Diabetes mellitus is on the rise among cats in the United States, according to a survey of clinics nationwide — an increase that has been correlated with a rise in obesity. Although it’s hard to draw definitive conclusions from the results of the survey, there’s no question that feline weight control is a key to preventing this chronic disease.
According to Orla Mahony, MVB, a specialist in small animal endocrinology at Cummings School of Veterinary Medicine at Tufts University, “I have concerns about over-interpreting the results of any survey without having sufficient data to explore. We don’t know that the incidence [of diabetes mellitus] has actually increased, or if there is simply better recording and monitoring, or more testing.” But, she cautions, “There’s no question that you want to prevent your cat from getting fat to avoid the disease.”
Understanding Diabetes Mellitus in Cats
Diabetes mellitus is characterized by the body’s inability to produce or to utilize insulin, a hormone that allows glucose (sugar) to enter cells and be converted to energy. When the disease isn’t controlled, glucose and fats remain in the blood, eventually damaging vital organs. [As in most non-technical articles, the term “diabetes” here refers to diabetes mellitus.]
There are two main categories of diabetes in humans. Type 1 is, in essence, an autoimmune disease that causes the body to attack and destroy insulin-producing beta cells in the pancreas. It’s manageable with injections of insulin, but it’s not reversible.
In the much more common type 2, typically seen in overweight adults and, increasingly, among obese children, the pancreas still produces insulin, but either it does not produce enough or the body is resistant to the insulin it does produce. If it hasn’t progressed to a dangerous stage, type 2 diabetes can often be controlled by diet and oral medications.
Type 2 is the variety to which cats are usually subject, but by the time most cats are diagnosed, the disease is fairly advanced. This means that they are likely to be insulin dependent for the rest of their lives, according to Dr. Mahony, who is board certified by both the American and European Colleges of Veterinary Internal Medicine.
Common Causes of Diabetes in Cats
Many of the same factors that come into play in human diabetes cause feline diabetes too: obesity, inappropriate diet and insufficient exercise.
Melissa Freer of Eagan Minnesota first noticed signs of diabetes in her cat, Sebastian, after he had put on weight. “I started traveling on business more and I let my two cats eat from a cat feeder while I was away,” she says.
One of her cats, Nick, just ate until he was full, but Sebastian loved his food and ate excessively. Freer says, “I didn’t realize until he was already overweight that he would just sit in front of the feeder and binge.”
But just as recent research points to the possibility of a genetic basis for a predisposition towards obesity and diabetes in humans, a small-scale study in the United Kingdom suggested that this may also be the case for cats.
According to Dr. Mahony, the researchers identified a genetic mutation that was more likely to turn up in domestic short-haired cats with diabetes than in those who didn’t have the disease.
“Up until now, we were more interested in a cat’s lifestyle issues, that the cat was obese,” she says. “This was the first time the role of genetics was studied.”
Steroids Can Cause Insulin Resistance in Cats
An extended use of steroids or cortisone-type drugs can also cause insulin resistance in cats. Dr. Mahony says, “We warn owners of any cat who we have on long-term steroids that diabetes is a risk, and we try to monitor carefully to make sure that doesn’t happen.”
Chronic pancreatitis and other endocrine diseases, such as acromegaly and Cushing’s disease, are considered to be contributing factors to diabetes, too. Obesity, however, is the major contributing factor for most diabetic cats. And neutering may increase the risk that a cat will become obese.
“I tell clients, the moment they neuter their animal, the diet begins right there,” she says. Although she recommends neutering for other reasons, including population control, Dr. Mahony adds, “It is a double whammy. You have a lower metabolic rate and an increased appetite.”
Common Diabetes Symptoms in Cats
The most prominent early signs of feline diabetes are an increase in drinking and urination. Since animals with diabetes lose weight and muscle mass — the body is breaking down stores of fat and protein in an attempt to create glucose — a cat suffering from this condition may become weak. Cats are particularly prone to a disorder known as neuropathy, which causes weakness in the back legs. In fact, it’s this symptom that often alerts owners to the fact that there is a problem.
Other warning signs that may be exhibited by a diabetic cat include lethargy, depression and an unkempt coat. Problems with the coat are not a well-recognized sign, but it was the sole indicator for Freer that something was wrong with her cat, Sebastian.
“He started getting clumped fur near the base of his tail and getting dandruff,” says Freer. “I couldn’t figure out what was wrong.”
Freer’s veterinarian confirmed that Sebastian was diabetic. “Sebastian never displayed any other signs of diabetes — no increased urination or weight loss,” Freer says.
Often, the most difficult — and costliest — phase of caring for a diabetic cat occurs right after diagnosis. Getting blood glucose levels stabilized is a complex process that involves finding the correct type and dose of insulin to administer. Cats metabolize insulin more quickly than dogs or humans, so the longer-acting insulins known as PZI (ProZinc) and Lantus are usually the most effective for them.
At minimum, you can expect your cat to spend several days in a veterinarian’s office or specialist’s clinic getting glucose curves — blood tests conducted over 12 or 24 hours that measure the amounts of glucose in the blood and chart the times at which those amounts peak and dip. To complement these tests and to spot-check blood glucose levels, Dr. Mahony recommends home testing.
Diabetes Treatment and Maintenance for Cats
Most cats need to have insulin shots twice daily. As with humans, cats must eat before getting the shots in order to prevent severe hypoglycemia (dangerously low blood sugar). So once the correct dose of insulin is established, it’s important to keep glucose levels on an even keel by feeding the same amount of food at the same time each day.
It’s also ideal to get your cat slimmed down. “If you are determined enough, you could probably do it,” Dr. Mahony says, “but it can be very difficult to get a diabetic cat to lose weight.”
For one thing, she notes, “Clients are now being told they have to feed their cats twice a day because otherwise their glucose might dip. You’re trying to get your cat to eat while being concerned about her weight.”
It’s also difficult to get diabetic cats to exercise because they’re generally middle aged or older by the time the disease is diagnosed. “You can try to get them to move around more, but it’s not that easy,” Dr. Mahony says.
Diets prove similarly challenging. “Low-carbohydrate diets are a helpful development in feline diabetes,” Dr. Mahony says. “But it’s difficult to find feline-balanced diets that are both low carb and low fat. They either tend to be weight-control diets, which are lower fat and higher carbs — or low carb, which are not geared towards weight control.”
If she had to choose, Dr. Mahony says, she would opt for the low carb, ideally the canned rather than the dry versions, which are lower in calories. “Those diets do help,” she says. It is unusual, however, for a cat to have a reversal of diabetes as a result of diet alone.
“At Tufts, we may get 10 percent of cats off insulin,” Dr. Mahony says. “Most of our cats require insulin and a proper diet for good control.”
Some studies do suggest a high rate of success for getting cats into complete remission with diet alone, she notes, adding that the remission rate may depend on the specific population of cats. But Dr. Mahony says that you’d have to recognize the disease very quickly for diet alone to be effective.
Giving Insulin Shots to Cats
The good news: Giving insulin shots is not difficult. Most cats don’t even notice the injections and, once the cat is regulated, giving them becomes very routine for owners.
“People seem to think giving shots is complicated, but it’s not as hard as you think,” Freer says. “Sebastian never seemed to care. He never complained and never ran away from the shots.”
Nor was there any effect on his quality of life — or on Freer’s. Freer had her sister give Sebastian the shots when she had to travel. Sebastian was diagnosed at age seven and lived another nine years.
“Sebastian was never sick until he was old,” Freer says. “And I never thought of him as a diabetic cat. He was a great cat who happened to have diabetes.”