How long can I keep opened insulin in the fridge?

I know that opened insulin is good for at least 30 days at room temperature, but does anyone have advice on how long I can keep opened insulin in the fridge?

Reason I ask is that I have started using Insulatard in my fight against dawn phenomenon. So far so good but the thing is, I only use 1 unit a day and the pen contains 300 units. If I keep it at room temperature, I'll have to throw it out with more than 250 units still in it.

I don't have to pay for my insulin but I hate throwing it out like this. I was wondering if I could just keep the opened pen (it only comes in pen format) in the fridge so it could last longer? Also is there anything wrong with injecting cold insulin? I was told it stings?

What does the packaging say? Most online sources say 28 days, unopened, in the fridge.

Spock, I believe it says 28 days after opening. Lila I think that 28 days includes in or out of the fridge. When I'm not sure about medicines of any kind I always ask my pharmacist they have the scoop on drug information.

I have to tell you, in the end, you will need to just get over the feeling of being inefficient or costing money in your diabetes care. It is expensive, and stuff will get wasted. But if you do everything in your power to be efficient and not waste, then don't waste your worry on it.

That being said, I have even more alarming news for you, Humulin 70/30 (or Humalog 75/25) mix pens are recommended to be used within 10 days of opening.

You can keep them in the fridge, and that will slow at least some of the degradation, but insulin mix in pens lasts the shortest of all the supplied insulin forms. Some insulin formulations like Lantus and Levemir actually want you to inject at room temperature, it helps them work properly, but I don't think it matters with Humulin/Humalog mixes. If you do need insulin, you will likely start to need more as 1 unit in a basal form is almost nothing. And in the meantime, one option might to simply start using NPH overnight (it lasts 28 days in a pen).

I would be tempted to use it until it doesn't work.

Insulatard *is* NPH.

It's marketed as Novolin N in the US.

Lila, do read the packaging information on your insulin. And like Leo2 said, I'd use it until it does not work. There is nothing wrong with injecting cold insulin, I used to do it all the time when we mixed cold insulin and it was way more than one unit. When you do it does it sting?

Hi Lila. Good advice to let it go until it quits, but... when you get a high, don't think "I wonder if that was my fault". Just change it. I had that problem today, my Apidra has the habit of quitting before 28 days.


I've used Apidra for 6 weeks & longer. I keep all insulin refrigerated, or in a Frio & don't inject air into the vial. When I used Lantus, it was a goner by day 28. Levemir lasts about 7-8 weeks.

Hi Gerri. I've used both a pen and a vial for my Apidra, and continue to have the problem of it's quitting early all year long. I've speculated that neither the pens or vials are kept at the proper temperature during transportation to my pharmacy so there's nothing I can do about it.

I've also used both a pen and a vial for my Levemir; the vial will last five weeks, the pen is used up in about three weeks so no problem there.