Cat Diabetes: Symptoms, Diagnosis, Treatment

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Senior orange tabby-and-white cat looking up next to a food bowl

Cats with diabetes have too much glucose (sugar) circulating in their bloodstream because their bodies aren't able to make insulin (Type 1 diabetes) or their cells don't respond to insulin (Type 2 diabetes). Type 2 diabetes is the most common form of cat diabetes.

Insulin is a hormone that allows glucose to be taken up by cells from the bloodstream and allows it to be stored in various forms. When there isn't enough insulin or the body doesn't respond to insulin, too much glucose remains in the bloodstream. 

When glucose is at normal levels in the bloodstream, the kidneys are able to reabsorb it so that glucose isn't found in the urine. In a diabetic animal, the kidneys aren't able to reabsorb all the extra glucose, and the glucose is spilled into the urine. The glucose in the urine pulls more fluid with it, so the cat produces more urine, which results in fluid loss and creates thirst in the cat.

Learn more about cat diabetes, including the symptoms and diagnosis, the potential causes of both Type 1 and Type 2 feline diabetes, and treatment methods.

Cat diabetes symptoms

The most common cat diabetes symptom is an increase in thirst and urine. Other common signs include an increase in appetite and weight loss. In fact, increased appetite can be an early sign of diabetes in cats. The cat’s cells aren't able to use the glucose in circulation, so they send signals to the brain that create an increase in hunger. But as the disease progresses, many cats actually lose their appetite because of a series of secondary effects on the body.

Weight loss happens because the cat isn't absorbing nutrients. Insulin also helps with the building of proteins, so not having or not being able to use insulin results in less protein production and less muscle mass.

Additional common signs of feline diabetes include dehydration, weakness, a rough hair coat, a distended abdomen, and a plantigrade posture (i.e., the cat’s ankles are low to the ground).

Diagnosing feline diabetes

As soon as any potential signs of cat diabetes are noticed, the cat should be taken to a veterinarian. If the cat is eating and seems mentally normal, it is not typically necessary to go immediately to an emergency clinic. However, things can change relatively quickly with diabetic cats, so it is not advisable to wait several days.

Even though there are classic signs of diabetes, other diseases can act the same way and be mistaken for diabetes in cats. Kidney disease, an overactive thyroid gland, liver disease, and urinary tract infections can all have similar presenting signs and look the same outwardly to the veterinarian. So to actually diagnose diabetes, the veterinarian will have to perform blood tests and a urinalysis. The blood will show an elevated glucose level, and the urine will have glucose in it.

Feline diabetes cannot be diagnosed simply on an elevated blood glucose because a cat’s glucose level can go up significantly due to stress. The trip to the veterinarian’s office and the drawing of blood can be enough to increase a cat’s blood glucose level. However, the glucose typically does not spill into the urine with such a quick spike. That’s why to diagnose diabetes in cats, both a blood test and a urinalysis are needed.

There is another blood test that can be used to determine whether a cat’s blood glucose has been elevated for longer than the time period of the stressful event. This test measures a cat’s level of fructosamine, a protein that has glucose attached to it, and it can give the vet an idea of what a cat’s blood sugar has been over the past one to two weeks. It can be used to confirm a diagnosis of diabetes, but it's more commonly used when obtaining a urine sample is not possible. Some cats come to the veterinary office with an empty bladder, empty their bladder on the way to the office, or just won't allow a sample to be taken.

Causes of Type 1 and Type 2 cat diabetes

There often isn’t one direct cause of diabetes. It is more appropriate to talk about which factors predispose a cat to develop diabetes. The biggest factor under our control is a cat’s weight. Overweight cats secrete too much of some hormones and not enough of others, causing the body not to respond as well to insulin.

Feeding a high-carbohydrate diet can also predispose a cat to becoming diabetic. Cats are obligate carnivores, and their metabolism is geared toward a diet that’s high in protein and low in carbohydrates. Eating too many carbohydrates leads to chronically elevated blood glucose levels, which can lead eventually to lower insulin secretion and cause glucose levels to go even higher. A low-carbohydrate diet is more easily achieved with canned food rather than kibble. (Note: Contrary to some popular misconceptions, canned food has not been shown to lead to worse dental health for cats.)

