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Insulin Administration in Dogs

Date Published: 02/09/2010
Date Reviewed/Revised: 01/19/2021

Insulin is the injectable medication you use to control your diabetic dog’s blood sugar. When insulin therapy is started, the optimal dose for your pet is unknown and will have to be determined by trial and error.

Most dogs will need insulin injections twice a day, though occasionally a patient is found where a single dose is long acting and once-a-day insulin works out. A dose will be selected based on what research has shown to be a good starting point, and after a couple of weeks your dog will return for a glucose curve where blood sugar levels will be mapped out over the course of a 10 to 24 hour period. The curve will show if the insulin is lasting long enough and if the dose should be raised, lowered, or kept the same.

Alternatively, you can learn how to monitor your dog’s blood glucose levels yourself but if you are a beginner you may want to master giving the injections before moving on to taking blood samples.

There are two commonly used insulins for dogs: Vetsulin® and Humulin N®. Vetsulin is of pork origin but since pork and dog insulin are molecularly identical,  Vetsulin is canine insulin. Humulin N is modified human insulin (produced through genetic engineering technology) but seems to work well in dogs. In addition to these two insulins, ProZinc® insulin, a popular recombinant human insulin mostly used for diabetic cats, has been approved for canine use so its use is likely to become more frequent.

Vetsulin is available through your veterinarian’s office or through veterinary pharmacies, while Humulin N is available through any regular pharmacy. Both Vetsulin and Humulin N are now available in pens as well as in vials. The pen is fitted with a cartridge containing the insulin with a disposable needle tip on the end of the pen. The insulin dose is dialed in, and insulin is delivered with the press of a button. Vials still require syringes. ProZinc insulin is only available in a vial.

Be sure you understand how much insulin you are supposed to give your pet.

Do not change your pet's insulin dose without veterinary guidance.

Storing Insulin

The bottle you are currently using need not be refrigerated although if you have a supply of insulin bottles, it is probably best to refrigerate the bottles that are not in use.

  • Do not use insulin that is past its expiration date.

  • It is a good idea to change to a fresh bottle every 6 to 8 weeks. That being said, the standard in veterinary medicine is to keep it longer; 4-6 months as long as the insulin is refrigerated and not discoloured. Please consult with your veterinarian about what will work best for you and your pet.

  • Do not use insulin that has been frozen. Insulin is not normally frozen but accidents happen, especially in smaller refrigerators.

  • Do not expose insulin to direct light or heat.

Syringes for Use with Vials

Human and veterinary insulins are made at different concentrations and thus each requires its own type of syringes for proper dosing. Insulin syringes are extremely small in diameter so that injection will not be painful. It is a rare patient that objects to insulin shots per se, but some dogs resent being held still. It is crucial that the injection goes into the dog rather than into the fur so let your veterinarian know if you would like a small spot shaved to facilitate the injection.

  • Vetsulin is available at 40 units of insulin per cc and requires U-40 syringes.

  • Humulin N is available at 100 units of insulin per cc and requires U-100 syringes.

Always be sure you have the correct syringes for your insulin.

Used syringes should be placed inside a thick plastic container, such as a liquid laundry detergent bottle or similar receptacle. If the needle is enclosed in such a container, the entire container can be closed up and disposed of in the regular trash at home. Specific containers can be purchased for needle disposal or the used syringes can be returned to your veterinary hospital for disposal if you prefer. Some states, such as California, have specific regulations for disposing of sharps.

How to Give the Injections

Insulin is drawn into the syringe after holding the bottle upside down. Photo by Teri Ann Oursler, DVM

First, feed your dog.
The blood sugar of a dog that has not eaten a normal meal but receives insulin may drop to a dangerously low level. If your dog is not eating, this could indicate a need for a checkup with your veterinarian. After your dog has eaten, you are ready to give the injection.

Before drawing up the insulin, it is important to be sure that the insulin is properly mixed as some of it will settle on the bottom of the vial. The manufacturer of Vetsulin recommends simply shaking the bottle until the contents are uniformly milky. The manufacturer of Humulin recommends either rolling the bottle in the palms of your hands or turning the bottle over several times gently to mix the contents.

When drawing up the insulin, always hold the bottle vertically to avoid unnecessary bubbles in the syringe. Since insulin is being given under the skin, bubbles are not an enormous problem as it would be with an intravenous injection but we still want to minimize bubbles. If you get bubbles in the syringe, flick the syringe with your fingers until the bubbles rise to the top and then simply push the air out of the syringe with the plunger.

Photo courtesy of MarVistaVet.

After you have the insulin dose ready in the syringe, it is time to get your dog. Be sure you can trust your dog to hold reasonably still for the shot. Most dogs do not require a second person to hold them still but some dogs are rambunctious and a helper is necessary. If you have such a pet but no helper, consider tying a short leash around a piece of furniture. (Use a slip knot in case of a choking emergency.) Some dogs are uncooperative and require a muzzle.

Lift up a fold of skin, ideally along the side of the body. This will create a small space for the needle. Insert the needle into this space and inject the insulin. Withdraw the syringe and needle when you are finished.

Insulin by Pen

An insulin pen is a gadget that allows precision insulin measurements and push button ease of administration. The gadget is called a pen because it is shaped like a writing pen. A cartridge of insulin is snapped inside and a small needle tip is applied to the pen tip (a new tip should be used each time). The dose is dialed in with accuracy up to the half unit, which is much more accurate than trying to eyeball tiny doses with a syringe.  The pen is primed with a dose before it is used on the patient.  You insert the needle through the pet's skin, and then you press a button at top. The needle must stay in place at least five seconds to ensure the full dose has been delivered. Most people find this method of insulin delivery easier than using syringes.

Most human insulins are available as pens but Vetsulin® is the only veterinary insulin available as a pen.  Vetsulin pens are sold separately from their insulin cartridges. The cartridges should be stored upright though the loaded pen may be stored on its side. Most human insulin pens are disposable and cannot be reloaded. After the pens have been used the first time, they are meant to be kept at room temperature. 

Pens cannot be refrigerated without disrupting their measuring mechanism. This means that the insulin cartridge within the pen is good for about six weeks before it must be discarded and replaced. The needle's tips should be disposed of with the same precautions as for syringe disposal. See a video on how to use the insulin pen.

Giving injections and becoming comfortable with needles may seem intimidating at first but you will most likely be surprised at how easy it quickly becomes. Managing a diabetic pet is definitely a project but can be a very rewarding one. If you have any questions or problems, remember your veterinarian's office is available for demonstrations or to answer your questions as they come up.

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