This handout provides detailed information on how to give insulin. For more information about diabetes mellitus, see the handouts "Diabetes Mellitus in Cats: Overview", and "Diabetes Mellitus: Principles of Treatment in Cats".
What is diabetes mellitus?
Diabetes mellitus is a failure of the body to regulate blood sugar levels. In cats, diabetes mellitus is most often type II diabetes, which means insulin is still being produced, but there isn’t enough, or the cells don’t respond to it appropriately (insulin resistance). Type II diabetes usually results from obesity, which creates insulin resistance. Most cats need insulin injections to stabilize their blood sugar, although some cats no longer need these injections if they can achieve a normal body weight.
What do I need to know about insulin treatment for diabetes mellitus?
Many diabetic cats need insulin injections to regulate their blood glucose, at least initially. There are newer oral medications that may achieve glucose stabilization; however, they currently aren’t recommended for all cats. Cats with diabetes mellitus typically require one or two daily insulin injections as well as a dietary change. Dietary change is critical in obese cats to combat insulin resistance and to allow the insulin to be effective. Insulin treatment should be part of the cat's daily routine, which means that you, as the cat's owner, must make both a financial commitment and a personal commitment to treat your cat. If you are out of town or go on vacation, your cat must receive proper treatment in your absence.
Initially, your cat may be hospitalized for a few days to deal with any immediate crisis and to begin the insulin regulation process. For instance, if your cat is so sick that he has stopped eating and drinking for several days, he may be experiencing diabetic ketoacidosis (DKA), which may require several days of intensive care.
Once your cat is home, you will continue to administer insulin as prescribed. Blood sugar (glucose) trends can be tracked easily with a home glucose monitoring unit (glucometer) such as the AlphaTrak®2, or a continuous glucose monitoring (CGM) system (Freestyle Libre®). Your veterinary healthcare team will place the CGM monitor or teach you how to take the tiny blood sample needed for the glucometer to check your cat's glucose levels.
Glucose readings taken at home, in your cat's natural environment, are generally more accurate because stress levels are low. At first, regular glucose readings will be required to monitor progress. It may take a month or more to achieve good insulin regulation. Your veterinarian will work with you to achieve consistent regulation, but some cats are difficult to regulate or keep regulated. The most used insulins are ProZinc®, glargine, and Vetsulin® (known as Caninsulin® in Canada). Your veterinarian will determine the best insulin for your cat. You may need to switch between different types of insulin if your cat is not achieving adequate glucose control.
"You may need to switch between different types of insulin if your cat is not achieving adequate glucose control."
Many people are fearful of inflicting pain or harm by giving insulin injections. This fear is unfounded, because the disposable injection needles are extremely sharp and cause minimal pain. The insulin does not sting when it’s injected and injections are given under the skin in areas where it is impossible to damage internal structures. Some insulins (Vetsulin® and glargine) are available in “pen” form and may be easier to administer. Once you are coached on how to give them, you may be pleasantly surprised at how easy it is and how well your cat tolerates the injections.
As well as diet, consistent treatment is a vital component of the proper management of the diabetic cat. Your cat needs consistent administration of insulin, consistent feeding of a recommended diet to achieve an ideal body weight, and a stable, stress-free lifestyle. Your cat should live indoors to minimize uncontrollable variables that can disrupt regulation.
How is insulin stored?
Insulin is a hormone that will lose its effectiveness if exposed to direct sunlight or high temperatures. It should be kept in the refrigerator, but it should not be frozen. If you have any doubt about the storage of your cat's insulin, it is safer to replace it rather than risk using ineffective insulin. Insulin is safe if it is used as directed. Keep it out of reach of children.
Insulin comes in an airtight bottle that is labeled with the insulin type and the concentration. It is important to make sure you match the insulin concentration with the proper insulin needles. Insulin needles show their measurement in "units per mL", which must correspond to the concentration of the insulin you are using. There are two common forms of insulin and corresponding syringes: U-100 and U-40. Your veterinarian will instruct you on which type of insulin you are using and which type of syringe you should use.
How should I draw up the insulin?
Insulin is a suspension not a solution, so before administering it you must mix it. Some insulins should be gently rolled and not shaken, while others should be shaken thoroughly. Your veterinarian will advise you on how to handle the insulin. Some insulin has a tendency to settle out of suspension, so mixing is very important for accurate dosing.
The trick is to mix it vigorously enough to blend it without creating foam. When you have finished mixing the insulin, turn the bottle upside down to see if any of the white insulin molecules still adhere to the bottom of the bottle. If so, more mixing is needed.
Get the needle and syringe, insulin bottle, and cat ready. Then, follow these steps:
- Remove the cap from the needle and draw back the plunger to the appropriate dose.
- After mixing the insulin, carefully insert the needle into the insulin bottle.
- Inject the air from the syringe into the bottle. Before drawing out insulin, it is best to inject the same amount of air into the bottle to maintain normal pressure.
