Feline Diabetes

Annabessacook Veterinary Clinic
417 Route 135
Monmouth, Maine 04259

Diabetes Mellitus in Cats

There are two forms of diabetes in cats: diabetes insipidus and diabetes mellitus. Diabetes insipidus is a very rare disorder that results in failure to regulate body water content. Your cat has the more common type of diabetes, diabetes mellitus. This disease is seen on a fairly regular basis, usually in cats 5 years of age or older. Simply put, diabetes mellitus is a failure of the pancreas to regulate blood sugar. The pancreas is a small but vital organ that is located near the stomach. It has two significant populations of cells. One group of cells produces the enzymes necessary for proper digestion. The other group, called beta cells, produces the hormone called insulin.

Types of Diabetes

In cats, two types of diabetes mellitus have been discovered. Both types are similar in that there is a failure to regulate blood sugar, but the basic mechanisms of disease differ somewhat between the two groups.

1. Type I, or Insulin Dependent Diabetes Mellitus, results from total or near-complete destruction of the beta cells. This is the most common type of feline diabetes. As the name implies, cats with this type of diabetes require insulin injections to stabilize blood sugar.

2. Type II, or Non-Insulin Dependent Diabetes Mellitus (NIDDM), is different because some insulin-producing cells remain. However, the amount produced is insufficient, there is a delayed response in secreting it, and the tissues of the cat’s body are relatively resistant to it. These cats may be treated with an oral drug that stimulates the remaining functional cells to produce or release insulin in an adequate amount to normalize blood sugar. Alternatively, they may be treated with insulin. Cats with NIDDM may ultimately progress to total beta cell destruction and then require insulin injections.

What Insulin does for the Body

The role of insulin is much like that of a gatekeeper. It stands at the surface of body cells and opens the door, allowing glucose to leave the blood stream and pass inside the cells. Glucose is a vital substance that provides much of the energy needed for life, and it must work inside the cells. Without an adequate amount of insulin, glucose is unable to get into the cells. It accumulates in the blood, setting in motion a series of events that can lead to serious long-term problems.

When insulin is deficient, the cells become starved for a source of energy. In response to this, the body starts breaking down stores of fat and protein to use as alternative energy sources. As a consequence, the cat eats more; thus, we have weight loss in a cat with a ravenous appetite. The body tries to eliminate the excess glucose by eliminating it in the urine. However, glucose (blood sugar) attracts water; thus, urine glucose takes with it large quantities of the body's fluids, resulting in the production of a large amount of urine. To avoid dehydration, the cat drinks more and more water. Thus, we have the four classical signs of diabetes:


Weight loss
Ravenous appetite
Increased water consumption
Increased urination

Diagnosing Diabetes

The diagnosis of diabetes mellitus is based on three criteria: the four classical clinical signs, the presence of a persistently high level of glucose in the blood stream, and the presence of glucose in the urine.

The normal level of glucose in the blood is 80-120 mg/dl. It may rise to 250-300 mg/dl following a meal or when the cat is very excited; however, diabetes is the only common disease that will cause the blood glucose level to rise above 400 mg/dl. Some diabetic cats will have a glucose level as high as 800 mg/dl, although most will be in the range of 400-600 mg/dl.

To keep the body from losing its needed glucose, the kidneys do not allow glucose to be filtered out of the blood stream until an excessive level is reached. This means that cats with a normal blood glucose level will not have glucose in the urine. Diabetic cats, however, have excessive amounts of glucose in the blood, so it will be present in the urine.

What It Means for Your Cat to be Diabetic

For the diabetic cat, one reality exists. Blood glucose cannot be normalized without treatment. Although the cat can go a few days without treatment and not get into a crisis, treatment should be looked upon as part of the cat's daily routine. Treatment almost always requires some dietary changes. Whether an individual cat will require oral therapy or insulin injections will vary.

As for the owner, there are two implications: financial commitment and personal commitment.

When your cat is well regulated, the maintenance costs are minimal. The special diet, the oral medication, insulin, and syringes are not expensive. However, the financial commitment can be significant during the initial regulation process and if complications arise.

