In diabetes mellitus (DM), the pancreas does not produce enough insulin for the body to use sugars, fats, and proteins efficiently.  Uncommon Type I DM is simply too little insulin production within the pancreas. However, Type II DM, affects 85 to 95% of diabetic cats when their cells become resistant to the normal amounts of insulin produced by the pancreas. We diagnose DM when we find high blood sugar (glucose) and accompanying sugar in the urine.


The dramatic rise of DM in cats parallels the same phenomenon in people and mirrors the increasing obesity among both species. Factors linked to DM are:

  • Obesity (easily the most important link)
  • Chronic pancreatitis
  • High carbohydrate diets
  • Other hormonal diseases (hyperthyroidism, Cushing’s disease, acromegaly)
  • Extensive use of steroids


In healthy cats, when blood sugar (glucose) is high, the pancreas releases insulin. That insulin pushes excess glucose into cells where it can be used for immediate energy or stored for later use. With insufficient insulin, diabetic kitties accumulate too much glucose in the blood. While their body cells are starving for this sugar, their kidneys remove excess blood glucose and lose it completely into the urine. This is why diabetic cats eat more than usual but eventually lose weight.

The first symptoms of DM are usually increased thirst and urination. Because sugar draws water to go with it, kidneys have to work harder and harder to keep hydration normal. Sugar in the urine predisposes to bladder infections. We hope to catch DM at this point, before more severe metabolic changes take place. In cats, early diagnosis increases the likelihood of actually reversing diabetes and eventually getting eliminating the need for insulin injections. Look for:

  • Increased thirst and urination
  • Increased appetite, especially when coupled with weight loss
  • Poor skin condition and hair coat, less self-grooming
  • Weakness in the hind legs (diabetic neuropathy)
  • Cataracts (rarely)

As starving body cells continue to demand more glucose, body fat breaks down rapidly, causing liver complications and accumulations of ketones (byproducts of fat breakdown) in the blood, spilling into the urine. The compromised cat feels very ill and loses appetite. Systemic collapse is near with deadly electrolyte imbalances and metabolic failure. This condition is known as diabetic ketoacidosis and is a severe emergency. Watch for these later stage symptoms of uncontrolled diabetes:

  • Lethargy, weakness
  • Decreased appetite
  • Vomiting and diarrhea
  • Dehydration
  • Difficulty in breathing, collapse


In most cases, giving additional insulin by injection lowers blood sugar and allows it into the cells needing it for energy. Cats metabolize most insulins fairly rapidly and so they generally require insulin every 12 hours. Insulin is fragile. Too hot or too cold or excessive shaking may change its potency. Remember the following:

  • Check the expiration date on the bottle
  • Keep refrigerated (not frozen)
  • Do not shake bottle
  • Never insert a used needle into the bottle
  • Insulin syringes are not all calibrated the same. Use the right syringe for your insulin brand. Syringes with ½ inch 29 gauge needles work well. 
  • U40 syringes (available in 20 or 40 unit volumes) are used for Vetsulin and PZI and have 40 U per cc of insulin.
  • U100 syringes (available in 100, 50, or 30 unit volumes) are used for Glargine (Lantus) and have 100 U per cc of insulin. For the small doses required in cats, purchase the 30 unit syringes (.3cc) for most accurate dosing.      
  • Accurate dosing and timing of insulin are very important in treating your diabetic cat.  Shaving an area on your cats back will make beginning insulin users more sure of injecting just under the skin. Follow these steps to success:
  1. Choose a time when you can regularly be home to give insulin 12 hours apart.
  2. Feed your cat half of its daily food allowance before giving insulin. Make sure that your pet has eaten well. (If food is refused, give only half of the normal insulin dose. If this happens repeatedly, check with your veterinarian.)
  3. Roll insulin bottle between your palms to mix gently.
  4. Remove needle cover and protective cap from plunger on syringe.
  5. Draw back plunger to pull air into the syringe, about equal to the amount of insulin to be used.
  6. Holding bottle upside down, inject air into bottle. 
  7. Draw plunger back slowly, pulling in a little more insulin than you will actually need.
  8. Keeping bottle and syringe vertical, tap syringe barrel with finger nail to force air bubbles to rise to the top.
  9. Still vertical, push excess insulin back into bottle, carefully stopping when the front of the plunger is at the desired dose marking.
  10. Pull up loose skin anywhere on the back or sides of your patient, creating a tent between your fingers.
  11. Push needle completely through one layer of skin, into the pocket that is formed by the skin. Push needle all the way in being careful not to go completely through to other side. (Do not keep any finger on the plunger lest you squirt out insulin before you have positioned the needle under the skin.)
  12. Assure yourself that the tip of the needle is completely under the skin and then inject the insulin.
  13. Pinch the skin as you remove the needle. This helps to close the tiny hole you have created.
  14. Twelve hours later, repeat the process.
  15. Occasionally, your kitty may move just as you are injecting insulin and you may have doubts that all the insulin has gone under the skin as it should. Do NOT give additional insulin at that point. Simply wait the 12 hours until the next injection is due and proceed as normal.
  16. Two short videos demonstrating filling the syringe and injecting insulin are available at .     



