Insulin therapy is the primary treatment used for diabetic dogs and cats[1], along with special diets and a good fitness regimen. Insulin is a hormone that helps lower blood sugar and use it for energy. The life of your diabetic pet depends on it. 

If your furry companion has recently been diagnosed with diabetes, its veterinarian has probably told you to refrigerate its insulin. 

Indeed, all dogs' and cats' insulins, including Vetsulin, Prozinc, Caninsulin, and others, are unstable medicines that require specific storage conditions. Learn how to properly store your pet's insulin at home to maximize its efficiency.

4AllFamily Travel Coolers for refrigerated insulin

Why must Veterinary Insulin be Refrigerated?

Human and animal insulins are similar, although the ones used for pets usually have a slower time of action and a longer duration. Whether for humans, dogs, cats, or other pets, all insulins must be kept refrigerated.

Indeed, insulin is a biological drug made from living sources. As such, it’s highly sensitive to temperature, light, and storage conditions. If not properly stored, your pet’s insulin can quickly spoil, go bad, or get contaminated. 

Related article: How to tell if insulin has gone bad?

Different insulins are available depending on each pet's situation, including veterinary products and human insulins. The most common ones for cats and dogs are Vetsulin, Prozinc, and Caninsulin, but others may be prescribed to your furry friends too. 

There are specific storage recommendations for each brand of insulin, so always read the instructions before use.

Related article: What Happens if You Miss a Dose of Insulin?

How to Store and Refrigerate Vetsulin?

Vetsulin is a lente, intermediate-acting type of insulin made from purified porcine insulin. It’s FDA-approved for diabetes management in dogs and cats. It’s available both in vials and auto-injectable pens (Vetpen). Like all insulins, Vetsulin must be refrigerated before first use and protected from heat once open. 

Does Vetsulin need to be refrigerated?

According to Merck Animal Health USA, the manufacturer of Vetsulin, Vetsulin must be refrigerated before first use.

When storing your dog or cat’s insulin in domestic fridges, make sure the temperature is set between 36°F and 46°F (2°C and 8°C) and does not fluctuate too much. Do not store near the freezer compartment, as freezing temperatures can deteriorate Vetsulin like any other type of insulin. 

How long can Vetsulin be out of the fridge? 

Once open, punctured, or taken out of the fridge, vials or pens of Vetsulin must be used within 42 days maximum. 

Meanwhile, you must keep your open Vetsulin pens or vials at room temperature (below 77° / 25°C) and protect them from exposure to heat. If you’re living in or traveling to places where the outside temperature is higher, you must use an insulin cooler to make sure your dog’s medicine stays effective and does not go bad.


4AllFamily Insulin Travel Coolers and Cooling Cases
4AllFamily’s insulin coolers are compatible with Vetsulin and other Veterinary insulins.


After 42 days out of the fridge, Vetsulin must be discarded as its efficacy isn’t guaranteed anymore.

Related article: How to Dispose of Insulin Needles, Syringes, Pens, and Vials Safely?

How long does Vetsulin last?

Like all insulins, Vetsulin has two expiration dates. When adequately stored in the fridge, it lasts until the expiration date labeled on the container.

Once out of the fridge or open, Vetsulin is only good for 42 days and will expire past that time.

What happens if Vetsulin is not refrigerated?

The insulin sold under the brand name Vetsulin starts deteriorating when not refrigeratedor once the cold chain has been broken. From that moment, the 42-days countdown begins.

For example, if you’ve left your dog’s insulin out overnight, you can still use it but within a maximum of 42 days and under the condition that you keep it protected from high heat.

How to tell if Vetsulin is bad?

Visual inspection sometimes helps tell if your dog's insulin has gone bad. Vetsulin is a clear water-like liquid. If you notice any change of color, cloudiness, clumps, strings, or frost inside, it’s gone bad.

Symptoms of hyperglycemia (high blood glucose) like increased thirst, frequent urination, weight loss, lethargy, or others may also indicate your dog’s or cat’s insulin isn’t good anymore. 

When in doubt, throw away the Vetsulin pen or vial and get a new one from the fridge. You don’t want to take any risks for your furry one!

Related article: What to do if you run out of insulin?

How to Store Prozinc Insulin for Cats and Dogs?