In some cases, your cat will be hospitalized for a few days to deal with the immediate crisis and to begin the regulation process. The "immediate crisis" is only great if your cat is so sick that it has stopped eating and drinking for several days. Cats in this state, called ketoacidosis, may require a week or more of hospitalization with quite a bit of laboratory testing. Otherwise, the initial hospitalization may be only for a day or two to get some testing done and to begin treatment. At that point, your cat goes home for you to administer medication. At first, return visits are required every 5-7 days to monitor progress. It may take a month or more to achieve good regulation.

The financial commitment may again be significant if complications arise. We will work with you to achieve consistent regulation, but some cats are difficult to keep regulated. It is important that you pay close attention to our instructions related to administration of medication, to diet, and to home monitoring. Consistency is the key to prolonged regulation. The more you keep the medication, diet, and activity the same from one day to the next, the easier it will be to keep your cat regulated.

Another complication that can arise is hypoglycemia or low blood sugar; if severe, it may be fatal. This may occur due to inconsistencies in treatment or because some cats can have a spontaneous remission of their disease. This will be explained in subsequent paragraphs.

Your personal commitment to treating this cat is very important in maintaining regulation and preventing crises. Most diabetic cats require insulin injections twice daily, at about 12-hour intervals. They must be fed the same food in the same amount on the same schedule every day. If you are out of town, your cat must receive proper treatment while you are gone. These factors should be considered carefully before deciding to treat a diabetic cat.


As mentioned, the key to successful treatment is consistency. Your cat needs consistent administration of medication, consistent feeding, and a stable, stress-free lifestyle. To best achieve this, it is preferred that your cat lives indoors. Although that is not essential, indoor living removes many uncontrollable variables that can disrupt regulation.

The first step in treatment is to alter your cat's diet. Diets that are high in protein and low in carbohydrates are preferred because they are generally lower in sugar and slower to be digested. This means that the cat does not have to process a large amount of sugar at one time. If your cat is overweight, a reducing-type diet is fed until the proper weight is achieved, then your cat is switched to a diabetic maintenance food.

Your cat's feeding routine is also important. The average cat prefers to eat about 10-15 times per day, one mouthful at a time. This means that food is left in the bowl at all times for free choice feeding. Unfortunately, this makes monitoring food intake and managing blood sugar much harder. We recommend feeding your pet canned food from the approved foods list below twice daily. We realize that if you have more than one cat, this may be difficult, but please make an effort, as this is part of the consistent treatment that should occur. If this absolutely will not work for you, please let us know so that we can discuss other alternatives.

The second step in treatment is to use a drug to control (lower) control blood glucose levels. The choices are to give insulin injections or to give an oral drug. Oral hypoglycemic agents do not work as well and many cats will eventually require insulin. This being so, we recommend starting your cat on insulin sooner rather than later.

Insulin injections are usually the first choice because this approach is to replace the hormone that is missing or made in inadequate amounts. Although may people are initially uncomfortable with the thought of giving injections, for most cats, insulin injections are easier than giving tablets for reasons described below.

Many people are initially fearful of giving insulin injections. If this is your initial reaction, consider these points.

1) Insulin does not cause pain when it is injected.
2) The injections are made with very tiny needles that your cat hardly feels.
3) The injections are given just under the skin in areas in which it is almost impossible to cause damage to any vital organ. Please do not decide whether to treat your cat with insulin until we have demonstrated the injection technique. You will be pleasantly surprised at how easy it is.

Insulin Therapy and Administration

About Insulin

Insulin comes in an airtight bottle that is labeled with the insulin type and the concentration. Before using, mix the contents. It says on the label to roll it gently, not shake it. The reason for this is that insulin has a fragile crystalline structure and vigorous shaking can actually damage the insulin, making it less effective.

Insulin is a hormone that will also lose its effectiveness if exposed to direct sunlight or high temperatures. It should be kept in the refrigerator, but it should not be frozen. It is not ruined if left out of the refrigerator for a day or two as long as it is not exposed to direct sunlight. However, we do not advise this. Insulin is safe as long as it is used as directed, but it should be kept out of reach of children. We recommend that the same person give the insulin each day to reduce the chance of missed or repeated doses.

