College of Veterinary Medicine

Pet Health Topics

Diabetes mellitus  

This information is not meant to be a substitute for veterinary care. Always follow the instructions provided by your veterinarian.

Diabetes mellitus occurs when the pancreas doesn't  produce enough insulin. Insulin is required for the body to efficiently use sugars, fats and proteins. 

Diabetes most commonly occurs in middle age to older dogs and cats, but occasionally occurs in young animals. When diabetes occurs in young animals, it is often genetic and may occur in related animals. Diabetes mellitus occurs more commonly in female dogs and in male cats. 

Certain conditions predispose a dog or cat to developing diabetes. Animals that are overweight or those with inflammation of the pancreas are predisposed to developing diabetes. Some drugs can interfere with insulin, leading to diabetes. Glucocorticoids, which are cortisone-type drugs, and hormones used for heat control are drugs that are most likely to cause diabetes.  These are commonly used drugs and only a small percentage of animals receiving these drugs develop diabetes after long term use.

The body needs insulin to use sugar, fat and protein from the diet for energy. Without insulin, sugar accumulates in the blood and spills into the urine.  Sugar in the urine causes the pet to pass large amounts of urine and to drink lots of water. Levels of  sugar in the brain control appetite. Without insulin, the brain becomes sugar deprived and the animal is constantly hungry, yet they may lose weight due to improper use of nutrients from the diet. Untreated diabetic pets are more likely to develop infections and commonly get bladder, kidney, or skin infections. Diabetic dogs, and rarely cats, can develop cataracts in the eyes. Cataracts are caused by the accumulation of water in the lens and can lead to blindness. Fat accumulates in the liver of animals with diabetes. Less common signs of diabetes are weakness or abnormal gait due to nerve or muscle dysfunction.  There are two major forms of diabetes in the dog and cat: 1) uncomplicated diabetes and 2) diabetes with ketoacidosis. Pets with uncomplicated diabetes may have the signs just described but are not extremely ill.  Diabetic pets with ketoacidosis are very ill and may be vomiting and depressed.

The diagnosis of diabetes is made by finding a large increase in blood sugar and a large amount of sugar in the urine. Animals, especially cats, stressed by having a blood sample drawn, can have a temporary increase in blood sugar, but there is no sugar in the urine.  A blood screen of other organs is obtained to look for changes in the liver, kidney and pancreas. A urine sample may be cultured to look for infection of the kidneys or bladder. Diabetic patients with ketoacidosis may have an elevation of waste products that are normally removed by the kidneys.

The treatment is different for patients with uncomplicated diabetes and those with ketoacidosis.  Ketoacidotic diabetics are treated with intravenous fluids and rapid acting insulin.  This treatment is continued until the pet is no longer vomiting and is eating, then the treatment is the same as for uncomplicated diabetes.

bottle of insulin and inset picture of aluminum ring rubber stopper labeled on the bottle top

the inset picture shows the top of the insulin bottle

Diabetes is managed long term by the injection of  insulin by the owner once or twice a day. Some diabetic cats can be treated with oral medications instead of insulin injections, but the oral medications are rarely effective in the dog. There are three general types of insulin used in dogs and cats:

  • short- acting insulin (regular or crystalline) is used in sick diabetic animals until they are eating again 
  • NPH and Lente are intermediate- acting insulins 
  • Ultralente and PZI are long- acting insulins
  Insulin comes from different sources including beef or pork pancreas and a human genetically engineered form called Humulin.  The availability of animal-source insulins continues to decline.

In general, cats and small dogs need insulin injections more frequently, usually twice daily, compared to large breed dogs that may only require one dose of insulin daily. The action of insulin varies in each individual and some large dogs will need 2 insulin shots daily.  The insulin needs of the individual animal are determined by collecting small amounts of blood for glucose (sugar) levels every 1-2 hours for 12-24 hours. This is called an insulin-glucose-response curve. When insulin treatment is first begun,  it is often  necessary to perform several insulin-glucose-response curves to determine:

  • which insulin type to use
  • how much insulin to give
  • how often to give insulin
  • when is the best time to feed the animal

The animal's insulin needs may change over time requiring a change in insulin type or frequency of injection. Insulin- glucose- response curves are usually performed several days after a change in insulin is made.

  Before you give insulin injections to your pet, your veterinarian will show you how to:

  • handle insulin
  • use a syringe
  • draw insulin from the bottle in the correct amount
  • give your pet the insulin shot

Insulin is fragile and will become less effective or even inactive, if it gets too hot or cold, or is shaken vigorously. Pay attention to the expiration date on the bottle. Discard insulin that is outdated.

You may be able to practice using water and giving the "shot" to an object such as a piece of fruit until you are comfortable using needles, syringes and drawing accurate amounts of fluid into a syringe. 

