Diabetes Mellitus: Insulin Treatment in Dogs

By Krista Williams, BSc, DVM; Robin Downing, DVM, DAAPM, DACVSMR, CVPP; Ernest Ward, DVM

This handout provides detailed information on insulin administration. For more information about diabetes mellitus, see the handouts "Diabetes Mellitus - Overview", and "Diabetes Mellitus - Principles of Treatment in Dogs".

What is diabetes mellitus?

In dogs, diabetes mellitus is caused by the failure of the pancreas to produce enough insulin to regulate blood sugar. This is insulin-dependent diabetes mellitus (also called Type 1 Diabetes). This type of diabetes usually results from destruction of most or all beta-cells that produce insulin in the pancreas. As the name implies, dogs with this type of diabetes require insulin injections to stabilize blood sugar levels.

What do I need to know about insulin treatment for diabetes mellitus?

In diabetic dogs, the main treatment for regulating blood glucose is giving insulin by injection. Dogs with diabetes mellitus typically require two daily insulin injections, as well as a dietary change. Although a dog can go a day or so without insulin and not have a crisis, this should not be a regular occurrence; treatment should be looked upon as part of the dog's daily routine. This means that you, as the dog's owner, must make both a financial commitment and a personal commitment to treat your dog. If you are out of town or go on vacation, your dog must receive proper treatment while you’re away.

Initially, your dog may be hospitalized for a few days to deal with any immediate crisis and to begin the insulin regulation process. For instance, if your dog is so sick that he has stopped eating and drinking for several days, he may be experiencing diabetic ketoacidosis, which may require several days of intensive care.

Once your dog is home, you will continue to administer insulin as prescribed. You can easily track blood sugar (glucose) levels with a home monitoring unit such as the AlphaTrak®2, or Freestyle Libre®. Because the glucose readings are taken at home in your dog's natural environment, stress levels are low, and the readings are more generally more accurate. 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 try to achieve consistent regulation, but some dogs are difficult to keep regulated.

"You can easily track blood sugar (glucose) levels with a home monitoring unit such as the AlphaTrak®2, or Freestyle Libre®."

Consistent treatment is a vital part of the proper management of a diabetic dog. Your dog needs consistent administration of insulin, consistent feeding, and a stable, stress-free lifestyle. Your dog should live indoors to minimize uncontrollable variables that can disrupt regulation. The most used insulins are Vetsulin®/Caninsulin®, Humulin®N, and Detemir (brand name Levemir®). Other available insulins include Glargine (Lantus®) and Protamine Zinc (ProZinc®). Your veterinarian will determine the best insulin for your dog.

Many people are afraid of inflicting pain or harm by giving insulin injections. This fear is unfounded, since the disposable injection needles are extremely sharp and cause minimal pain. The insulin does not sting on injection and the injections are given under the skin in areas where it is impossible to damage internal structures. Some insulins (Vetsulin®) 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 dog tolerates the injections.

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 dog'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.

"It is important to make sure you match the insulin concentration with the proper insulin needles."

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, syringe, insulin bottle, and dog ready. Then, follow these steps:

  1. Remove the cap from the needle and draw back the plunger to the appropriate dose.
  2. After mixing the insulin, carefully insert the needle into the insulin bottle.
  3. 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. 
  4. 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 dog is eating her meal, because it is critical that insulin be given with a meal. Some dogs need a second person to hold them steady initially.

  1. Hold the syringe like you would hold a pen or pencil when you prepare to write.
  2. Have someone hold your dog while you lift a stretchy area of your dog’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.
  3. Quickly push the sharp, thin needle through your dog'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.
  4. 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.
  5. 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.
  6. Stroke and praise your dog 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 the alcohol can make your dog dislike the injections.
  • Brief swabbing with alcohol or any other antiseptic does not effectively sterilize the skin, due to the nature of the thick hair coat and the type of bacteria that live near dogs’ 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 won’t be able to 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 dog will soon learn that, once or twice each day, he must sit still for a few moments. In most cases, a reward of stroking results in a fully cooperative dog that eventually may not even need to be held.

Does hypoglycemia occur in dogs?

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:

  1. The insulin dose is too high. Most dogs require the same dose of insulin for a long time, but the dog's insulin requirements may suddenly change. The most common cause is reduced food intake or increased exercise or activity. Your dog should eat before you give an insulin injection, because once the insulin is administered, it cannot be removed from the body. If your dog does not eat, or if only half of the food is eaten, give only a half dose of insulin. If this happens more than once, take your dog to the veterinarian for assessment. Remember it is always better in the short term for the blood sugar to be too high than too low.
  2. 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 dog being treated twice.

The most likely time that a dog 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 dog will act very tired and will be unresponsive. When you call your dog, you may get little or no reaction. Within a few hours, the blood glucose will rise, and your dog will return to normal. Since many dogs 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 the dog eats.

If severe hypoglycemia occurs, this is a true emergency as a dog 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 dog 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 dog to the veterinarian.

Summary of Instructions for Insulin Treatment of Your Dog

Read and re-read this material so that you understand the specifics of proper regulation and how to recognize and treat hypoglycemia.

Purchase the supplies for treatment. Your prescription will specify the type of insulin and syringes, as well as the appropriate home glucose monitoring device and test strips. Your veterinarian will recommend the glucometer or continuous glucose monitoring system that is best for your pet and can coach you on how to use these items to monitor your dog’s blood sugar levels. You cannot use another brand of test strips in the animal-approved glucose meter.

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 dog shows symptoms of low blood sugar, give ______ tbsp ( ______ mL) of corn syrup, based on your dog's body weight of ______ lbs (______ kg).

Your veterinarian will let you know how often to perform a glucose curve at home. Generally, the first glucose curve is performed 7 to 14 days after beginning insulin therapy, but you may need to take a few readings each day. When performing a curve, you will take blood glucose readings every 1 to 2 hours for 12 hours (the time between insulin injections). You will then contact the veterinary practice with the curve values so that they may fine-tune the insulin dose.

Return to the practice for a glucose curve as prescribed, no later than ____________ a.m., on________________________.

Feed your dog that morning and immediately take him to the hospital. Do not give insulin but bring it with you. If it takes more than 30 minutes to drive to the hospital, call for instructions on feeding. In-hospital glucose curves may not be needed, depending on how easily your dog's glucose levels are stabilized.

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