Other diseases that are untreated can also predispose a cat to diabetes. An overactive adrenal gland, an overactive thyroid gland, a chronically inflamed pancreas, and acromegaly (a condition in which the pituitary gland produces too much growth hormone) can all contribute to a cat becoming diabetic. In addition, male cats are more likely than female cats to be diabetic.

Treatment for diabetic cats

The mainstay of diabetes treatment in cats is insulin therapy. Insulin injections are typically given twice daily, though some cats do well on once-daily injections. The injections are given under the skin. Many people have concerns about giving injections to their cat. But with rare exceptions cats tolerate the injections well, and even the most needle-phobic person can be able to administer the injections.

Types of insulin

There are many types of insulin available. The one to use to treat cat diabetes is often determined by the veterinarian’s comfort level with a particular insulin, the availability of different insulins, and cost. Vets have their preferences based on what their experience has been, how they were taught, and what insulins are available in their area.

Glargine (Lantus) insulin is often the recommended insulin for newly diagnosed, uncomplicated cases of diabetes in cats. It is thought that cats have the greatest chance of going into remission (i.e., they no longer need insulin therapy) if they are started out using Lantus insulin. One drawback is that this insulin is quite expensive. However, the fact that cats have the greatest chance of going into remission with this insulin might make it the most economical choice because it’s possible that the cat won't need to keep getting the insulin and going through the recommended follow-up visits.

Other types of insulin include NPH, Novolin N, Vetsulin, and PZI (ProZinc). Of these, PZI usually works the most consistently and has a longer duration of action. But as with Lantus, it is more expensive.

Oral diabetes drugs for cats

Oral diabetes medication, such as Glipizide, can be used, but most veterinarians prefer that cats be treated with injectable insulins. The oral medications do not work as well in cats, and it’s often easier for people to give a cat injections rather than pills. However, there are some circumstances in which oral medication might be used. Some people are very uncomfortable around needles, and some cats won't allow injections but will eat the oral medication in food.

Diet change and weight loss

The other mainstay of feline diabetes treatment is diet change, an important part of possibly getting a cat to go into remission. Feeding a high-protein, low-carbohydrate diet allows the insulin to work better and helps the cat to lose weight. Canned food is better than dry food because it is lower in carbohydrates, is not as calorie-dense, and contains more fluid.

In conjunction with a change in diet, weight loss is a vital part of diabetes management. Weight loss is often achieved by feeding the cat a high-protein, low-carbohydrate diet, but it is also achieved by only feeding a certain amount of food at designated meal times. Feeding at select times also makes it easier to ensure that the cat will eat, which then allows insulin to be administered.

Exercise programs also help with weight loss and management in cats. Exercise can include taking the cat for walks using a harness and leash, having the cat chase toys, or even encouraging the cat to “hunt” for food if kibble is still being fed.

Treating other medical conditions

To help with diabetes control, any other disease conditions should be diagnosed and treated. Infections can lead to insulin resistance, as can other systemic diseases such as kidney disease, heart disease, or overactive adrenal glands. Some of the most common interfering conditions include urinary tract infections and dental disease.

Natural or holistic therapies for diabetes

There are no proven natural or holistic therapies to treat diabetes. However, some veterinarians might use some holistic or herbal therapies that they have found beneficial. And, technically, switching the cat to a high-protein, low-carbohydrate diet is a “natural” treatment.

Important considerations when giving a cat insulin

No matter which type of insulin is used, it is vital that the cat eats before the insulin is given. It is much more dangerous for a cat’s blood sugar to drop too low than to stay elevated for an extra day.

The concentration of the insulin being used is also important because there are different insulin syringes that are calibrated to work with different concentrations of insulin. The syringes are labeled for the concentration of insulin with which they should be used. If the wrong syringe is used, the cat might either be overdosed or underdosed.

Determining the optimal insulin dosage

Some veterinarians like to hospitalize the cat on the first day of insulin treatment to ensure that the cat does not become hypoglycemic (i.e., the cat's blood sugar has dropped too low). If the cat's blood sugar level does drop too low, the vet might elect to lower the insulin dose. Normally, insulin doses are not increased after this first day, as not enough time has passed for the cat to adjust to the insulin.

