Sugar diabetes, more correctly know as diabetes mellitus, is a complex disease that is difficult to control, particularly in cats. Proper treatment requires a significant commitment on your part, usually for the life of your pet. This page describing diabetes disease is very thorough and will require some time in reading if you want to understand it fully.

A glossary of medical terms will be used in this page:

euglycemia– normal blood glucose level

polyphagia– excess appetite

hypoglycemia– low blood glucose level

polyuria– excess urinating

hyperglycemia– high blood glucose level

polydypsia– excess drinking

glycosuria– high glucose in the urine

PU/PD– polyuria and polydypsia

ketonuria– ketones in the urine

DKa– diabetic ketoacidosis


Normal Physiology

In response to a decreasing blood glucose level the appetite center in the brain is stimulated and hunger ensues. A meal is then eaten, which consists of fats, carbohydrates, and proteins in different percentages. When these fats, carbohydrates, and proteins are broken down by the digestive system and absorbed into the bloodstream they are used by the body for differing functions. The main function of the carbohydrates is eventual conversion to an energy source in the form of glucose, the primary energy source for all cells in the body. Some of this glucose is stored in the liver in the form of glycogen, which is released and converted back to glucose when cells need energy in-between meals.

Once in the bloodstream the glucose that circulates throughout the body is available for use by all cells as their primary energy source. These individual cells cannot absorb this glucose that passes by in the bloodstream unless the hormone insulin is circulating in the bloodstream at the same time. Insulin causes a chemical reaction in the cell wall that allows the glucose to enter the cell. The only cells in the body that do not need insulin to absorb glucose are specific brain cells.

This is a picture of the pancreas from a cat. It is adjacentt to the beginning part of the small intestine called the duodenum. The pancreas is the pinkish tissue directly underneath the cylindrical duodenum. For such a small organ it has an important job.


The relative lack of insulin causes the blood glucose to go abnormally high. Normal blood glucose in a cat varies from 80 to 150, but can temporarily go much higher (300-400 or more) in stressful situations. When the blood glucose is consistently high, as seen in diabetes mellitus, several negative effects occur.

Inadequate insulin levels force the cell to perform its functions with alternative sources of energy besides glucose. This causes problems for the organ that is made up of these cells and eventually will lead to significant disease and the complications that occur in untreated diabetes mellitus.

The cells of the body (except most brain cells) are deprived of their primary source of energy. This means they do not function at optimum efficiency. Since they are starved of glucose they need to rely on other sources of energy, namely fat and amino acids. These are not as good an energy source as glucose in the long run.

Why the pancreas stops secreting adequate levels of insulin is a mystery. There is a strong correlation for diabetes mellitus to occur in cats that previously had an episode of pancreatitis. This makes sense because the pancreas is the source of insulin. Yet, many cats that have diabetes mellitus had no apparent pancreatitis in the past. In some cats the immune system attacks the beta cells in the islets and deposits a compound called amyloid which makes the beta cells unable to secrete insulin. This amyloid, which contains a protein called amylin, is thought to play a significant role in non-insulin-dependent diabetes (your will learn about this soon).


Most people are familiar with the classification scheme used in human medicine. Even though the disease is similar in people and cats, the human classification scheme does not always correlate with diabetes mellitus in cats. Differentiating between Type I and Type II in cats can be difficult.

Type I

Has similarities to insulin dependent or juvenile onset diabetes mellitus. Most commonly occurs in middle aged cats. Insulin is needed to treat the problem. This is also known as insulin dependent diabetes mellitus (IDDM).

Type II

Similar to adult onset or non-insulin-dependent in humans. Obesity is a significant risk factor. Insulin is not needed in all cases. Type II cats can become Type I cats when exposed to significant stress. Fortunately, when the stress is resolved they can revert back to Type I. This is also known as non-insulin dependent diabetes mellitus (NIDDM).

Diabetes can occur secondary to other problems. Some of these problems include hormone imbalances and reactions to medications. A medication called Ovaban, a hormone used to treat numerous cat ailments, can cause diabetes.