Prozinc is another brand of veterinary insulin often prescribed to diabetic dogs and cats. It’s a long-acting type of insulin derived from human insulin with a duration of action of 10 to 14 hours.

Unlike Vetsulin, Prozinc is only available in vials and not in injectable pens. But like Vetsulin and any other veterinary or human insulins, it must be refrigerated.



Insulin vial protectors


Protect your Vials of Veterinary insulin with 4AllFamily's Silicon Vial Sleeves

Does Prozinc need to be refrigerated? 

According to its manufacturer, Boehringer Ingelheim Vetmedica, Inc, protamine zinc recombinant human insulin (Prozinc) must be stored in the refrigerator at 36°F - 46°F (2°C - 8°C).

Freezing temperatures can damage your dog's insulin. Do not place Prozinc vials near the freezer compartment when stored in the fridge.

How long can Prozinc be unrefrigerated?

Prozinc is one of the most unstable insulins. While most veterinary and human insulins can be left out of the fridge for about a month without going bad, Prozinc must be refrigerated at all times.

It’s ok if a vial of Prozinc is left unrefrigerated for short periods of time. However, after a few hours (24 at the most), it starts losing effectiveness and isn't safe for use.

Dog or cat owners traveling with their diabetic furry friend must carry Prozinc vials in travel coolers, like the ones from 4AllFamily.

 4AllFamily Travel Coolers and Cooling Cases for Insulin

What is Prozinc's shelf life?

According to the manufacturer, “Prozinc carries a two-year shelf life from the date of manufacture.” The expiration date is labeled both on the vial container and the carton box. Always check it before use. Past the expiration date, Prozinc starts losing efficiency. 

Injecting your dog or cat with expired insulin can lead to severe consequences, including prolonged high blood glucose, severe hyperglycemia, coma, and death in the worth cases.

How long is prozinc good for after opening?

Irrespective of its labeled expiration date, Prozinc veterinary insulin is safe for use within 60 days after opening. 

We recommend dog and cat owners write down the vial's opening date to avoid confusion.

Why is my dog’s Prozinc insulin cloudy?

Unlike Vetsulin, Prozinc is an aqueous suspension (a heterogeneous mixture of insulin and protamine that delays its absorption).

Once mixed, suspension insulins have a white, cloudy appearance, so it’s normal that Prozinc is cloudy. However, any clumps or persistent white particles may indicate the insulin has gone bad. In that case, discard it and get a new vial from the refrigerator.

Related article: Can you prefill insulin syringes, and how long are they good for?

How to Store and Refrigerate Caninsulin? 

Caninsulin is an intermediate-acting veterinary insulin (8-10 hours duration) prescribed for diabetes management in dogs and cats. It's an aqueous suspension made from purified porcine insulin.

Caninsulin is available both in vials compatible with U-40 syringes and auto-injectable pens (VetPen).

Whatever the format, it must be kept refrigerated. So, if your four-legged companion has been prescribed Caninsulin, you must take extra precautions as to the storage of its life-saving medicine.

According to MSD Animal Health, Caninsulin should be protected from light and high temperatures. Therefore, prior to first use and in between doses, it must be refrigerated between 36°F and 46°F (2°C and 8°C).

The manufacturer does not say how long Caninsulin can be left out of the fridge without deteriorating. Instead, it invites dog and cat owners to contact their veterinarian if they’ve accidentally left a vial or pen of Caninsulin out of the fridge and ask for instructions.

Trusted sources & References

[1] Thompson A, Lathan P, Fleeman L. Update on insulin treatment for dogs and cats: insulin dosing pens and more. Vet Med (Auckl). 2015 Apr 15;6:129-142. doi: 10.2147/VMRR.S39984. PMID: 30101100; PMCID: PMC6067590.

December 01, 2022


4AllFamily Customer Care Team said:

Thank you Phyllis!

Phyllis Polen said:

Hello owner, Your posts are always well-formatted and easy to read.

4AllFamily Customer Care Team said:

Hi Luz,
Thanks for your comment! We’re glad you like it and hope you’ve found the information you were looking for,
4AllFamily Customer Care Team

Luz Downs said:

To the admin, Thanks for the great post!

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The information presented in this article and its comment section is for informational purposes only and is not intended as a replacement for professional medical advice. Always consult with a qualified healthcare provider for any medical concerns or questions you may have.