It can take weeks to find the correct dose of insulin. To determine whether the dose needs to be changed, a veterinarian might do a glucose curve seven to 14 days after the insulin is started. The cat will stay in the hospital and have their blood sugar checked every two to four hours to determine how low the glucose level goes and how long after the insulin is given it happens. Based on the results, the vet might alter the dose of insulin.

Alternatively, the cat’s person can perform the glucose curves at home with the use of a glucometer, an in-home glucose-measuring device. These are relatively easy to use, and most people can become quite comfortable using them.

Because cats are prone to stress hyperglycemia (their blood sugar goes up when they are nervous), a stress reaction might have an effect on an in-hospital glucose curve. So it’s one reason to have the cat’s person do the glucose curves at home. The vet could also run a fructosamine level to get an idea of what the blood sugar has been over the past seven to 14 days. This is a good idea for cats who are really stressed in the hospital and whose people are unable to perform the curves at home. However, a fructosamine level cannot tell how low the insulin goes nor at what time past the insulin administration is the low point in the blood sugar.

It is also important for people to monitor their cats’ clinical signs at home. An increase in activity and a decrease in weight, water consumption, and urine production are indicators of response to therapy. If the lab tests are off but the cat is acting a lot better, it might be possible to make smaller adjustments to treatments. People also need to look for signs of hypoglycemia (low blood sugar), including weakness, collapse, seizures, wobbliness, disorientation, and excessive drooling. If these signs are noted, the cat should be given a little sugar water or Karo syrup and taken to a veterinary hospital immediately.

Untreated diabetic cats

If diabetes is left untreated, the cat will go into a condition call diabetic ketoacidosis (DKA). In essence, because the cat has not been able to use glucose for energy, the cat starts making ketones to be used for energy. As these ketones build up, the body can no longer function, and the cat will die without treatment. The treatment is usually three to 10 days of intensive hospitalization, usually in a 24-hour veterinary hospital. If the DKA is treated but therapy is not started to control the diabetes afterward, the same thing will happen again.

Costs of caring for a diabetic cat

The costs can vary quite a bit from cat to cat. The variability in cost comes from the type of insulin used, concurrent diseases, whether the cat’s person is able to do follow-up glucose curves at home, the cost of food, and how long a bottle of insulin lasts.

In general, expect to spend the following:

  • Insulin: The cost ranges from $35 to $325 a bottle. Again, the more expensive bottle might actually be less expensive in the long run because less is needed and there is a greater chance of remission. A bottle will last anywhere from one to six months.
  • Glucose curves: Depending on how the veterinarian elects to do them, the cost can range from $40 to $200 every two to four weeks until the cat is well regulated and then every one to six months thereafter. Again, there is a lot of variability between veterinarians’ choices and individual cats’ needs. If the cat’s person elects to do the glucose curves at home, a starter glucometer kit (blood-measuring kit) costs about $40 to $50, and this kit will do up to 10 curves as well as some spot glucose checks.
  • Concurrent diseases: In cats who have concurrent diseases, the vet might need to do follow-up urinalysis, full blood panels, or even specialized endocrine testing.

Prognosis for feline diabetes

The prognosis for a cat with diabetes depends on a number of things. Poor indicators of long-term control over the disease include other endocrine diseases, such as an overactive adrenal gland and an overactive pituitary gland. If a cat develops ketoacidosis and cannot get out of this state, or is in this state during follow-up visits, there is a correlation with poor long-term survival.

For most diabetic cats, the ability of the cat’s person to manage their cat is the biggest factor when it comes to prognosis. For instance, if the person cannot consistently give the insulin, the cat tends to do worse and is hard to regulate. Also, if the cat won't eat a canned high-protein food, it's harder to get good control of the cat's blood sugar.

It's not possible to cure a diabetic cat, but it is possible for the cat to go into remission. Being in remission means that the cat doesn't need insulin for four months. However, even in remission, a diabetic cat typically needs to stay on a high-protein diet. The cat also should have their blood sugar checked frequently and have an exam done by a vet to make sure the cat doesn't require insulin again.

Diabetic cats do require more extensive veterinary care, but those who have their blood sugar adequately managed can live for years.