If you're one of the over 7 million Americans relying on insulin to manage diabetes, you know how vital this medication is. Yet, like many, you may worry about your insulin going bad, which can not only impact your health but also hit your wallet hard. Fortunately, understanding a few key points can help prevent such mishaps. 

In this article, we'll explore how insulin can go bad and the signs and symptoms you need to look out for. More precisely, we'll answer the following questions: 

  • What can make insulin go bad?
  • What are the symptoms and risks of using bad insulin?
  • How to tell if your insulin is bad?
  • How to prevent your insulin from going bad?
4AllFamily Insulin Coolers

Related article: Does Insulin Need to Be Refrigerated? Essential Storage Tips!

Can Insulin Go bad?

Yes, insulin can go bad if not stored or handled properly. Actually, insulin often goes bad. It's a hormone that's extremely sensitive to environmental conditions, especially temperature and light.

Adhering to strict storage temperatures is very important to prevent your insulin from going bad and optimize its stability. Here's a reminder:

  • Unopened insulin should be kept refrigerated between 36°F and 46°F (2°C and 8°C) before use.
  • Once opened, insulin can be stored at room temperature, optimally between 56°F (13°C) and 80°F (26°C), for about a month.

Failure to follow these temperature guidelines can cause insulin to spoil quicker. While some insulin types have a longer shelf life than others when stored outside the refrigerator (ranging from 14 to 56 days depending on the brand and type), all insulins can go bad, including common brands like NovoLog, Lantus, Humulin, Humalog, NovoRapid, FIASP, Novolin, Levemir (discontinued in 2024), Apidra, Tresiba, Basaglar, Toujeo, and others.

But temperature isn't the only factor that can make your insulin go bad or expire faster than it should. Light exposure, bacterial contamination, and the natural expiration process are to be considered too.

Insulin can go bad if not refrigerated

As you probably know, insulin must be refrigerated to maintain its stability and potency. When stored correctly in the refrigerator at temperatures between 36°F and 46°F (2°C and 8°C), your insulin pens or vials are good until their labeled expiration date (usually about a year after the purchase date).

However, if you do not refrigerate your insulin, it can rapidly lose its effectiveness and go bad before its official expiration date. This is particularly true if insulin is kept at room temperature for longer than the generally recommended period of about one month, although the exact duration can vary based on the specific type of insulin.

Insulin can go bad if exposed to heat

Heat exposure is a critical threat to insulin, and probably what most often makes it go bad. When exposed to high temperatures for even a brief moment, your insulin will spoil much quicker than it should.

For instance, your insulin can quickly go bad if left in a car. Cars can heat up quickly when parked in the sun, reaching temperatures far beyond the safe storage threshold for insulin. For instance, on an 85°F (29°C) day, the temperature inside a car can soar to 120°F (49°C) within 30 minutes, which can quickly spoil any insulin left inside. 

Placing your insulin pen or vial near a stove, oven, or other heat-generating appliances can also expose it to temperatures that exceed safe limits. Even a brief exposure during cooking can heat insulin to levels that may quickly compromise its integrity.

Carrying your insulin pen in a pocket without a cooling case during a hot summer day can also subject it to temperatures high enough to cause damage. To prevent your insulin from going bad in such conditions, always carry it in insulated cooler cases.

Insulin expires!

Like many medications, insulin comes with an expiration date, which indicates until when the manufacturer can guarantee its safety and effectiveness. Using insulin beyond this date can lead to decreased efficacy and potential health risks.

Related article: How Long is Insulin Good for & When Does it Expire?

Freezing can also ruin your insulin

Watch out for cold temperatures as well! Insulin should never be frozen. It's a protein dissolved in water, and just like water, its freezing point is at 32°F (0°C). Freezing temperatures can irreversibly alter the molecular structure of insulin, causing it to go bad and lose its potency, even if it thaws afterwards. To maintain a safety margin, you should always make sure your insulin is kept above 36°F (2°C).

Light can damage your insulin too 

Exposure to light can lead to photodegradation of insulin, which can seriously and irreversibly affect its therapeutic properties. To protect insulin from light, always store it in its original container with the opaque cap on (for insulin pens), and avoid leaving it in direct sunlight.

Insulin contamination 

Biological contamination of insulin is unlikely, yet it remains a possibility. Improper handling of your vials or pens can lead to your insulin going bad because of bacterial contamination.

To mitigate this risk, always use a new sterile needle or syringe to inject insulin. Remove the needle from your injectable pen immediately after use to prevent air and bacteria from entering the device and contaminating the insulin. Furthermore, you should never share an insulin pen with another person, even if the needles are changed, as this increases the risk of contamination.

Related article: How to Travel With Insulin That Needs Refrigeration or Cooling!

Do bad batches of insulin happen? 