Several types of insulin are used in cats. Some are made for use in humans and obtained from regular pharmacies. Protamine zinc insulin (PZI) is made specifically for cats and obtained from veterinarians. PZI has a concentration of 40 units of active insulin crystals per milliliter of fluid. Thus it is called U40 insulin. Insulins made for humans have a concentration of 100 units per milliliter and are called U100 insulins. This is important to know because there are two types of insulin syringes, U40 syringes and U100 syringes. They are made to be used with their respective types of insulin and must not be interchanged or improper dosing will occur. We recommend using one of two types of insulins in cats. The first insulin is called glargine (tradename Lantus). Glargine is a human insulin that is dosed twice daily in cats. Recent studies have shown glargine to have a long duration of action in cats with less peaks and valleys than traditional insulin. Some studies have even reported remission of diabetes in cats treated with this type of insulin. Glargine is a U100 insulin.

The second type of insulin recommended for use in cats is PZI. This is a human insulin that is designed for use in dogs in cats. Similar to glargine some studies have shown PZI to have less peaks and valleys than other insulins. PZI is a U40 insulin.

Drawing up Insulin

A new, sterile syringe should be used at each injection. Have the syringe and needle, insulin bottle, and cat ready. Then, follow these steps:

1) Remove the guard from the needle, and draw back the plunger to the appropriate dose level.
2) Carefully insert the needle into the insulin bottle.
3) Inject air into the bottle; this prevents a vacuum from forming within the bottle.
4) Withdraw the correct amount of insulin into the syringe.

Before injecting your cat with the insulin, verify that there are no air bubbles in the syringe. If you get an air bubble, draw twice as much insulin into the syringe as you need. Then withdraw the needle from the insulin bottle and tap the barrel of the syringe with your finger to make the air bubble rise to the nozzle of the syringe. Gently and slowly expel the air bubble by moving the plunger upward.

When this has been done, check that you have the correct amount of insulin in the syringe. The correct dose of insulin can be assured if you measure from the needle end, or "0" on the syringe barrel, to the end of the plunger nearest the needle.

Injecting Insulin

The steps to follow for injecting insulin are:

1) Hold the syringe in your right hand (switch hands if you are left-handed).
2) Have someone hold your cat while you pick up a fold of skin from somewhere along your cat's back with your free hand (pick up a different spot each day).
3) Quickly push the very sharp, very thin needle through your cat's skin. This should be easy and painless. However, take care to push the needle through only one layer of skin and not into your finger or through two layers of skin. The latter will result in injecting the insulin onto your cat's hair coat or onto the floor. To ensure that you have not gone all the way through the skin, you can gently pull back on the plunger. If you are in the correct spot, negative pressure will be felt when pulling back the plunger. The needle should be directed parallel to the backbone or angled slightly downward.
4) To inject the insulin, place your thumb on the plunger and push it all the way into the syringe barrel.
5) Withdraw the needle from your cat's skin. Immediately place the needle guard over the needle and discard the needle and syringe. Needles/syringes should be properly disposed of in an approved medical waste container. These containers can be purchased at your local pharmacy. Medical waste such as this CANNOT be put into regular trash.
6) Stroke your cat to reward it for sitting quietly.

It is neither necessary nor desirable to swab the skin with alcohol to "sterilize" it. There are four reasons:

1) Due to the nature of the thick hair coat and the type of bacteria that live near the skin of cats, brief swabbing with alcohol or any other antiseptic does not really kill all the bacteria.
2) Because a small amount of alcohol can be carried through the skin by the needle, it may actually carry bacteria with it into the skin
3) The sting caused by the alcohol can make your cat dislike the injections.
4) If you have accidentally injected the insulin on the surface of the skin, you will not know it. If you do not use alcohol and the skin or hair is wet following an injection, the injection was not done properly.

Although the above procedures may at first seem complicated and somewhat overwhelming, they will very quickly become second nature. Your cat will soon learn that once or twice each day it has to sit still for a few minutes. In most cases, a reward of stroking results in a fully cooperative cat that eventually may not even need to be held.


It is necessary that your cat's progress be checked on a regular basis. Monitoring is a joint project on which owners and veterinarians must work together.

