The Ultimate Guide to Storing Your Dog’s & Cat’s Insulin: Keep It Safe, Effective, and Long-Lasting

Quick Answer: To store your dog’s or cat’s insulin properly, keep it refrigerated between 36°F and 46°F (2°C - 8°C) and avoid freezing. Once opened, most insulins last 42-60 days at room temperature but must be protected from heat. Always check for changes in appearance and discard expired or spoiled insulin.

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.

Why must Veterinary Insulin be Refrigerated?

Insulin is a life-saving medication for diabetic dogs and cats, but it requires strict storage conditions to remain effective. Unlike many other medications, insulin is a biological drug made from living cells, which makes it highly sensitive to temperature changes, light exposure, and contamination. If insulin is not stored properly, it can lose its potency, leading to poor blood sugar control and serious health complications for your pet.

To ensure the insulin you administer remains safe and effective, it is essential to store it correctly and follow the manufacturer’s guidelines. Here are the key reasons why refrigeration is crucial:

Why Veterinary Insulin Needs Refrigeration:

• 🧬 Made from Living Sources – Insulin is a biological product, meaning its molecular structure can break down easily if exposed to improper conditions.
• 🌡️ Temperature Sensitivity – Heat or freezing temperatures can damage insulin, making it ineffective and potentially dangerous for your pet.
• ⚠️ Spoilage Risks – If not properly refrigerated, insulin can spoil, become contaminated, or degrade, leading to erratic blood sugar levels in your pet.
• 📋 Different Insulin Types, Different Needs – Brands like Vetsulin, Prozinc, and Caninsulin each have specific storage requirements, so always check the manufacturer’s guidelines.

By keeping your pet’s insulin refrigerated at the recommended temperature (36°F - 46°F / 2°C - 8°C), you help preserve its effectiveness and ensure your furry friend receives the best possible diabetes management.

Related article: Insulin Storage: 10 Common Mistakes to Avoid When Storing Your Insulin Pens and Vials

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’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?

Ensuring your pet's insulin is safe and effective is crucial for proper diabetes management. Vetsulin, like all insulins, can degrade over time or when exposed to improper storage conditions. Using spoiled insulin can lead to poor blood sugar control, putting your pet at risk of serious health complications.

Before administering Vetsulin, always inspect it carefully to check for signs of spoilage. Here’s how to tell if your dog’s or cat’s insulin has gone bad:

Visual Signs of Spoiled Vetsulin:

• 🎨 Color Change – Fresh Vetsulin should be clear and colorless. If you notice a yellowish, brownish, or unusual tint, the insulin may have degraded and should be discarded.
• ☁️ Cloudiness or Clumps – Vetsulin should be a smooth liquid with no floating particles. If you see clumps, white particles, or persistent cloudiness, it may be contaminated or broken down.
• 🧵 Strings or Frost Inside the Vial – Look closely for unusual string-like formations or frosty crystals inside the vial. These are signs that the insulin has been exposed to freezing temperatures and is no longer effective.

If you notice any of these warning signs, DO NOT use the insulin. Discard the vial and use a fresh one from the fridge.

🚨 Additional Warning Signs

Even if the insulin looks fine, it may still be ineffective. Pay attention to your pet’s behavior and health:

• Increased thirst and excessive urination
• Unexplained weight loss
• Lethargy or low energy levels
• Signs of high blood sugar (hyperglycemia), such as confusion, vomiting, or loss of appetite

If you suspect bad insulin is causing these symptoms, consult your veterinarian immediately and replace the vial. Ensuring Vetsulin is properly stored and checked before each use can prevent dangerous blood sugar fluctuations and keep your pet healthy.

Related article: How to Store Insulin Without Refrigeration?

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.

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.

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 Use Insulin That’s Been Left Out for 1 Hour or Overnight?

How to Store and Refrigerate Caninsulin? 

Caninsulin is an intermediate-acting veterinary insulin that plays a crucial role in managing diabetes in dogs and cats. Since insulin is a biological drug, it is highly sensitive to temperature changes, light exposure, and improper handling. To maintain its potency and ensure it remains safe for your pet, Caninsulin must be stored correctly at all times.

Improper storage can reduce insulin’s effectiveness, leading to poor glucose control and potential health risks for your pet. To avoid this, follow these essential Caninsulin storage guidelines:

Caninsulin Storage Checklist:

• 🧊 Keep Refrigerated at 36°F - 46°F (2°C - 8°C) – According to MSD Animal Health you should store Caninsulin in the fridge before first use and between doses. Avoid placing it in the fridge door, as temperature fluctuations can affect its stability.
• ❄️ Never Freeze Insulin – If Caninsulin is exposed to freezing temperatures, it becomes unusable and must be discarded immediately.
• ☀️ Protect from Direct Light and Heat – Store Caninsulin in its original packaging to prevent light exposure, and keep it away from heat sources such as stoves, direct sunlight, or warm storage areas.
• 📅 Track Expiration and Usage Timeline – An unopened vial of Caninsulin remains effective until the manufacturer’s expiration date. Once opened, it should be used within 42 days and then discarded.
• 🚗 Use an Insulin Cooler for Travel – If you need to travel with Caninsulin, use a medical-grade insulin travel cooler to maintain the proper temperature and prevent degradation.
• ⚠️ Contact Your Vet If Left Out of the Fridge – If you accidentally leave Caninsulin at room temperature for an extended period, consult your veterinarian before using it. Insulin exposed to high temperatures may lose potency, which could lead to unstable blood sugar levels in your pet.

Proper insulin storage is essential to ensure safe and effective diabetes management for your dog or cat. Always handle Caninsulin with care, and when in doubt, replace any questionable insulin to avoid potential health risks.

📌 Key Takeaways on Storing Your Dog’s & Cat’s Insulin:

• 🧊 Always Refrigerate Insulin – Veterinary insulin like Vetsulin, Prozinc, and Caninsulin must be stored at 36°F - 46°F (2°C - 8°C) to maintain effectiveness. Never freeze insulin, as it will become unusable.
• ⏳ Follow Usage Guidelines – Once opened, Vetsulin and Caninsulin last 42 days, while Prozinc is good for 60 days. After this period, insulin must be discarded, even if it looks fine.
• ⚠️ Check for Spoiled Insulin – Color changes, cloudiness, clumps, or floating particles indicate that insulin has gone bad. Using ineffective insulin can cause dangerous blood sugar fluctuations in diabetic pets.
• ☀️ Protect from Heat and Light – Avoid direct sunlight, warm storage areas, and fluctuating fridge temperatures. If traveling, use an insulin cooler to keep your pet’s medication safe.
• 🐶 Consult Your Vet If in Doubt – If insulin is left out of the fridge for too long or shows signs of spoilage, always check with your veterinarian before use to prevent health risks.

💬 We’d Love to Hear From You!

Do you have insulin storage tips or questions about keeping it safe? Have you ever dealt with spoiled insulin? Share your thoughts in the comments! Your experience could help other pet owners keep their furry friends healthy. Let’s support each other!

📆 Article Update History:

✅ Updated: March 9, 2025 

Originally Published: December 1, 2022

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. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6067590/