (heat). Hormonally, diestrus resembles pregnancy, making this form of IRD similar to human gestational diabetes.
Several factors raise a dog’s risk of developing diabetes. These include breed, age, gender, weight, diet, virus infections, an inflamed pancreas, chronic inflammation of the small bowel, Cushing’s disease (excess production of the hormone cortisol) and long-term use of progesterone-like drugs or steroid drugs.
•Breed. A study published in the Veterinary Journal in 2003 examined diabetes rates in thousands of American dogs and found that overall, mixed-breed dogs were more prone to diabetes than purebreds. Among purebreds, breeds varied greatly in their susceptibility.
•Age. Dogs most often develop diabetes during middle or old age.
•Gender. Female dogs and neutered male dogs are more likely than intact males to get diabetes.
•Weight. Obesity can make cells resistant to insulin, but it’s unclear whether it actually causes diabetes in dogs.
•Diet. A diet high in fat may contribute to pancreatitis (inflamed pancreas), a risk factor for diabetes.
Signs, Symptoms, Diagnosis
Diabetes can be a silent disease. Your veterinarian may discover your dog’s diabetes through routine bloodwork, but before that, you are likely to notice some of its symptoms: greater than normal hunger and/or thirst, weight loss, and frequent or copious urination (some dogs start having accidents in the house).
A blood test that measures your dog’s blood glucose level is the most common diagnostic tool, but a high glucose level does not always mean diabetes. Because other diseases sometimes raise these levels, your vet may run additional tests to rule out such causes.
Once your dog is diagnosed, her veterinarian will obtain a “serial blood glucose–concentration curve” by measuring her glucose level repeatedly over many hours. The results will help the vet choose an appropriate insulin, dose and dosing schedule.
After treatment starts, your dog will need to be routinely tested to see how well the protocol is working. Most commonly, either a fructosamine test or a glycated hemoglobin test, which reveal average control over the previous one to three weeks (fructosamine) or two to four months (glycated hemoglobin) is used. In contrast, the daily blood glucose measurement is a snapshot, an indication of your dog’s glucose level at one specific moment.
In the long run, the label your vet gives your dog’s diabetes isn’t important. A good treatment plan is what matters. Treating diabetes is as much an art as a science. The goal of treatment is to keep blood glucose levels close to normal—roughly between 65 and 120 mg/dl—so that your dog feels good now and is less likely to develop diabetes-related problems later. The most common diabetic complication in dogs is cataracts (clouding of the lens of the eye); over time, dogs may also develop hardening of the arteries, kidney disease, retina disease or nerve disease. And because bacteria thrive on a high-sugar diet, dogs with diabetes are prone to gum, urinary, skin and other infections. Other components of treatment include proper diet, weight loss (if your dog is overweight), an exercise program and home testing of blood glucose levels.
•Insulin. With rare exceptions, dogs with diabetes need one to two daily insulin shots to survive; the insulin is injected just under the skin. Your vet may prescribe a human insulin, or possibly Vetsulin, which is a purified pig insulin; Vetsulin is the only insulin approved for use in dogs in the U.S. Insulins vary greatly in how quickly they start working, when their action peaks, how long they last and how much they cost. Your vet will take these factors into account when choosing the best type for your dog.
•Home monitoring. Weigh your diabetic dog regularly and watch for signs of excess hunger, excess thirst and excess urination, indicators that her glucose levels may be too high. Regular testing of your dog’s blood glucose level can reveal problems before they become emergencies. Glucose levels rise after meals, occasionally when your dog is sick, and when the insulin dose is too low or timed improperly; they drop during fasting, after exercise, and when the insulin dose is too high or timed improperly. Both too-high and too-low levels can be dangerous.
Testing also lets you know how well the treatment program is working.“It’s extremely important that a clear understanding be developed of the meaning of blood glucose monitoring,” says William D. Schall, DVM, professor in the Veterinary Medical Center at Michigan State University in East Lansing. When interpreting the results, consider when your dog last ate, how much exercise she has had recently, when she received an insulin dose, how large the dose was and any symptoms.