- Draw out more insulin than you need, then inject the excess back into the bottle. This helps to remove any air bubbles from the syringe. Measure the dose at the edge of the plunger that is closest to the needle.
How do I inject the insulin?
Generally, you will inject insulin as the cat is eating his meal, because it is critical that insulin be given with a meal. Some cats need a second person to hold them steady initially.
- Hold the syringe like you would hold a pen or pencil when you prepare to write.
- Have someone hold or distract your cat while you lift a stretchy area of your cat’s skin. It’s often easiest to use the skin over the shoulders, but it is best if you use different sites around the body.
- Quickly push the sharp, thin needle through your cat's skin at about a 45-degree angle into the space or “tent” produced by lifting the skin and push the syringe plunger all the way into the syringe barrel.
- Withdraw the syringe and needle. If you are unsure if you administered it correctly, or if you “missed,” do not administer additional insulin. Simply resume your normal schedule and give the next insulin injection at the regular time.
- Immediately and carefully place the uncapped needle and syringe into a puncture-resistant container (e.g., a sharps container). Do not leave a needle and syringe anywhere it can injure your pet or yourself. Most communities have strict rules about disposal of medical waste, so do not throw the needle and syringe into the garbage unless you know it is permissible. It is better to take the used needles and syringes to your veterinary clinic or local pharmacy for disposal.
- Stroke and praise your cat to reward him for sitting quietly.
Should I sterilize the skin with alcohol before giving the injection?
No, do not swab the skin with alcohol to “sterilize” it. There are several reasons:
- The smell of alcohol can make your cat dislike the injections.
- Brief swabbing with alcohol or any other antiseptic does not effectively sterilize the skin, due to the nature of the hair coat and the type of bacteria that live near cats’ skin.
- The needle may carry a small amount of alcohol through the skin, and it may carry bacteria with it.
- Alcohol makes the skin or hair wet, so you can’t see if you have accidentally injected insulin onto the surface of the skin. If you do not use alcohol, wet hair or skin following an injection clearly indicates that the injection was not done properly.
Although the above procedures may at first seem complicated and somewhat overwhelming, they will quickly become second nature. Your cat will soon learn that, once or twice each day, he must sit still for a few moments. In most cases, a reward of food or stroking results in a fully cooperative cat that eventually may not even need to be held.
Does hypoglycemia occur in cats?
Hypoglycemia means low blood sugar. If the blood sugar falls below 40 mg/dl (2.2 mmol/L), it can be life-threatening. Hypoglycemia generally occurs under two conditions:
- The insulin dose is too high. Many cats require the same dose of insulin for a long time, but the cat’s insulin requirements may suddenly change, especially if they reach their ideal body weight, reduce their food intake, or increase their exercise or activity. Your cat should eat before you give an insulin injection, because once the insulin is administered, it cannot be removed from the body. If your cat does not eat, or if only half of the food is eaten, give only a half half-dose of insulin. If this happens more than once, take your cat to the veterinarian for assessment. Remember that it is always better in the short term for blood sugar to be too high than too low.
- Too much insulin is given. This can occur because the insulin was not properly measured in the syringe or because two doses were given. Place a chart in a central location to record insulin administration and prevent the cat being treated twice.
A cat is most likely to become hypoglycemic at the time of peak insulin effect: 5–8 hours after an insulin injection. When the blood glucose is only mildly low, your cat will act very tired and will be unresponsive. They may appear wobbly or unsteady on their feet. When you call your cat, you may get little or no response. Usually, 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 any subtle signs of hypoglycemia because it is the first sign of impending problems. If you see signs, take a glucose reading and call your veterinarian (or local veterinary emergency hospital if it is after hours). Your veterinarian may have you offer an extra meal and recheck the glucose level a short time after your cat eats.
If severe hypoglycemia occurs, it is a true emergency, as a cat may have seizures or lose consciousness. Ultimately, untreated hypoglycemia leads to coma and death. This emergency can only be reversed with intravenous administration of glucose. If it occurs during office hours, take your cat to your veterinarian's office immediately. If it occurs at night or on the weekend, call your veterinarian's emergency phone number for instructions. A sugar syrup, such as maple syrup or corn syrup, can be applied to the gums as you are getting your cat to the veterinarian.
Summary of Instructions for Insulin Treatment of Your Cat
Read and re-read this material so you understand how to regulate your cat’s glucose and how to recognize and treat hypoglycemia.
Purchase the treatment supplies. Your prescription will specify the type of insulin and syringes as well as the appropriate home glucose monitoring device and test strips. Note that you cannot use another brand of test strips in the animal-approved glucose meter.[MY6] [KW7] [MY8]
Type of insulin: ______________________________________
Type of insulin syringes: U-100 U-40
Give the first injection of insulin of ____________ units at about ____________ AM / PM.
If your cat shows symptoms of low blood sugar, give ______ tbsp ( ______ mL) of corn syrup, based on your cat's body weight of ______ lbs (______ kg).
