If your insulin froze by mistake, do not use it, even after it thaws and looks normal. Every US insulin label we read (18 of them) says not to use insulin that has been frozen. Set it aside, check your backup, and get a replacement before your next dose is due.
The CDC puts it plainly: "Insulin that has been frozen can break down and will be less effective." And looking at it will not settle the question. In a 2009 federal court order over a frozen insulin shipment, Lilly's expert is described as saying that insulin exposed to sub-freezing temperatures "may undergo subtle changes that are not detectable by physical inspection."
This article provides general information about medication management and is not a substitute for professional medical advice. Consult your doctor or pharmacist for advice specific to your medications.
Is Frozen Insulin Okay to Use After It Thaws?
No. Lantus says "Do not use LANTUS if it has been frozen." Humalog and NovoLog say the same.
The worry is that it may not lower your blood sugar the way your dose expects. Missing insulin shots is one of the two most common causes of diabetic ketoacidosis (DKA), according to the CDC.
And do not try to rescue it in the microwave. In a 1994 case report, a patient's diabetes control got markedly worse after he did.
How Can You Tell If Insulin Has Been Frozen?
Sometimes it is obvious: ice inside, a pen that feels solid, or a frosted look. Novo Nordisk lists "clumping, frosting, or precipitation" as freezing damage in its temperature Q&A.
Often it is not, and what you can check depends on your insulin.
- Clear insulin (rapid-acting, regular and long-acting kinds). The label says it should look clear and colorless. A thawed pen can still look that way, which is why the court record above matters. If you know or suspect it froze, treat it as frozen.
- Cloudy insulin (NPH, 70/30 and other premixed kinds). The Humulin N label says it "should look white and cloudy after mixing. Do not use it if it looks clear or contains any lumps or particles." Lumps after a cold night are a clear stop sign.
What if your fridge thermometer read 33°F but nothing turned to ice? Novo Nordisk's Q&A says its products "should not be frozen (below 36 °F or 2 °C)" and "Do not use products exposed to frozen temperatures." That line covers Novo Nordisk products. For other brands, ask your pharmacist or call the maker (numbers below).
What Lantus, Humalog, NovoLog and Other Insulin Labels Say About Freezing
We read the full FDA labels on DailyMed for 18 US insulins. Every one says not to use it once it has been frozen. Toujeo's version: "Throw away your pen if it has been frozen." Here is what else each label says.
| Insulin | Should look | What else its label says |
|---|---|---|
| Humalog | Clear | Do not use it if you see "lumps or particles in it." |
| NovoLog | Clear | Do not use it "if it is thick, cloudy, or is colored." |
| Fiasp | Clear | Keep unused vials in the fridge "but not in or near a freezing compartment." |
| Lyumjev, Admelog | Clear | Admelog: "If a vial has been frozen or overheated, throw it away." |
| Humulin R, Novolin R | Clear | Novolin R: if it is cloudy or has particles, "do not use it and call Novo Nordisk." |
| Lantus, Basaglar, Semglee | Clear | If it is cloudy or slightly colored, "return it to your pharmacy for a replacement." |
| Toujeo | Clear | The pen "should not be stored in the freezer and should not be allowed to freeze." |
| Tresiba | Clear | "Do not store in the freezer or directly adjacent to the refrigerator cooling element." |
| Humulin N, Novolin N | Cloudy after mixing | Humulin N: do not use it "if it looks clear or contains any lumps or particles." |
| Humulin 70/30, Novolin 70/30, Humalog Mix75/25, NovoLog Mix 70/30 | Cloudy after mixing | NovoLog Mix: do not use it "if it looks clear or if it contains solid particles." |
Frozen Insulin: What to Do Next
- Set it aside and do not inject it. Keep the box until the replacement is sorted. It shows the lot number and expiration date.
- Check your backup. An in-use pen or vial kept out of the fridge may still be usable within the room-temperature days its own label allows. Those limits differ a lot: a Humalog Mix75/25 KwikPen gets 10 days, while a Tresiba pen gets 56 days. If the backup sat in the same fridge, check it too.
- If you already injected from it, check your blood sugar more often than usual and tell your prescriber if it runs high.
- Call your pharmacy for a replacement fill today. The next section covers who pays.
- If your next dose is due before you can get more, call your prescriber's after-hours line. Do not switch to a different insulin on your own. The FDA says to "always switch insulin under a doctor's care, with close monitoring of your blood sugar." If you can't reach anyone and have no other insulin, go to urgent care or the ER instead of skipping doses. For DKA, the CDC says to "go to the emergency room or call 911 right away" if your breath smells fruity, you can't keep food or drinks down because of vomiting, you're having trouble breathing, your blood sugar stays at 300 mg/dL or above, or you have multiple signs of DKA. It says the same for high ketones. Early signs include being very thirsty and urinating a lot. Our sick-day insulin guide explains ketone checks.
Will insurance replace frozen insulin?