The classic signs of a cat with diabetes mellitus are PU/PD. These signs are subtle at the beginning stages of the disease and are easily missed. This is especially true in outdoor cats who do most of their urinating outside.

Other symptoms include weakness, an increase in appetite, occasionally a decrease in appetite, weight loss, lethargy and rarely, vision problems due to cataracts (this problem is more common in dogs). Cats with a severe liver problem associated with this disease might have icterus (jaundice).

These are also the symptoms of other diseases commonly seen in cats, and can only be differentiated by diagnostic tests. These other diseases include, but are not limited to, hyperthyroidismkidneydisease, cancerliver diseaseCushing’s disease and adverse reaction to medications.

The yellow discoloration to these gums is icterus. It is commonly, but not always, caused by liver disease.


By the time a diagnosis of diabetes mellitus is made the disease process has been present for a significant period of time. When the disease process first started the cat did not show any symptoms because of compensatory mechanisms in the body. As diabetes progresses these compensatory mechanisms lose their ability to maintain euglycemia. Eventually, symptoms of PU/PD and weight loss occur and the cat is brought in to be examined. This emphasizes the point that middle aged and older cats should have a routine blood panel and urinalysis every year once they reach 8.

This is a complex disease, and no specific set of symptoms tells us your pet has diabetes mellitus. It is important to follow the tenets of the diagnostic process closely when making a diagnosis of diabetes mellitus, especially since kidney disease and hyperthyroidism have similar symptoms. We will use the diagnostic process as an example of how we make this diagnosis:


Typically this disease is seen in obese cats that are middle aged or older, and more commonly in males (the opposite of dogs). There is no specific breed predilection in cats.


The classic signs of PU/PD, polyphagia, and weight loss occur in many cases, but not all. These signs depend on how well entrenched the disease process is before the cat is brought in for an examination. Sometimes the only thing an owner notices is accidents around the house in a previously housebroken cat.

Since this disease occurs in middle aged and older pets there can be other diseases occurring simultaneously. Some cats have a history of vomiting in the recent past, an indication that they might have had an episode of pancreatitis. Some cats are borderline diabetics that have had a recent illness, stress, or adverse reaction to medication. There might also be blood in the urine or straining to urinate, an indication of a urinary tract infection.

Cats presented in DKa might have a history of abdominal pain and distention, vomiting, inappetance, and lethargy.

Physical Examination

The findings of the physical exam depend on how severe the diabetes is, how long it has been present, what caused it, and if there are any other disease processes occurring simultaneously.

Many cats will have lost weight, yet they still could be obese. There might be dehydration, weakness, lethargy, an enlarged liver on abdominal palpation, and an acetone (juicy fruit) smell to the breath. Hypothermia and shock could be present in advanced cases and those with DKa.

Diagnostic Tests

The primary method of diagnosis is with a blood panel and a urinalysis. The blood panel will reveal hyperglycemia (at least > 200 mg/dl) while the urine sample will reveal glycosuria. Not every case of hyperglycemia means a cat has diabetes mellitus. Cats that recently ate, or those that eat canned foods that are rich in sugar, might have blood glucose levels higher than the normal range. Cats that are on cortisone, are in heat, on phenobarbital medication or hormone medications might also have hyperglycemia.

Cats are unique in that their stress response can cause a tremendous rise (up to 4x normal) in the blood glucose. This is a common occurrence when we take a blood sample in a cat and needs to taken into consideration when we analyze a blood report. This stress induced response is a normal reaction to the release of epinephrine (adrenaline). It is a transitory response and will not persist like the hyperglycemia of diabetes mellitus. These cats sometimes need to adjust to a hospital environment before we are able to determine their true blood glucose level.

Here is a blood glucose report from our lab for a cat that does not have diabetes mellitus. The blood glucose is 317.

This cat has diabetes mellitus, its blood glucose is 390

How do we differentiate them when both are well above the normal range?