Home Monitoring

Home monitoring can take many forms depending on your comfort level. Oftentimes, many owners find it easy to keep a journal of their cat’s activities. You should be aware of your cat's appetite, weight, water consumption, and urine output. You should be feeding a constant amount of food each day, which will allow you to be aware of days that your cat does not eat all of it or is unusually hungry after the feeding. You should weigh your cat at least twice monthly. It is best to use the same scales each time. A baby scale works well for this. If you have several cats that eat together and use the same litter box, monitoring weight is the best because it is specific to this one cat.

If possible, you should develop a way to measure water consumption. The average 10 pound (4.5 kg) cat should drink no more than 7 1/2 oz. (225 ml) of water per 24 hours. Since this is highly variable from one cat to another, keeping a record of your cat's water consumption for a few weeks will allow you to establish what is normal for your cat. Another way to measure water consumption is based on the number of times it drinks each day. When properly regulated, it should drink no more than four times per day. If this is exceeded, you should take steps to make an actual measurement.

Any significant change in your cat's food intake, weight, water intake, or urine output is an indicator that the diabetes is not well controlled. We should see the cat at that time for blood testing.

Another form of home monitoring is to determine the presence of glucose and ketones in the urine. If your cat is properly regulated, there should be no glucose or ketones present in the urine.

There are several ways to detect glucose and ketones in urine. You may purchase urine glucose test strips in any pharmacy. The most common name for these strips is KetoDiastix. They are designed for use in humans with diabetes, but they will also work in the cat. The use of special non-absorbing kitty litter permits you to dip the test strip into urine in the litter box. Aquarium gravel or commercial non-absorbing litter can be used. Urine should be tested at least once a week or whenever you feel that your cat’s diabetes isn’t being properly regulated.

If glucose is not detected, the test should be repeated the next two days. If it is absent each time, we should see your cat for a blood test. If, at any time, ketones are detected in the urine, please call us as this can be a sign that your cat is becoming ill.

Monitoring of Blood Glucose

Determining the level of glucose in the blood is the most accurate means of monitoring. This can be easily accomplished at home if you have the proper equipment. Home monitoring of blood glucoses is often the best way to manage diabetic cats long-term as it eliminates the stress and trouble of bringing your cat to the veterinarian’s office for blood glucose checks. We would be happy to assist you in obtaining a glucometer for home use and instructing you on the correct way to obtain a blood sample. Although this may seem daunting, it is a very simple procedure that is usually well-tolerated by most cats.

During the initial phase of regulating your cat’s diabetes, we will need to perform regular “spot checks” of blood glucose levels to ensure that our insulin dose and schedule is having the desired effect. We will help you determine when these checks should be made. Also, approximately 5-7 days after starting insulin treatment, we will need to perform a blood glucose curve. This is done by giving the insulin at a specified time and taking blood glucose measurements are regular intervals. This can be done in the hospital or at home if you are comfortable with your glucometer. Please see the monitoring summary below for more complete instructions.

Once we have achieved good control of your cat’s diabetes, we will work with you to develop a plan for regular monitoring of blood glucoses. It is vitally important that you DO NOT change insulin doses without first consulting with a doctor. Even small changes in dose can have very serious side effects. Too much insulin can cause severe hypoglycemia and even death.


Hypoglycemia means low blood sugar. If it is below 40 mg/dl, it can be life threatening. Hypoglycemia occurs under three conditions:

1) If the insulin dose is too high. Although most cats will require the same dose of insulin for long periods of time, it is possible for the cat's insulin requirements to change. However, the most common causes for change are a reduction in food intake and an increase in exercise or activity. The reason for feeding before the insulin injection is so you can know when the appetite changes. If your cat does not eat, skip that dose of insulin. If only half of the food is eaten just give a half dose of insulin. Always remember that it is better for the blood sugar to be too high than too low. If you ever have any questions or concerns about dosing of insulin, please call our office prior to administration.

2) If too much insulin is given. This can occur because the insulin was not properly measured in the syringe or because two doses were given. You may forget that you gave it and repeat it, or two people in the family may each give a dose. A chart to record insulin administration will help to prevent the cat being treated twice.

3) If your cat has a spontaneous remission of the diabetes. This is a poorly understood phenomenon, but it definitely occurs in at least 20% of diabetic cats. They can be diabetic and on treatment for many months, then suddenly no longer be diabetic. Since this is not predictable and happens quite suddenly, good monitoring of your cat’s habits and regular vet visits are key.