It depends on your plan. Plans limit how early you can refill, so a replacement fill may be rejected as "refill too soon." Your pharmacist can call the plan's help desk and ask for an override for damaged medication. Here is how the rules differ:
- One plan's written policy, as an example: HAP CareSource's Michigan Marketplace policy allows "a single refill-too-soon override per medication (including strength) per rolling twelve (12) months" for damaged medication. If the damage happened "in the process of shipment to the member," the pharmacy is responsible for replacing it.
- A large benefit manager words it differently. Express Scripts says that, depending on your plan, you may get an early refill if medication was "lost or damaged due to an emergency or disaster event."
- In a federally declared emergency, CMS expects Medicare drug plans to remove "refill too soon edits" for people in the affected area.
If you have Medicare, each covered insulin costs "no more than $35" for a one-month supply, though "other costs may apply," per Medicare.gov. Our guide on how early you can refill a prescription has a script for the pharmacy counter.
Questions about whether your insulin is still good can go to the maker. The FDA lists these lines: Lilly 1-800-545-5979, Novo Nordisk 1-800-727-6500, Sanofi 1-800-633-1610, Biocon Biologics 1-833-986-1468. The FDA notes the numbers can change.
No refills left, and can't reach your prescriber? State rules on emergency refills vary widely, a 2021 review of every state's pharmacy laws found. Ask the pharmacist what your state allows. Then work through what to do when you run out before a refill. Away from home? See how to get a same-day refill while traveling and the vacation override.
Can Insulin Freeze in the Fridge?
Yes. In a 2019 study of insulin users' fridges, 57 of 230 sensors placed next to the insulin logged below-freezing temperatures at some point. (Three of the five authors worked for the company that made the sensors.)
Where it sits matters. The Tresiba label says not to store it "directly adjacent to the refrigerator cooling element," and the Fiasp label says "not in or near a freezing compartment." A Sri Lanka Medical Association guideline, quoted in a 2021 review, suggests the "middle compartment of a refrigerator."
Hotel fridges do it too. In a 2021 survey, people who suspected cold had ruined their insulin wrote things like "Hotel fridge too cold" and "It was frozen by a B&B fridge." The 2021 review describes a DKA case traced to "an insulin vial that had frozen in a hotel refrigerator."
A cheap fridge thermometer next to your insulin will tell you what the dial won't.
Will insulin freeze in a cooler or a cold car?
It can. The FDA says, "If you are using ice, avoid freezing the insulin." The 2021 review adds that pens and vials "should never be kept directly on ice."
Cars can freeze insulin too. One person in the survey wrote: "Forgot the insulin in the car in the winter, frozen solid." The American Diabetes Association's advice, quoted in a 2023 Cochrane review, is direct: "Never store insulin in the freezer, in direct sunlight, or in the glove compartment of a car." If your insulin baked in a hot car instead, see our hot car guide.
What About a Frozen Ozempic, Wegovy, Mounjaro or Zepbound Pen?
These pens are not insulin, but the Wegovy and Zepbound labels also say not to use a pen that has been frozen. See our Ozempic out-of-the-fridge guide and our Mounjaro fridge guide, which also covers Zepbound.
How Pillo Helps
A frozen pen hurts most when it was your last one. Pillo's stock tracking and refill reminders tell you before you run low, so a spare is on hand. With dose notes, you can add a note to the first dose from a replacement pen. If your readings change, that note shows when the switch happened, so you can tell your prescriber.
Managing a parent's insulin? Dependents tracks their schedule in your own app, free for up to 2 dependents. Lost track of a shot? Read what to do when you can't remember if you took your insulin.
FAQ
Can you use insulin that froze and then thawed?
No. Every US insulin label we read says not to use insulin that has been frozen, and the CDC says frozen insulin "can break down and will be less effective." Thawed insulin can look normal, so looks are not a safe test.
Is insulin still good if it got cold but didn't freeze?
All 18 insulin labels we read give a fridge range of 36°F to 46°F. Novo Nordisk says its products "should not be frozen (below 36 °F or 2 °C)." For other brands, call the maker's line or ask your pharmacist about your pen.
What if the frozen insulin is the only insulin I have?
Do not inject it. The FDA says, "Do not use insulin that has been frozen." Call your pharmacy and your prescriber's after-hours line for a replacement or an emergency fill. If you can't get insulin before your next dose, go to urgent care or the ER instead of going without. Missing insulin shots is a common cause of DKA.
Will my pharmacy replace insulin that arrived frozen?
Call the pharmacy the day it arrives. Under at least one plan's written policy, damage "in the process of shipment" is the pharmacy's to replace. Other plans may treat it as a damaged-medication override instead. Keep the box and packing slip.
What if my pet's insulin froze?
The Vetsulin and ProZinc labels both say "Do not freeze." Call your vet before the next shot. Our guide to a cat's missed insulin dose explains why guessing is risky with pet insulin.
This article is for informational purposes only and does not constitute medical advice.