Diabetes mellitus is diagnosed when there is a persistent fasting hyperglycemia along with glycosuria, that is consistent with a history of PU/PD and polyphagia.

Other blood tests are sometimes used in this disease. The two more common ones are serum fructosamine and glycosylated hemoglobin. They are used to to distinguish stress induced hyperglycemia from diabetes mellitus, and to also monitor insulin therapy. They give us an indication of what the blood glucose level has been for the preceeding weeks.

In addition to glucose in the urine and ketones, the urinalysis might indicate that a urinary tract infection is present. This is detected by a change in the pH of the urine, excess white or red blood cells, and bacteria.

This is a urinalysis from a cat that has diabetes mellitus. Its glucose is 4+, fortunately,it is negative for ketones, there are no white or red blood cells present, and there are no bacteria visible either. This cat does not have ketonuria or an infection.


Some cases of diabetes mellitus are not straightforward. An obese cat can have NIDDM in its normal, unstressed home environment. These cats are secreting insulin but in low levels. As long as they are in a stress free environment they are able to maintain euglycemia. If they encounter a stressful situation, get sick, or are put on certain medications, their blood glucose will increase. If it goes beyond the renal threshold for glucose, PU/PD will ensue.

These cats are then brought to a veterinarian because of the PU/PD and diagnosed as having diabetes mellitus. They are put on insulin therapy and the problem improves. The problem occurs when these cats are returned to their normal environment and the problem that started the increased blood glucose in the first place (stress, illness, drugs) is now gone. In some of these cases these cats will now become hypoglycemic because they are being given insulin injections when they do not need them. Identifying these cats that have converted from insulin-requiring to non-insuin requiring NIDDM is difficult. This is one of the numerous reasons why diabetic cats should be brought to our hospital every 1- 3 months for a urinalysis and blood glucose curve.


Increasing the complex carbohydrates and fiber in the diet will minimize the rise in blood glucose level as the body digests this food. The food we recommend for this is called Hills W/D. This allows for less fluctuation in blood glucose and easier treatment with insulin. In addition, since many of these cats are obese, the higher fiber will help minimize this problem. Dietary therapy might be all that is needed for the obese cat with NIDDM. A cat that is underweight from diabetes mellitus should not be put on a high fiber diet. Since this disease is prevalent in older cats this change in diet might be met with resistance. In these cases mix the higher fiber food with its regular diet to get some advantage of the higher diet. Do not feed foods that contain excess sugar like semi-moist canned foods.

Oral Hypoglycemics

The goal of oral hypoglycemic medication is to minimize glucose absorption by the intestines and to also minimize the conversion of glycogen to glucose by the liver. They also help increase insulin secretion from the pancreas.

They are used in cats that are not underweight, have negligible ketones in the urine, no indication of pancreatitis or no history of being on medication that could cause hyperglycemia. In conjunction with diet, oral hypoglycemics can sometimes help us differentiate NIDDM form IDDM. Cats with NIDDM will have significantly lower blood glucose levels when checked several days after initiating this protocol.

Some cats will vomit and might even develop hepatitis from oral hypoglycemics. Giving the medication with food helps minimize vomiting.

New oral hypoglycemics are being used in cats with some success, sometimes in conjunction with insulin injections.


For many years the insulin used to treat cats was derived from a beef-pork combination (90% beef and 10% pork) that was used in human diabetes mellitus. The pharmaceutical companies are now relying more on human recombinant (genetically engineered) insulin. This is the insulin source we currently use to treat cats.

The goal of insulin therapy in the cat is to mimic naturally secreted insulin from the pancreas as closely as possible. This can be quite difficult in any species, let alone the cat. The dose of insulin and the type of insulin that is effective will vary from cat to cat. Once a proper dose is initially determined at some point in time in the future this dose will probably change.

Initially, insulin is dosed conservatively in order to see an individual cat’s response and to minimize any chance of hypoglycemia. There are many different types of insulin used.