The most likely time that a cat will become hypoglycemic is the time of peak insulin effect (5-8 hours after an insulin injection). When the blood glucose is only mildly low, the cat will be very tired and unresponsive. You may call it and get no response. Within a few hours, the blood glucose will rise, and your cat will return to normal. Since many cats sleep a lot during the day, this important sign is easily missed. Watch for it; it is the first sign of impending problems. If you see it, please bring in your cat for blood testing.

If your cat is slow to recover from this period of lethargy, you should give it corn syrup (1 tablespoon by mouth) or feed one packet of a semi-moist cat food. If there is no response in 15 minutes, repeat the corn syrup or the semi-moist food. If there is still no response, contact us immediately for further instructions.

If severe hypoglycemia occurs, a cat will have seizures or lose consciousness. This is an emergency that can only be reversed with intravenous administration of glucose. If it occurs during office hours, come in immediately. If it occurs at night or on the weekend, please call the Animal Emergency Clinic in Lewiston at 777-1110.

Monitoring Summary

Ongoing Home Monitoring for All Cats
 Log food, water and appetite daily
 Log insulin dose daily
 Note any signs of hypoglycemia (Alert veterinarian if persistent)
 Periodically test urine

At 1 week after initiating insulin treatment
 Blood glucose curve
If clinical signs have improved and no ketones in urine:
 Begin home blood glucose monitoring, if applicable
 Spot blood glucose check
If clinical signs have persisted or worsened:
 Discuss insulin administration, handling
 Insulin dose may be increased at veterinarian’s discretion
 May need further testing to rule out complicating factors such as infections

During the first month after initiating insulin treatment
 In-clinic (if home monitoring is not possible)
    o Weekly
 Spot blood glucose check 6-8 hours after administration
o Insulin dose may be changed
 Urinalysis to check for ketones, glucose and/or infection
 May perform blood glucose curve
    o Every 2 weeks
 Perform blood glucose curve
 Home
    o Weekly
        Spot blood glucose checks (6-8 hours after administration)
        Urine dipsticks to look for glucose and ketones
o Every 2 weeks
       Perform blood glucose curve

At 1 month after initiating insulin treatment
      In-clinic examination recommended for all cats
o Fructosamine blood test may be needed based on monitoring results

Long-term monitoring of insulin treatment
 At Home:
 Daily: Clinical signs, food/water intake, insulin dose
 Weekly: Body Weight
 Biweekly: Urine glucose and ketones
 Monthly: Spot blood glucose checks
 In-clinic
o Any of the above that cannot be performed at home
o Every 3 months: Examination, including weight
o Every 6-12 months: Full laboratory analysis

Blood Glucose Curve Instructions
 Please do not perform blood glucose curves without direction of your veterinarian.
 After you obtain the results of the curve, please contact your veterinarian for interpretation and further instructions regarding changes in insulin therapy. There will be a consultation fee for this. DO NOT MAKE ANY CHANGES TO THE INSULIN DOSE WITHOUT CONSULTING YOUR VETERINARIAN.
 Procedure:
1. Obtain a blood glucose prior to feeding your cat or administering insulin
2. Feed your cat’s normal meal and administer insulin after he/she has eaten
3. Measure a blood glucose every 2-3 hours (if on PZI) or every 4 fours (if on Glargine) for up to 10-12 hours. Ideally values should be obtained up until next insulin dose is due.
4. Contact our office with results.

Approved Foods List

Over the Counter Canned Food Diets Suitable for Diabetic Cats

Friskies Senior Turkey & Giblets
Fancy Feast Turkey Giblets Feast
Friskies Canned Cat Beef and Liver Dinner
Friskies Canned Cat Turkey and Giblets Dinner
Friskies Kitten Formula Turkey
Fancy Feast Flaked Fish And Shrimp
Friskies Special Diet Turkey & Giblets
Fancy Feast Chunky Chicken
Iam’s Kitten
Purina Pro Plan Turkey Rice Entrée Ground
Purina Pro Plan Total Care Kitten Chicken & Rice
Purina Pro Plan Adult Ocean Fish and Crab
Purina Pro Plan Sardines & Tuna in Aspic