We feed DM cats a high protein, low carbohydrate, high fiber diet. High protein sates their appetite, helps promote weight loss, and mimics natural rodent and bird diets. Low carbohydrate and high fiber prolong digestion time to prevent the sugar peaks and keep blood glucose more level. Important note: DM cats with poor kidney function should NOT be on high protein food.

Remember that treats need to be low carb, low sugar, or maybe just discontinued. 

We usually start cats on Science Diet MD. In cats that are still overweight, we prefer the canned variety. In thin cats, the dry MD gives the diabetic cat more caloric intake. Science Diet WD is a second option if your cat would like another choice.   

There are many other foods on the market. Here are the figures from MD for comparison if you are searching for an alternative.

Science Diet MD canned

  • protein: 13.1% (as fed) or 52.8% (dry matter)
  • fat: 4.8% (as fed) or 19.4% (dry matter)
  • carbohydrate (NFE): 3.9% (as fed) or 15.7% (dry matter)
  • crude fiber: 1.5% (as fed) or    6%    (dry matter)

Science Diet MD dry

  • protein:  48.9% (as fed) or 52% (dry matter)
  • fat: 20.7% (as fed) or 22% (dry matter)
  • carbohydrate (NFE): 14.6% (as fed) or 15.5% (dry matter)
  • crude fiber: 5.2% (as fed) or 5.5% (dry matter)










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1 2/3



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Diabetic cats should eat most of the first half of their daily food allowance just before the first insulin injection in the morning and most of the other half about 12 hours later, just before the night-time injection. “Grazer” cats, especially thin ones, should be left with some dry food for during the day to help them maintain an adequate weight. Cats on weight loss plans can have only a few tiny snacks during the day.

Weigh your kitty regularly. Obese cats should not lose more than 2% of their body weight per week as we try to slim them down. For a 15 pound cat, that is a little less than 1/3 pound per week. More rapid weight loss may lead to liver disease. 


Initially, your veterinarian will start insulin at a low dose. Continue at that dose for at least a week before beginning to make any alterations. You will need to monitor blood glucose to eventually find the proper dosage and to monitor changes in your cat’s insulin needs. With insulin and proper feeding, we try to keep blood glucose between 75 and 250. Stay in communication with your veterinarian to help you with your adjustments. Whenever you increase the insulin dosage, try to do it on a day when you will be home to monitor your cat’s response. 

(Most cats only require around 3 to 5 units of insulin every 12 hours. Rarely a cat may become “insulin resistant”, defined as requiring more than one unit per pound for regulation OR all glucose levels consistently over 300 all during the day in spite of receiving 6 to 8 units of insulin per dose.)

Observe clinical symptoms. Note excessive urination, thirst, urinating outside the litter box, behavior changes, and physical changes (especially continued weight loss). A well-controlled diabetic returns to “normal” cat behavior.

Urine testing is inexpensive. Urine glucose/ketone strips are available at your pharmacy. While urine does not give you an up to the minute glucose reading, it does tell you if sugar was too high during part of the time during which the urine was formed. It is often easiest to get the first urine of the morning when kitty begins to stir. Some pets will allow you to stick a test strip into the urine stream as they go. With more shy cats, you may have to put some plastic wrap in the litter box so that some of the urine pools on it. Some kitty owners put only a handful of litter into the litter box when they are seeking a sample. Not all the urine will be soaked up and the pooled excess can be tested. Test only fresh urine. Urine testing will NOT alert you to dangerously low glucose levels

  • After a week of continual glucose positive results, raise the insulin dose by ½ unit and continue that for 5 to 7 days. Report each dose change to your veterinarian so periodic blood testing can confirm what you are finding!
  • If urine test strips continue to be positive for the next 5 to 7 days, raise the insulin again by ½ unit and continue testing. 
  • Continue this process until you begin to see slight positive or negative test strips. Then, make an appointment to have a blood glucose curve, a series of timed glucose tests, so that your veterinarian can make sure that you levels are not dropping too low during your cat’s lowest points of the day.
  • If positive ketones are found on your test strip 3 days in a row, contact your veterinarian.
  • When a maintenance dose is established, continue to monitor with urine test strips weekly and note any other changes in thirst or urination, other symptoms of DM.  