Regulation in the Hospital

Most diabetic cats need to be regulated (the correct dose of insulin determined) in the hospital. Starting this can take 5 days and sometimes longer. Most cats have well entrenched pathology that is not conducive to rapid change. The dose has to be given in small amounts initially to prevent hypoglycemia. It takes several days for a cat to respond to a change in dose. This initial regulation only gives us a starting point for your cat’s insulin dose since there will be numerous mitigating factors that will affect insulin levels when your cat returns home.

During its hospital stay your cat’s blood glucose level will be checked frequently. This is called a blood glucose curve, and it is a critical part of determining the proper insulin dose for your cat. It is such an important part of monitoring that we use a special blood glucose instrument called an accucheck.

Since it takes several days for a cat to show decrease in blood glucose due to insulin we might not start this curve immediately. The blood glucose curve will give us an idea of how it is reacting to the type and amount of insulin we are using. Every cat is different, so this trending is needed to understand specifically how your cat will react.

Our goal is to get the blood sugar level down to somewhere between 100-250 mg/dl. Some cats are regulated fine even if the blood glucose peaks at greater than 250 mg/dl. It is much better to have a cat that has a slightly high blood glucose level than to try and refine the dose so closely that hypoglycemia is risked.

The first step in the process of running a blood glucose test in our hospital involves taking blood from your pet and putting it on a special strip

The blood has to spend 60 seconds on the tip of the strip before it can be inserted in the blood glucose machine. Here we are at the halfway point (30 seconds have elapsed) in the process.

After 60 seconds we wipe away the excess blood on the strip

Now the strip is inserted in the machine for 2 minutes

This cat’s blood glucose reading is 63 mg/dl. It is hypoglycemic at this point.

In addition to starting insulin therapy we will feed your cat a higher protein, lower carbohydrate food. as was previously described, this will help minimize the fluctuations in blood sugar level. also, pets that exercise need less insulin. In cats this is not as much of a factor as in dogs.

The typical cat needs anywhere from 2-10 units given from once to twice daily. Of course this dose depends on the weight of your cat, the type of insulin used, its diet, its exercise level, and its individual response.

After we have an idea of how your cat is responding to insulin in the hospital we will send him/her home for you to refine the dosage. It may take up to a month to find the optimum dose for your cat. The ultimate goal of long term insulin administration is to achieve a blood glucose level as close to euglycemia as possible. Doing so will minimize the symptoms of diabetes mellitus and minimize the chance of long term complications due to the disease.

We recommend you return for a blood glucose check in 7 days to assess your home therapy. Feed your pet and give it its insulin just prior to dropping your pet off to us in the morning. We will perform a blood glucose curve during the day.

Insulin Injections

It is imperative that you administer the precise amount of insulin required since small changes can have dramatic effects in the cat. Be consistent and give the insulin the same time and at the same location every day. If your cat is on twice daily insulin injections give each morning and evening dose at the same time every day. always feed your cat in the morning prior to giving the insulin. If it does not eat its food skip the morning dose of insulin. If it eats only half of its food, give it only half of its insulin dose. Giving a normal dose of insulin to a cat that is not eating greatly increases the risk of hypoglycemia. You must always err on the side of hyperglycemia instead of hypoglycemia.

The actual administration of insulin is very straightforward. As a matter of fact, it is easier to give insulin injections at home than it is to give SQ (subcutaneous) fluids to cats that have chronic renal failure, a common finding in our hospital. This is because an insulin injection takes 1 second to give, whereas fluids take 5 minutes. The technique used to give insulin injections or SQ fluids is the same- click here to view an actual demonstration of the administration of SQ fluids. When you are finished learning the proper technique return here to finish.

You will never be forced into doing something that makes you feel uncomfortable. While your cat is in the hospital with us you can observe how we give the insulin injections. One of our nurses will demonstrate its proper administration when we release your pet from the hospital. You can return to our hospital for assistance in giving the insulin at any time.