Although rare due to stringent manufacturing and quality control standards, bad batches of insulin can happen. Issues like breaches in the cold chain during shipping or handling might lead to insulin going bad. For instance, Novo Nordisk had to recall bad batches of insulin cartridge holders in 2017. So, if you have doubts about a bad batch of insulin, it's always a good idea to bring it to your pharmacist and ask for advice. 

Related article: A Step-by-Step Guide to Using Insulin Pens for Injection.

Bad Insulin: Symptoms, Risks, and Side Effects

Now, the real question is: what happens if you take bad insulin? Using insulin that has gone bad, degraded, or has lost efficiency can pose significant risks for your health. The primary risk of injecting bad insulin is the inability to properly manage blood glucose levels, which can lead to serious diabetes-related complications.

High blood sugars 

Unexplained high blood sugar levels are a primary symptom that your insulin may have gone bad. When insulin loses its potency, it's akin to injecting water-it simply doesn't help lower glucose levels. 

So, if you observe that your blood sugars remain unusually high even after injecting insulin, you should check the condition of your insulin. Switching to a fresh pen or vial from your refrigerator for your next dose can help determine if the previous batch was compromised.

If your blood sugar levels do not return to normal, seek medical advice immediately.

Prolonged high blood sugar is dangerous and can potentially lead to diabetic ketoacidosis, a serious diabetes complication.

Related article: How Long Can a Diabetic go Without Insulin?

Other side effects of bad insulin

Using bad insulin can also lead to complications due to fluctuating blood sugar levels between high and low. This unpredictability arises because bad insulin may still function, but its effectiveness can vary greatly. At times, it might lower blood glucose levels somewhat, while at other times, it may have no effect at all. This inconsistency makes it extremely challenging to maintain stable blood sugar levels, and not only hampers effective diabetes management but also increases the risk of both short-term and long-term complications.

Additionally, injecting bad insulin could also lead to increased skin reactions at the injection site, such as redness, swelling, irritation, or pain. This might be due to the breakdown products in the insulin formulation that irritate the skin or tissue.

If you experience any symptoms of using bad insulin, check the insulin's appearance and efficacy and consult with your doctor if you have doubts. Immediate action can help prevent the more severe side effects and ensure uninterrupted diabetes management. 

Related article: 10 Tips That Work to Inject Insulin Without Pain!

Can bad insulin make you sick?

While using bad insulin itself may not be inherently harmful if it's merely ineffective, the consequences of not adequately managing blood glucose can be severe. In other words, it won't make you sick directly, but the resulting high blood sugar levels can when prolonged. 

Persistent high blood sugar (hyperglycaemia) caused by bad or ineffective insulin can lead to prolonged hyperglycaemia and various health complications, including diabetic ketoacidosis, neuropathy, cardiovascular diseases, and others. Diabetic ketoacidosis symptoms include nausea and vomiting, abdominal pain, confusion or altered mental state, rapid breathing, fruity-scented breath, and others. It requires immediate medical attention as it can lead to coma or even death if untreated.

If your insulin is bad because it has been contaminated-through exposure to bacteria or improper handling-then, the risks extend beyond diabetes management. Injecting contaminated insulin can introduce bacteria directly into your bloodstream or tissue, leading to serious infections. While incidents of contamination with insulin are very rare due to the sterile manufacturing and packaging processes, they can still occur and pose serious health risks. 

How To Tell If Insulin Is Bad?

You suspect your insulin has gone bad? You feel like something isn't right. You can sometimes tell if your insulin bad simply by visually inspecting it. But not always, so if you have doubts and experience unusually high blood sugars, make sure to switch with a new pen or vial from the refrigerator and ask your doctor for advice!

Visible signs of bad insulin

Most insulins are meant to be clear and colorless. Any changes in appearance can be a strong indicator of an issue:

  • Color change. Insulin that has turned yellowish or has taken on any unusual coloration has probably gone bad.
  • Cloudiness or particles. Clear insulin that appears cloudy, or has visible particles, strings, or clumps, is likely compromised. Immediately dispose of this insulin.
  • Frost or crystallization. Any signs of frost or crystals within the vial or pen suggest that the insulin has been frozen at some point, which can irreversibly affect its effectiveness.

Is cloudy insulin necessarily bad?

No, cloudy insulin isn't always bad, as some insulin types and naturally cloudy! Insulins like Novolin N, Humulin N, and Insulatard are examples of NPH (Neutral Protamine Hagedorn) insulin, which is intentionally cloudy due to its specific formulation. However, even for cloudy insulins, any separation, such as clumps settling at the bottom or a frosted interior of the vial or pen, can indicate that the insulin has degraded. Do not use it!

Related article: Clear vs. Cloudy Insulin, Why it Matters! 

