Can You Freeze Insulin and What Really Happens if you Do?

Lots have been written about insulin and heat. Still, little information is available as to what happens to insulin when it freezes? Insulin should never be exposed to extreme temperatures, whether hot or cold. Just like warm insulin loses efficiency, insulin that has frozen is not safe for use anymore. Your injectables have to be stored cold. But how cold can insulin get? Can you still use insulin vials or pens that have frozen? What would the consequences be? Let's answer all of your questions here!

Table of Content: 

Can you freeze insulin?

Is frozen insulin still good?

How to tell if your insulin has frozen?

How to prevent insulin from freezing?

Can you freeze insulin?

If the question has been left unanswered for quite a long time, there's no more doubt: you can't freeze insulin. Doctors, drug manufacturers, pharmacists, diabetes patients, biologists… everybody agrees that frozen insulin is good for trash.

What happens if insulin freezes?

Freezing breaks down insulin. Amin Zayani is an engineer living with Type 1 diabetes. He has led successful projects to protect temperature-sensitive medications. He calls the refrigerators "insulin frenemy," saying "cold is really the one overlooked problem" with insulin. In this video, he explains very well what happens to insulin if it freezes.

When frozen, the solution becomes crystals. These crystals break the molecule. As a result, insulin loses its properties, capacities, and efficiency. It won't be lowering your blood sugars anymore- or not as much as it should.

So, how cold can insulin get?

The temperature-sensitive hormone must be protected from extreme temperatures. When stored, your stocks of insulin must be refrigerated between 36–46°F (2–8°C). Once open, your pens, cartridges, and vials can stay at room temperature for about a month but should not be exposed to temperatures over 77°F (25°C).

Insulin is a protein dissolved in water. Insulin freezing point is at 32°F (0°C), just like water. To maintain a safety margin, you should always keep your insulin above 36°F (2°C). In any case, insulin should never be stored under 32°F (0°C).

During winter keep insulin close to body warmth

Is frozen insulin still good?

No. Frozen insulin does not work anymore. Injecting frozen insulin, even if it has thawed, can seriously affect your diabetes management. Let's see what the drug manufacturers themselves say about it.

Can you use frozen insulin?

Apart from the fact that you would technically not be able to inject frozen insulin, it's absolutely recommended you do not. I've been investigating a bit more and checked what the leading manufacturers say about frozen insulin. It's pretty straightforward. All agree you should not use insulin that has been frozen.


"Unused NovoLog® should be stored in a refrigerator between 2° and 8°C (36° to 46°F). Do not store in the freezer or directly adjacent to the refrigerator cooling element. Do not freeze NovoLog® and do not use NovoLog® if it has been frozen"


"Do not allow Lantus to freeze. Do not put Lantus in a freezer or next to a freezer pack. If you see frost or ice crystals in your Lantus solution, throw it away."


"Storing the Humulin R U-500 vial: Do not use if it has been frozen."

You should verify specific rules for the insulin you're using. Apidra, Humalog, Novorapid, Tresiba, Levemir, Toujeo, etc, all firmly recommend not to use insulin that has frozen, even if it has thawed afterward.

What about thawed insulin?

What if your insulin has frozen but is now back to its liquid state? You shouldn't use it either. The mere fact that it has frozen, even briefly, makes your insulin good for nothing else but the garbage.

The freezing process has already broken down your insulin, and you would inject yourself a hormone that's not working. Your blood sugar levels won't lower. Worst, they'll get uncontrollable!

Westminster Medical School published an interesting case study. A 28 years old man thawed his accidentally frozen insulin with his microwave defrost mode. He subsequently ended up in emergency care due to a total loss of blood sugar control.

How to tell if your insulin has been frozen?

If you suspect your insulin might have frozen, you should carefully scrutinize it. Some signs clearly indicate that your insulin is not good anymore.

What does frozen insulin look like?

It looks frozen! Insulin freezes like water do. It becomes solid and opaquer. When your insulin is frozen, you technically can't inject it. It would not pass through the needle.

It's more complicated to tell if your insulin has frozen and then thawed. After it melts, your insulin gets back to its liquid state. Look for changes in color and texture. Bad insulin looks cloudy. It's often clumpy, and you can see little white strings and particles.

Unusually high glucose levels can also be a sign that there's something wrong with your insulin.

Frozen insulin looks cloudy

What to do if your insulin has frozen?

Insulin that has frozen is not safe to use. Do not try to thaw it. The side effects of using insulin that has frozen can be severe. You should immediately throw your insulin away and get a new vial or pen.

How to prevent your insulin from freezing?

Situations where your insulin might accidentally freeze are much more common than you'd think: a power outage leaves you without heating; you've forgotten your insulin in your car overnight; you live or travel in icy places; you've put your insulin in direct contact with your medicine cooler's ice packs. There are dozens of situations where it could happen. Here's how you can protect your insulin from freezing and save $$$ worth of medications.

Store your insulin in the right fridge compartments

Domestic fridges do not follow the same standards as medical fridges. The temperature is not the same everywhere in your fridge, and it actually varies quite a lot. The fridge zones that are closer to the freezer compartments are at risk of freezing temperatures. The vegetable, meat, and fish bottom drawers are often the coldest zones too. The ideal place to keep your insulin safe from freezing is your fridge's middle shelf. It's the one that risks no freezing and has the most stable temperature.

Of course, never keep your insulin in the freezer. In case of a power outage, we do recommend storing your insulin in the freezer, but it's only in case it's out of power!

Store insulin on the fridge middle shelf

In cold weather, keep your insulin close to your body

Suppose you're traveling to or living in a cold-weather destination. The best way to prevent your insulin from freezing is to keep it close to your body. Your body warmth should be enough to keep it safe. Place your insulin pens or vials in your inside pockets or even in direct contact with your skin.

The same applies if you're wearing an insulin pump. The insulin in the tubings and reservoir could freeze if the ambient temperature is cold. Some insulin pumps like the Tandem T:Slim are equipped with temperature sensors that warn you when the pump gets too cold.

In warm weather, choose an insulin cooler with anti-freeze security

Insulin also has to be protected from the heat and should never be exposed to temperatures over 77°F (25°C). Whenever the ambient temperature is higher than that, you should equip yourself with an insulin cooler. The problem is that poorly constructed insulin coolers might freeze your insulin!

Fortunately, some portable medicine fridges come with anti-freeze security. For example, 4AllFamily's cooling cup works with Biogel crystals packs. These crystals freeze at 2°C / 35.6°F, while insulin freezes at 0°C / 32°F. It does prevent your insulin from freezing, even if it's in direct contact with the frozen pack. 

4AllFamily Insulin Cooler


Share your bits of advice and experiences too! Have you ever had to deal with frozen insulin? What did you do?

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