Mar Vista Animal Medical Center

3850 Grand View Blvd.
Los Angeles, CA 90066






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Insulin is the injectable medication you will be using to control your diabetic dog’s blood sugar. As 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 very 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 10-24 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 (click here for more information) but if you are a beginner you may want to master giving the injections before moving on to actually taking blood samples.

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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 modiied human insulin (produced through genetic engineering technology) but seems to work well in dogs. In addition to these two insulins, ProZinc® insulin, a popular human origin insulin mostly used for diabetic cats, has been approved for canine use so its use is likely to become more frequent. There are other types of insulins but as these are rarely used in dogs, probably will not come up except for special circumstances so they are omitted from this discussion.

Vetsulin and ProZinc insulin are 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.

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Insulin pens
(Photocredit: Public Domain image via Wikimedia Commons)





The bottle you are currently using need not be refrigerated though 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. In fact, it is a good idea to change to a fresh bottle every 6-8 weeks.
  • 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.



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 of the dog so let your veterinarian know if you would like a small spot shaved to facilitate the injection.

U-40 Insulin Syringes
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U-100 Insulin Syringes
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  • 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 such a container, the entire container can be closed up and disposed of in the regular trash at home. Special containers can be purchased for needle disposal or the used syringes can be returned to the veterinary hospital for disposal if you prefer. 



As of September 1st, 2008 it has been illegal to dispose of used sharp medical waste (syringes, needles, needle tips etc.) in the regular trash even if they are in a thick plastic container. You must instead return used sharp waste to a special disposal center or use a special “mail-in” sharps container. In California, medical wastes must go to special medical waste landfills.

For more information on what you are allowed to do: click here.


(Photocredit: Teri Ann Oursler, used with permission)

First, feed your pet. A pet that has not eaten a normal meal but receives insulin may drop his or her blood sugar to a dangerous low level. If your pet is not eating, this could indicate a need for a check up with your veterinarian. After the pet 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, the presence of bubbles is not an enormous problem (as it would be with an intravenous injection) but we still want to minimize the presence of bubbles. If you get bubbles in the syringe, flick the syringe with your fingers until the bubble rises to the top and then simply push the air out of the syringe with the plunger.

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 very rambunctious and a helper is necessary. If you have such a pet but no helper, consider tying your dog’s leash short around a piece of furniture. (Use a slip knot in case of choking emergency.) Some dogs are very uncooperative and require a muzzle.

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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.

To view this information in a video format:



An insulin pen is a gadget that allows precision insulin measurements and push button ease of administration. The arrangement 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 with each use). The dose is dialed in with accuracy up to the half unit (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 after which the needle is inserted through the pet's skin and a button at the top of the pen is pressed. The needle must stay in place at least 5 seconds to insure 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 in the refrigerator though the loaded pen may be stored in the refrigerator on its side. Most human insulin pens are disposable and cannot be reloaded. They are meant to be stored in the refrigerator until they are opened for use. After they are in use, they are meant to be kept at room temperature.

Want more information on the Vetsulin VetPen®? Watch this video:

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.



 Page last updated: 3/22/02021