Testing involves pricking a hairless area with a lancet, collecting the blood drop that wells up and using a small device called a blood glucose meter to measure the concentration of glucose in the sample. Many dog owners use human blood glucose meters. However, these meters tend to read low for dogs. The AlphaTRAK meter is designed for dogs and cats and requires only a tiny blood sample. “Whichever glucose meter is used, the results should be compared at some point to the results obtained by the veterinarian’s laboratory by performing simultaneous samples,” says Louise Murray, DVM, DACVIM, director of medicine at the American Society for the Prevention of Cruelty to Animals in New York City.
When your dog is sick, the vet will also want you to test your dog’s urine for ketones (a poisonous byproduct of fat breakdown); you may need to do that on a regular basis as well.
•Diet. Researchers are still exploring what diet is best for dogs with diabetes. Most veterinarians recommend a diet low in fat and high in fiber. Fiber slows the entrance of glucose into the blood and may satisfy your dog’s appetite sooner, so she eats less and loses weight. Your veterinarian may recommend a prescription dog food designed for dogs with diabetes, or a homemade diet developed by a veterinary nutritionist. Some dogs may refuse to eat special diets; in that event, careful choices should be made when selecting a regular dog food. The one food Dr. Schall absolutely advises against for diabetic dogs is the semi-moist type that comes in packets. “They generally contain more refined carbohydrates than other dog foods,” he says.
•Exercise. Exercise not only may help reduce your dog’s weight, it also lowers blood glucose levels. Your dog should exercise every day for about the same length of time at about the same exertion level. Consistency is important—an unusually long or vigorous exercise session can cause blood glucose levels to drop dangerously low.
•Weight loss. If a dog is overweight, shedding some pounds can make the cells more sensitive to insulin, which means that glucose uptake is easier.
•Spaying. Spaying prevents female dogs from going through diestrus.
Day to Day With Your Diabetic Dog
Keeping a logbook can help you monitor your diabetic dog’s progress. Every day, record blood glucose test results; any ketone test results; changes in your dog’s appetite, weight, appearance, water intake, urination frequency or mood; and any treatment changes your veterinarian makes. A simple notebook, calendar or computer spreadsheet works well.
Among the things to watch for on a day-to-day basis are hyperglycemia, when blood glucose levels rise above the top end of the recommended normal level (ask your vet what this is for your dog; since perfect control isn’t always attainable with current methods, vets generally try to keep most dogs below 200 mg/dl), and hypoglycemia, when the level drops to 60 mg/dl or less.
Hyperglycemia can lead to ketoacidosis (harmful levels of ketones in the blood), which qualifies as an emergency, and you should call your vet right away. Symptoms include drinking lots of water, urinating frequently or copiously, loss of appetite, weakness, vomiting, lethargy, ketones in the urine, or—in the most serious situation—coma. Test strips are available to detect ketones in your dog’s urine, and you should report the presence of ketones to your veterinarian immediately, even if your dog has no other symptoms.
In hypoglycemia, a range of symptoms may be present, including restlessness, lethargy, confusion, weakness, wobbliness, lack of coordination, shivering, sweaty paws, seizures or coma. Test your dog’s blood glucose level if these symptoms appear. If it is below the recommended level, rub maple syrup, Karo syrup or tube cake frosting—high-sugar foods that are quickly absorbed into the bloodstream—on your dog’s gums and the inside of her cheek, then call your vet to report the episode and get further instructions.
Modern medicine has made caring for a diabetic dog quite doable and certainly worthwhile. Although daily care can seem burdensome at first, once you get used to it, it becomes a routine part of the day, like feeding her or taking her for walks. Owners do not need to worry that shots and blood tests will take over their lives. Nor do they need to fear that their dog will not be happy. According to Dr. Schall, almost all diabetic dogs can be treated at home and can enjoy a good life. A diagnosis of diabetes offers a challenge, but it’s a challenge that can be successfully met.