In order to simplify the process we will give you an insulin syringe that has been designed to be used with the specific type of insulin your pet requires. You will be giving insulin in a measurement called “units”, and not in ml (milliliters) or cc (cubic centimeters) as is commonly used in most syringes. A typical insulin syringe is called U-100. If you look back at the 3 insulin bottles above you will notice that they have 100 units per ml, which is why we use the U-100 syringe with them. Another type of insulin syringe is called U-40. A U-40 syringe is used if the insulin bottle contains 40 units per ml.

This is what a U-100 syringe looks like. The needle is very small and sharp so your cat will not feel it during its injection.

Insulin should be kept refrigerated at all times to preserve its freshness, although this is not mandatory. Prior to use it should be gently warmed in your hands. Storing the insulin bottle on its side in the refrigerator will help in mixing.

Gently roll it (never shake it vigorously because excess bubbles will form) between your hands for 1-2 minutes to bring it to the proper temperature for administration

Make sure you are in a relatively calm location when you give the injection. Hold the insulin bottle upside down and draw out slightly more than the number of units your cat requires. Tap the syringe a few times to remove any air bubbles-this aids in accuracy (a few tiny bubbles are OK). Push the plunger in the syringe slightly forward until you have the exact number of units you need to administer is in the syringe. Put the cap back on the syringe and put the insulin bottle back in the refrigerator. Do not reuse the syringe.

In no time you will be an expert at this

Give the injection in the scruff of the neck just as you would when giving SQ fluids described above. Your pet should not feel anything because the needle is so tiny and sharp. The whole process, from warming the insulin to giving the injections, should only take a couple of minutes. As you get confidence it is recommended to rotate your injection sites. We can shave a section of hair to make this whole process easier.

Improper administration of insulin is one of the most common causes for improper regulation. Please do not hesitate to contact us at any time for assistance in this vital procedure.

Home Monitoring

Determining the daily dose of insulin required at home is not an easy task. The best way to monitor your pets blood glucose at home is to perform the blood glucose yourself. Ears and pads are areas in which a small prick will give sufficient amount of blood to run an in home blood glucose. In some cats this method of obtaining a blood glucose level is preferable to running a glucose curve in the hospital. This is because the stress of the car ride and the obtaining of blood several times while in the hospital can mislead us as to your cats actual blood glucose level.

Most people prefer to monitor the glucose in their cat’s urine because it is simpler. Monitoring of the glucose in your cats urine will give you at best a rough idea of its blood glucose level. There are significant limitations to home monitoring using urine glucose as a criteria, and we do not recommend it.

Urine glucose measurements do not necessarily correlate with blood glucose measurements, the more important of the two. Also, if the blood glucose level is below the renal threshold a negative glucose in the urine can not differentiate between euglycemia and hypoglycemia. If you note a significant amount of glycosuria consistently for several days your cat needs a blood glucose curve.

To help in the urine monitoring process your cat’s normal litter can be replaced with special litter that will not absorb urine. You can also use regular paper, newspaper, or even plastic wrap in the bottom of the cage. There is even a special litter that reacts with the glucose in the urine.

One of the more common urine dipstick kits is the Keto-Diastix. In addition to monitoring glucose it also monitors for ketones.

This is the chart on the Keto-Diastix bottle. The box to the far left is negative, which is the goal. The next box to the right is 100 mg/dl. Its OK to have this urine glucose value on occasion.

On the same bottle there is a chart to monitor for ketones in the urine. Your goal is to have negative with an occasional trace.

What is just as important as urine glucose is your subjective interpretation of how your cat is doing. If the original symptoms are greatly reduced then you are probably giving an accurate dose.

One of the ways the urine dipstick can be particularly helpful is in monitoring ketones. Occasional trace ketones is no cause for alarm. Consistent ketonuria in a cat that is not feeling well requires immediate veterinary care.

Another good method to monitor your pet at home is the amount of water it is drinking. A typical cat will drink water from its bowl 3 times per day.

Do not make any changes in insulin dose unless you talk with one of our doctors. Do not make daily changes in insulin doses either, wait 3 days to determine if the new dose is having any effect.