Blood testing at home might be easier than you think. Home blood testing is generally more accurate than the same testing done in a veterinary clinic because blood glucose may change considerably with the stress of the trip to the vet. In some kitties, it is easier than trying to get that elusive urine sample. Lancets or small needles are used to prick the ear vein or that tiny drop of blood. There are many home use glucometers available. 

Check out for some excellent pointers and for an actual video.

In the early stages of regulating your cat’s insulin dose, keep a chart of glucose levels including time taken, amount of food eaten, and any pertinent behavior patterns that follow. Good times to check blood glucose are just before injecting insulin and about 4 to 6 hours later, when it should have its peak effect. With blood testing, you can detect both high and the dangerously low glucose levels.

  • Begin with the insulin dose determined by your veterinarian and continue at that dose for a week to 10 days even if blood glucose remains high. 
  • Then, if glucose has remained high (above 300) raise dose by ½ unit on a day when you can be home to observe your cat. Report new dose to your veterinarian. Check blood glucose just before injection and 4 to 6 hours later. Continue 5 to 7 days at this dose. 
  • Continue increasing by ½ unit per week or two until, ideally, glucose levels remain between 70 and 250. Report each dose change to your veterinarian. 

Fructosamine testing at your veterinarian’s office one to four times per year gives you a long term view of how well your cat’s DM has been controlled over time.

Continuous glucose monitoring systems are high tech (and around $1000). Medtronic makes the Guardian RT that displays glucose levels every 5 minutes on a small monitor that can be attached to kitty’s collar. An implanted wireless sensor transmits this information and it can be downloaded to a computer to make an elaborate glucose curve printout. 


TOO HIGH:  If your cat’s blood glucose levels continually test high, work with your veterinarian to increase insulin dosages slowly. Uncontrolled DM results in kidney failure, cataracts, heart disease, emaciation, and other life-threatening metabolic changes. Insulin demand may increase with weight gain, age, inappropriate diet, or sometimes because your cat’s immune system begins to attack the injected insulin as a foreign substance.

TOO LOW:  Too rapid insulin increases can sometimes overshoot actual insulin need. This can result in an odd mechanism, the Somogyi effect, where the stress of prolonged low blood glucose causes the body to create an emergency high blood glucose response. By checking blood glucose at that moment in time, it can easily be misinterpreted as a need for even higher insulin levels until the cat’s whole system collapses.

Keep excellent records of insulin dosages and glucose readings to help make dose change decisions. Even after you think you have found the magic number that keeps your cat perfectly tuned, weight loss or healthier eating habits may lower the dose or occasionally even eliminate the need for insulin injections. Weight gain and other health issues may increase your cat’s insulin needs. 

Owners of cats on insulin need to beware of the diabetic “crash” or excessively low blood glucose. Some cats, especially after correction of obesity, may totally “outgrow” their need for insulin and can be managed by proper feeding alone. Many things can lower the need for insulin:

  • Suddenly decreased appetite or change in nutrient content of food
  • Increased exercise
  • Changes in other metabolic diseases
  • Other illness, infections, and treatment (bladder infections are common causes of fluctuations)
  • Weight loss

Blood glucose is the fuel going to the cells to keep them functioning. When glucose levels drop too low, cells and then systems begin to fail and we see:

  • Behavioral changes
  • Weakness and depression
  • Anxiety, muscle twitching
  • Seizures
  • Coma leading to death


  • Keep white corn syrup on hand.
  • If your cat is showing mild symptoms and you are capable of home blood testing, sample your cat before treating to confirm your suspicions. 
  • If symptoms are more severe, even if your pet is in a coma, rub a little corn syrup into his mouth with your finger. (Do not use large volumes because your cat may not be able to swallow.)
  • Contact your veterinarian.
  • If help is far away, repeat the corn syrup as needed until your cat is able to swallow. Offer kitty’s favorite food and encourage eating.
  • Speak to your veterinarian before giving the next dose of insulin.