30 unit and 100 unit syringes

Not all syringes used to inject insulin are alike. When you buy additional supplies, make sure that you buy the right kind of syringes. Insulin needles are very thin to reduce discomfort during injection.


Insulin syringes can fill to hold:

  • 30 units
  • 50 units
  • 100 units
sterile syringe needle packaged in a plastic case The syringe is packaged in sterile paper or plastic wrapping or in a plastic case. The needle is covered with a plastic cap to keep it sterile. Use a new syringe-needle combination for each injection. 

labeled parts of a syringe and its packaging

Insulin syringes have the needle attached. The needle is covered with a plastic cap to prevent the needle from puncturing the wrapping and to keep the needle from bending or breaking. 

Remove the syringe and needle from the outer wrapping. Do not remove the needle cap until you are ready to draw insulin into the syringe. 



labeled parts of a syringe The plunger fits inside the hollow barrel of the syringe and is pulled part way out of the barrel to draw insulin into the syringe. The plunger is pushed into the barrel of the syringe to push insulin through the needle. The finger grip makes it easier to hold the syringe. 
the barrel and removed plunger of a syringe
30 unit syringe with 5 unit increments and a 100 unit syringe with 10 unit increments

100 unit syringes are numbered by 10's; 10, 20, 30, etc. 

The smallest lines between the numbers on a 100 unit syringe, measure 2 units of insulin. 

30 unit syringes are numbered by 5's; 5, 10 , 15, etc. 

The smallest lines between the numbers on a 30 unit syringe, measure 1 unit of insulin. 

correct way to read the volume of insulin in the syringe The position of the TOP of the black rubber stopper on the plunger is used to measure the volume of insulin in the syringe. The TOP of the black rubber stopper is the part closest to the needle.
rolling the insulin bottle between the palm of your hands Before each injection,

The insulin bottle should not be shaken but rather gently rolled between your hands to mix the insulin in the bottle.

using one hand to hold the syringe and pull the plunger Remove the plastic cap from the needle. 

Hold the syringe between the thumb and index finger.

Pull back on the plunger to the desired dose level drawing some air into the syringe.

You can either pull back the plunger using the middle finger of the hand holding the syringe or...

using one hand to hold the syringe, and the other to pull the plunger

Hold the syringe in your left hand between the thumb and index finger and use the thumb and index finger of the other hand to pull the plunger or...

pulling the plunger with one hand while bracing your index finger against the finger grip

Place your index finger against the finger grip and pull the plunger with your thumb and middle fingers.
using two hands to insert the syringe into the upside down insulin bottle Hold the insulin bottle upside down in your left hand if you are right handed (opposite for left-handed individuals). 

Place the needle in the center of the rubber stopper. If the needle is not centered you may be trying to force the needle through the metal ring that is holding the rubber stopper in place and will break the needle.

injecting air into the bottle Use your thumb to push the plunger and inject the air into the bottle. 

The air is placed in the bottle so a vacuum does not form in the bottle which makes it more difficult to draw insulin from the bottle.


inserting the needle the correct distance into the insulin bottle

Insert the entire length of the needle into the insulin bottle as long as the tip of the needle is in the fluid in the bottle. Insulin needles are very thin and easily bent. You are less likely to bend the needle while drawing insulin into the syringe, if the needle is inserted all the way into the bottle. 

If there is only a small amount of insulin left in the bottle, you may only be able to insert the needle into the bottle part way or else you will pass through the fluid and into the air in the bottle.

Draw back on the plunger to the correct dose using your middle finger to pull back the plunger.

trapping the syringe against your palm, and pulling back the syringe If it is difficult for you to pull the plunger with your middle finger, you can use the thumb and index finger to pull the plunger. So that you do not pull the needle out of the bottle, curl the three fingers of your right hand that are not holding the bottle around the syringe trapping it against your palm. Then pull the plunger with the thumb and index finger. Your fingers may be covering the numbers on the syringe so draw more than you need, then push the extra back into the bottle, until the correct amount remains in the syringe.

placing your index finger against the finger grip while using your thumb and middle fingers to pull back the plunger

...or place your index finger against the finger grip to keep the needle from pulling out of the bottle and pull the plunger with your thumb and middle fingers.
tapping the syringe If there is an air bubble in the syringe, draw a little more insulin than the correct dose. 

Remove the syringe and needle from the insulin bottle. Holding the syringe with the needle pointed up, gently "flick" the syringe to get the air to rise to the top.

pressing the plunger to remove air Press the plunger with your thumb to push the air out of the syringe, until the correct amount of insulin remains in the syringe.
30 unit syringe filled to 14.5 units This 30 unit syringe has been filled to 14.5 units. 

close up of black rubber stopper and units on syringe

There is 1 unit between each back line on this smaller syringe. Smaller syringes allow for more accurate measurements of small amounts of insulin. The top of the black rubber stopper is half way between 14 and 15 units.

