Recap: Insulin

Posted by Michelle for PetTest, AAHA Certified Diabetes Educator on Aug 17th 2021

Recap: Insulin

I know that I have already written about insulin, but with so many new members in our Facebook group Diabetic Dog Owners and a slew of questions about different types of insulin I felt it important to write a recap.

When Lucy was diagnosed with diabetes and pancreatitis I was given quick instruction on how to prepare Vetsulin and administer a dose. What I was not told was that Vetsulin needed to be shaken to mix properly. I rolled it gently the first couple of months until I was notified to shake it, and then I grabbed the insert and read instructions…YEP YOU SHAKE IT! I promptly informed my vet that Vetsulin is to be shaken, not gently rolled like other insulins.

Lucy did not do very well on Vetsulin and when I spoke to my vet about switching insulin types, he mentioned Humulin N as an option but also told me it was $150 per vial. I was flabbergasted! I did a bit more research and found that Novolin N is the same type of insulin as Humulin N and when purchased at Walmart in the USA, Novolin N is $24.88. So back to the vet I went and had him write a prescription for Novolin N.  I will be honest; I was a bit nervous switching insulin types. However, once I did and got Lucy's blood glucose in target range I felt like I had won the world!

Grab a cup of your favorite caffeine beverage and let’s go over the different types of insulin we commonly give our dogs!

Vetsulin Caninsulin for PT Blog mtm

  • Lente insulin, combination insulin (65/35 in USA & Canada, 70/30 elsewhere)
  • Must be shaken, milky in appearance once mixed.
  • Store in the refrigerator at 36° - 46° F (2.22° - 7.78° C), keep away from sunlight.
  • Discard 42 days post puncture
  • Two peaks: 2 - 6 hrs. & 8 - 14 hrs.
  • Duration - 12 hours
  • /
  • U40 insulin - use U40 syringes

NPH Insulin for PT Blog mtm

  • NPH type insulin; Intermediate acting insulin; this is a human insulin.
  • Must be gently rolled, milky in appearance once mixed.
  • Store opened bottle below 77° F (25° C), keep away from sunlight.
  • Humulin N: Discard 31 days post puncture for vials, KwikPen discard after 14 days.
  • Novolin N: Discard 42 days post puncture for vials, pen fills discard after 28 days.
  • One peak - 4 - 6 hrs.
  • Duration - 12 hours.
  • U100 insulin - use U100 syringes


Vetsulin / Caninsulin was introduced for dogs in 2004 by Merck Animal Health. The original formula was a 70/30 mixture, 70% was crystalline insulin and 30% was amorphous. The 30% acted like a regular type of insulin, meaning that it kicked in faster to help with food spikes. The 70% kicked in just like intermediate acting insulin and helped keep blood glucose levels lower for a longer period. In 2009 the FDA started receiving complaints regarding stability problems and in 2011 Vetsulin was taken off the market. Vetsulin was reintroduced in 2011 with some changes, the product insert for the USA and Canada now states that it is a 65/35 ratio (the rest of the world it is still 70/30). Preparation instructions were also changed to shake to mix instead of previous instructions to roll gently.

Even though the manufacturer has specific instructions printed in their product insert, vets continue to tell their clients to roll gently. This is wrong, it needs to be shaken to properly mix.

If your vet or their staff have told you to roll gently, or they have added a label to the box to roll gently, please contact Merck Animal Health. They will contact your vet with the proper preparation instructions. The instructions can also be found in the product insert.

Here is a link to the Vetsulin site:

Merck Companion Animal Technical Services – Dogs & Cats: 800-224-5318

Per the Vetsulin website Frequently Asked Questions:

(click on picture to take you to Vetsulin FAQ page)

Vetsulin FAQ for PT Blog mtm


Humulin N gained FDA approval for use in humans by Eli Lilly and Company in 1982. This was the first human recombinant DNA insulin and was originally made by Genentech.

Novolin N is also a recombinant DNA insulin and became available in 1991. Novo Nordisk is the manufacturer of Novolin N. Walmart and Novo Nordisk have a contract for Walmart to offer Novolin N under their brand name Relion and even though it may say Relion on the box it is the exact same Novolin N insulin you would purchase at any other pharmacy and pay over $150 for. Due to the contract that these two companies have, Novolin N is available at Walmart in the USA for $24.88.

Interesting Facts Genentech mtm

MAKE SURE YOU USE THE CORRECT SYRINGES! Vetsulin/Caninsulin is a U40 insulin, it has 40 parts of insulin per 1 mL. NPH insulin is a U100 insulin, it has 100 parts of insulin per 1 mL. This means that they are different strengths and require the appropriate syringe.

I hope you feel a little more educated about these most used types of insulin for our sweet pups. Remember, knowledge is power and education is the key to successfully managing canine diabetes!

Until next week, stay cool and caffeinated!

If you have any questions, comments or suggestions, please start a conversation below.

If you are looking for a Facebook community to join for support, I have proudly been an admin in Diabetic Dog Owners for four and a half years. You can also join Canine Diabetes Support and Information on Facebook as well.

Be sure to join the PetTest family on Facebook and Instagram. PetTest has fun, interactive posts AND they have fabulous giveaways every week!

For a printable version of this blog click here.