Safe and effective use of insulin requires proper storage

Elena Toschi, MD


Insulin is a naturally occurring, glucose-lowering hormone used by many people with diabetes to control their blood sugar. In people with type 1 diabetes, supplemental insulin makes up for the insulin that is not produced by the body. People with type 2 diabetes may need to take insulin if they cannot maintain adequate blood sugar control with other medications.

Insulin is manufactured to be identical to the insulin produced by the human pancreas. These synthetic insulins can work from a few hours (rapid-acting insulin) to a whole day (long-acting insulin). They are typically injected via a needle or pen.

Guidelines for proper insulin storage

All insulins must be stored with care to ensure that they remain safe and effective. Improper storage could result in the breakdown of insulin, affecting its ability to effectively and predictably control your blood sugar level.

Depending on the type of insulin you are prescribed, there may be some subtle differences in how best to store it and how long it will last once open. Ask your doctor or diabetes educator for specifics on how to store your own insulin prescription.

Here are some general rules that reflect best practices for properly storing insulin:

  • All insulins are sensitive to temperatures that are too high or too low. Once you receive your insulin prescription, you should store all the supplies you’ve received in the refrigerator.
  • Once you open a new vial (meaning once you stick a needle in the vial) or pen, use a Sharpie to note the date you opened it right on the packaging. This will help you remember when to stop using it. Throw the insulin away 28 days after opening it.
  • Once you open a vial, keep it stored in the fridge or at room temperature. Be aware that injecting refrigerated insulin may be painful.
  • Keep an insulin pen refrigerated until you open it; after that, you can store it at room temperature.
  • Ask your doctor if your particular insulin has a shorter or longer lifespan. Some insulins must be used in as little as 10 days.
  • If you suspect your insulin was ever frozen, you should not use it. Insulin could freeze if it was left outside in extreme cold temperature, for example if it was delivered on a cold day and stayed outside for a while, or if it was left in your car. But insulin could also freeze in your refrigerator. Research presented at the European Association for the Study of Diabetes meeting in Berlin showed that domestic refrigerators may have unexpected temperature fluctuations. To ensure that your refrigerator keeps a constant temperature and does not go below the freezing point at any time, keep a thermometer in the fridge to check for a stable temperature of 39° F (or 4° C).
  • Insulin is also sensitive to hot temperatures, so do not leave it outside in extreme heat. This could happen in the summer, especially if you leave your insulin in the car for several hours, or you keep a spare insulin sample in the glove compartment of the car as backup.
  • Exposure to sunlight can also degrade insulin.
  • Always check the expiration date and do not use expired insulin.
  • Inspect your insulin before each use. Look for changes in color or clarity. Look for clumps, solid white particles, or crystals in the bottle or pen. Insulin that is clear should always be clear and never look cloudy.

Finally, if you have any doubts, start a new vial or pen to avoid unpleasant surprises.

Related Information: Living Well with Diabetes


  1. Bob

    Type 1 diabetic for 30 years. I’ve never had issues with insulin going bad until earlier this year when i used FIASP. I had it at room temp and within a week it had brown clumps. Since then i’ve started using a Frio. Insulin prices and medical costs are thru the roof. I’ve lost most any respect for medical system. Their role in society is to use their superior knowledge to help their fellow man. Its now turned into using that superior knowledge to find the sick on the ground and get every last cent from him.

  2. azure

    Safe & effective use of insulin requires being able to afford it.

    Something the US system of providing health care and the pharmacuticial industry is making more & more difficult for more people.

  3. Brian B

    I have been taking insulin for 35 years and had in both hot and cold places for extended periods with zero adverse affects.

  4. Linda

    I was diagnosed as type 2 last year, my weight was 125kg, my doctor wanted me to start insulin and encouraged a diet with an alarming amount of carbs, so I went to boots and bought a blood sugar tester that I used every day, and started on a Atkins type diet. I.e no carbs….. and when I say no carbs I really mean none. So lots of meats and fish, eggs etc. I gradually started loosing weight at a rate of 3kg per month and Im now 94kg, I have never taken insulin and in a few months I will be my target weight. my lifestyle can never go back to carbs, but I can have some nowerdays without my blood sugar increasing, so if I want a curry I can have a Nan bread with it but no rice chips etc. And to be honest when you cut out carbs you can eat a lot of really tasty things that help lose weight a fry up without the beans is fine, lamb chops and kebabs without the bread etc. The only downside is because of the extra fat intake I need to be doing daily cardio. I really believe doctors are offered too many incentives by drug companies and tend to love writing prescriptions instead of encouraging a positive change in our lifestyles.

    • Elena Toschi

      Linda: excellent job and good reminder to all of us that lifestyle modification is FIRST and should always be prescribed and renewed at every single visit (no matter what!).

  5. Mike

    Sound advice, but the big challenge with this is the insurance company restriction on refills.

    I often have vials/pens on the edge of the 28 days, but discarding means a gap in insurance coverage for refills (covered for x units per day). Expensive.

    Outlandish wish would be for some way to measure insulin effectiveness to know if it’s expiring. Currently it involves convincing the doc to prescribe a higher daily dose than I really need…

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