100 unit syringe filled to 48 units

This 100 unit syringe has been filled to 48 units. There are 2 units between each black line on the barrel. The volume is measured at the TOP of the black rubber stopper on the plunger.
closeup of syringe with top and bottom of stopper labeled
correctly pinching a fold of the cats skin and inserting the needle

Pinch up a fold of skin anywhere along the neck or back using your left hand if you are right-handed. Use your right hand to place the needle into the skin fold along the long axis of the fold. 

Usually the skin is not cleansed before inserting the needle. If the cat has a normal immune system, the few bacteria that are pushed under the skin with the needle will be killed by the cat's immune system.

You can use alcohol on a cotton ball to make the hair lay flat so it is easier to see where the hair ends and the skin starts. Alcohol takes about 30 minutes before bacteria are killed, so just swiping the hair with alcohol is not effective in killing bacteria.

placing the needle across the skin fold, in the opposite direction If you place the needle in the opposite direction, across the skin fold, it is more likely that the needle will go through one fold of skin and out the other fold of skin, or may poke into your finger.
checking for correct placement of needle

Pull back the plunger. If you get air, you placed the needle through both folds of skin. Remove the needle and try again. If you get blood, the tip of the needle is in a blood vessel. Remove the needle and try again.

If you get neither air nor blood, the needle is placed correctly and you can push the plunger to inject the insulin.

Give the insulin shots in different locations each time.

Syringes and needles used to give insulin should not be discarded in the trash but should be placed in a puncture-proof container and taken to your veterinarian for disposal. 

Insulin injections are not as perfect as the insulin produced by the pancreas. Blood sugar levels will not always be normal in diabetic pets. The goal of treatment is to reduce the  signs of diabetes. When diabetes is well controlled with insulin, the pet should drink, eat and urinate normal amounts.  They should have a good appetite, without becoming fat and should have normal activity. 

Insulin needs are closely related to the type of  food eaten by the pet. Your veterinarian will recommend a specific diet and feeding regimen that will enhance the effectiveness of insulin. If your pet is overweight, s(he) will be placed on a weight-reducing diet. As the pet loses weight, less insulin will be needed. Only feed the recommended diet..NO table scraps or treats that are not part of the recommended diet.

Heavy exercise will reduce the amount of insulin needed. It is important  to talk to your veterinarian before making changes in diet or exercise.

There is always some risk that a diabetic patient will develop low blood sugar. Signs of low blood sugar include weakness, staggering, seizures, or just being more quiet than usual. You should keep corn syrup on hand to rub on the animals gums if they have signs suggestive of low blood sugar.  Don't pour large amounts of corn syrup in the mouth of an animal that is not fully conscious as the syrup may be inhaled into the lungs.

Because insulin needs vary with the activity and lifestyle of your pet, you may want to keep a written daily log of:

  • the dose of insulin
  • location in which the insulin is injected
  • any changes in the pet’s activity or appetite

Your veterinarian may ask you to check your pet's urine for sugar using a test strip. If your pet is well regulated on insulin, the sugar readings in most urine samples will be negative or trace. The strips may have color pads only for glucose or for glucose and ketones.

ketose and glucose strip colors and what they mean

The strip is placed in fresh urine and the color change compared with the colors on the bottle. Be sure to follow the label instructions for timing when to read the results.  

reading the urine sugar strip The top color pad is to read urine sugar. This sample is negative for sugar. The bottom color pad is for ketones and is also negative for ketones.
reading the strip for the level of ketones in the urine The glucose pad has turned brown indicating a large amount (>2000mg/dl) of sugar in the urine. The urine is negative for ketones.

You should never change the dose of insulin based on the urine sugar reading alone. Animals can have lots of sugar in their urine either when the insulin dose is too low or is too high.   

a glucometer If your pet is difficult to regulate with the proper dose of insulin you may be taught how to take a small blood sample from your pet to measure blood sugar readings at home.

There are many styles of machines used to measure blood sugar. The machines are called glucometers. They use color sticks which are read by the glucometer rather than by color changes you can see. Different styles of glucometers use different color strips.

Diabetes is rarely reversible in dogs, but diabetic cats will sometimes regain the ability to produce their own insulin in the pancreas. Cats that developed diabetes after receiving long term glucocorticoids or hormones are more likely to stop needing insulin after a while compared to cats that developed diabetes without a known cause. 

You should have your diabetic pet evaluated by a veterinarian at 2-4 month intervals or anytime another health problem develops. The development of other health problems will often interfere with insulin regulation.


Washington State University assumes no liability for injury to you or your pet incurred by following these descriptions or procedures.

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Last Edited: Jan 08, 2016 11:07 AM   

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