Warning signs that necessitate an exam and blood glucose curve in the hospital:

  • Lethargy or significant increase or decrease in appetite
  • Significant increase in drinking or urinating
  • (100 mg/dl) or more glycosuria for > 2 days
  • Significant ketones in urine for > 2 days

Long Term Care

It must be understood that insulin administration does not cure diabetes mellitus, it only controls it. as you learned above in the physiology section, the body has very sophisticated and refined mechanisms to keep the blood glucose at optimum levels. This can not be replicated easily by giving insulin.

To minimize problems we should monitor your cat’s blood glucose level in the hospital and perform a urinalysis every 3 months. Since cats can exhibit an exaggerated stress response causing a profound hyperglycemia a glucose curve is necessary to ensure accuracy. Every 6 months we should also perform a complete blood panel to look for changes in other organs caused by the diabetes. A further reason to run a complete blood panel every 6 months is to monitor routine age related changes likehyperthyroidism and kidney disease. Diabetes can also predispose your pet to high blood pressure(hypertension).

This long term monitoring is important for another reason. In almost every diabetic cat insulin requirements change, necessitating the need for close monitoring and communication with us. If your cat goes into heat (another reason to spay females and even neuter males) its insulin requirements might change. In some diabetic cats the problem goes away and they no longer have a need for insulin. Giving insulin to these cats can cause hypoglycemia, which if it is severe enough, can lead to seizures.

Complications of Diabetes


One of the more alarming side effects to insulin administration is hypoglycemia. You should be ever vigilant about its appearance and always be ready to treat it at home.

Symptoms include shaking, a starry eyed appearance, lethargy, shaking, greatly enlarged pupils, muscle tremors and even seizures. If the problem is serious and persists long enough coma and even death can occur from depression of the respiratory system. Some pets don’t show any obvious symptoms except subtle behavior changes like sleeping more than usual. Since cats sleep most of the time anyway this can easily be missed.

In most cases the cause is an overdose of insulin. A common scenario involves a cat that eats significantly less than its normal amount for the day. Hypoglycemia can result if the dose of insulin is not adjusted to take this into account. If your cat is not eating well and you are unsure, either give less insulin that day or do not give any at all. A blood glucose test in the hospital will let us know for sure.

Close observation of your cats appetite will go a long way towards preventing this problem. Monitoring its urine for glucose will help since a negative glucose in the urine should be noted. If the urine test for glucose is negative you need to pay particular attention to your insulin administration.

Liver Disease

Cats with diabetes are forced into using an energy source that will eventually cause a fatty infiltration of liver cells. As a result the liver will not function at optimum capacity, a potentially serious problem since the liver is such a vital organ. The liver enzyme test on the blood panel will alert us to this complication. When the diabetes is treated this problem might resolve.

Radiography might reveal an enlarged liver (hepatomegaly) due to the fatty infiltration.This liver is larger than normal-it is extending towards the right far beyond the margin of the ribs. The 4 white arrows on the bottom outline the lower edge of the wedge shaped and enlarged liver.

Keeping the blood glucose level as close to euglycemia as possible will help minimize this complication. Again, the need for periodic blood glucose monitoring along with a routine blood panel every 6 months become obvious.


Diabetic cats are prone to infections, especially of the urinary tract. These infections makes them more prone to DKa and insulin antagonism. Good dental hygiene is critical also since many cats with diabetes have dental disease. Chronic dental disease can make regulation almost impossible.


It is obvious that this is a complex disease that requires diligence on your part for proper control. Since every cat is different, your doctor will make a custom plan that will work for you and your pet, and will not necessarily follow any pre-established protocol. Be prepared for constantly changing insulin requirements and potential complications. The more consistent you are with feeding the same food, in the same amount, at the same time(s) every day, will add to a successful outcome.

The majority of diabetic pets on insulin therapy have a significantly increased quality of life. This usually makes the time economic commitment necessary for proper regulation well worth the effort.