Key Takeaways on Identifying Bad Insulin: Always perform a visual check before using your insulin. If the insulin does not look as expected or if it shows any of the warning signs mentioned above, do not use it. In case of any doubt regarding insulin integrity, the safest approach is to dispose of the questionable insulin and use a new, unopened vial or pen until you get professional advice from your doctor or pharmacist

How To Prevent Your Insulin From Going Bad?

Fortunately, there are countless measures you can take to prevent your insulin from going bad. We're not just talking about safeguarding your health, bu also avoiding the costly loss of your vital medication. Here's what you can do to ensure your insulin remains potent and safe for use:

Store your insulin properly

Proper insulin storage is key here! Insulin pens, vials, or cartridges should be stored in a refrigerator between 36°F (2°C) and 46°F (8°C) until use. Once opened, they can be stored at room temperature, but always below 77°F (25°C) and for up to a month maximum. Additionally, remember the following to avoid common storage mistakes:

  • Avoid freezing. Store your insulin away from the freezer compartment to prevent accidental freezing.
  • Monitor opening dates. Always keep track of when you first open your insulin pen or vial to ensure it's used within the recommended duration.
  • Avoid heat exposure. Avoid exposure to high temperatures; never leave insulin in a hot car, near a stove, or a fireplace, and never microwave insulin.
  • Shield from light. Exposure to direct or intense light can degrade insulin. Store it in its original container and keep it out of direct sunlight.
  • Separate new and used insulin. Designate specific areas in your refrigerator and storage spaces for new and currently used insulin to prevent confusion and accidental use of expired insulin.
  • Check your insulin before each use. Before injecting insulin, check its appearance for any signs of crystallisation, discolouration, or unusual particles. If any abnormalities are found, discard the insulin.
  • Backup insulin storage solutions. In case of power outages, have a backup plan such as a generator or a secondary cooler to maintain the insulin at the required temperature until power is restored.
  • Educate household members. Ensure that all household members understand the importance of proper insulin storage and know how to handle your insulin correctly!

Related article: How to keep insulin cool during a power outage and without electricity?

Use an insulin cooler

If you're living in or traveling to places where the ambient temperature gets above 77°F (25°C), you need to keep your in-use insulin pen or vial cool and protected from the heat. Consider these options:

  • DIY insulated cooler bag. An insulated lunch bag with ice packs can be a temporary solution, but it's not recommend long-term, as temperature may fluctuate a lot inside and the set-up isn't reliable enough for insulin.
  • Medical-grade insulin coolers. Invest in a specialized insulin cooler for more reliable temperature control. Products from 4AllFamily are designed to carry your insulin at the perfect temperature-range, whether you need to transport refrigerated insulin or room-temperature insulin. Besides, they're TSA-approved for air travel, so you can even take your insulin on a plane!


4AllFamily Insulin Coolers


Use insulin vial protector

For those using insulin vials, minimize the risks of contamination by using an insulin vial protector with sanitary cap. These protective sleeves not only keep the vial's surface clean but also prevent breakage in case of a drop.

4AllFamily Insulin Vial Protector


We'd Love to Hear From You!

Your experiences are invaluable to us and can help others facing similar challenges. Have you ever found your insulin to be bad? Don't hesitate to share your questions and stories in the comments below!

Article Last Updated on May 22, 2024

September 18, 2021


Mike said:

Hello Steve Ancell,
Hope you are well!
Well, in fact, it depends and those instructions do not seem accurate! I am not sure what the conversation was exactly, but unopened insulin must be kept between 36-46F / 2-8C all the time and can resist until the expiration date. If you open it or it breaks this cold chain, then it can be stored between 36-79F usually for up to 28 days. It depends on the insulin or medicine because there are some that resist for up to 28-31 days and others for up to 14 days. You should read the medicine label itself from the manufacturer as it is always mentioned there…
Other than that, you can not feel the temperature of the medicine by touch, therefore you should always use devices that are made to store medicines correctly to be sure at what temperature you are storing them all the time.
Usually, unopened insulin is stored in the fridge by the majority of people. However, there are some recent studies that show that the fridge doors are opened on average 15-20 times a day and it may fluctuate the temperature of the fridge inside and therefore it would decrease the efficiency of insulin itself. If the temperature chain breaks for some minutes the efficiency decreases and it leads to more dosages needing to be used afterward to have the results you could have with fewer dosages if insulin was stored properly. This usually is seen more during summer!
I am not 100% sure about the real effect that storing insulin in fridges has on the efficiency of insulin, but we should wait until these studies are more accurate I believe.
Hope all this information helps and if you have any more questions, we would be happy to help you.
Best regards,

Steve Ancell said:

I was told if the bottle of insulin was warm to the touch, it was bad.
Instruction came from the VA.

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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.