Keeping insulin cool when traveling: wide thermos

My T1D son and wife are getting ready to spend 2 weeks on the west coast of Costa Rica, in a place where temperature frequently reaches 100F and humidity often hits 90%+. I have been experimenting with different ways to keep insulin cool with as little risk as possible. My latest experiment is the best one, and, I think, a winner. This is what I get after leaving it exposed outside in WI heat for 24 hours (yesterday was mid-80s in shade):

Here is the experiment. I used an insulated double walled stainless steel wide mouth 20 oz bottle from Klean Kanteen:

I can put 4 pens+ with more cartridges in the wide mouth bottle, enough for 2 weeks with plenty to spare. As a note, the 20 oz bottle is the shortest bottle that will fit any size insulin pens - the smaller one, 16 oz size, is not tall enough to fit some pens.

For this experiment, I put 2 pens into the bottle (the bottle had not been cooled to start with, it started at 78F inside ambient temperature). I added 9 pieces of round plastic ice that I had previously frozen:

This is what the whole thing looks like inside the bottle:

I closed the bottle and put it outside in the shade, and left it there for 24 hours. The temperature outside started at 79F and went up to the mid-80s until evening, at which time it went down to about 60F. Today it went back up to 80F when I took it back in after 24 hours outside. After 24 hours of exposure (admittedly, the temperatures weren’t that high), the temperature inside the insulated bottle was still at 35F (see picture above)! The ice balls were not frozen anymore but they were still cold.

Here is a list of the components I used:

I am optimistic that this setup will withstand a full day in the heat! Any ideas about improving on this?


Michel, I think you have a decent design there by cobbling things together. If I was designing from scratch, and using something like a 3D printer to help, I would design a central frozen cylinder, or tube that would hold your frozen balls, that would allow everything to stay upright. Then you could probably fit more pens in, or perhaps find a smaller thermos to hold everything.

I am assuming that you have discounted the Frio due the humidity, which makes sense, however I would bring a Frio in case you don’t have access to a freezer and want to go a little lower tech.

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You are correct, @Chris, given the humidity, I expect the bag will not able to achieve any cooling (its efficiency dies off around 85F). But they will carry one just in case.

Your central cylinder design would be great!

You should be able to calculate the efficiency of the frio at any given temperature and humidity levels like calculating the relative humidity from a wet bulb thermometer (like you used to do in the navy) in reverse. E.g. Enter the relative humidity tables with the temp and humidity known and backtrack it to find the wet bulb temp

I like the thermos idea… I’m trying to scratch my head and think of any other alternatives to the plastic ice cubes

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Nice idea! I just took up your challenge and published the limit conditions for the Frio bag here. Unfortunately, they make it clear that my son needs the thermos where he is going!

Depending on the enviromental challenges I use either a Frio, a zip wallet with chilled inserts or a Contigo thermos with the same chill pack placed inside. Works great! Here is a link to the packs:

Here is a link to the wallet thingie so you can get a better look at the chill packs.

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@mremmers, welcome to the forum!

We have a similar wallet to yours, and find it really useful too. What Contigo thermos have you used? Do your packs remain flexible when frozen?

The packs we use for our wallet freeze hard and are not usable in a thermos. In fact, I have another experiment on the way to make small flexible packs that can be used in a thermos:-)

I use this one. It’s a 16oz size and is shown in the photo. The Lantus pen makes it a tight fit though in terms of height. If purchasing this thermos with insulin cooling/transport in mind I’d get the 20oz version. The packs can’t be bent when first removed from the freezer. 18 hours later they are still cold but bendable.

A link to the 20ozer:

My setup:


Of course if you want to be a macho macho man you have to get the Stanley Classic

I am picking out a thermos for youuuuuu
Not an ordinary thermos for youuu
But the extra best thermos you can buy
With vinyl and stripes and a cup built right in

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I used to own one of those many years ago! It may still be in the basement for all I know…

I have one at my parents house I just told them to dig it out for next time I see them after this thread

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I had to do the same with the Klean Kanteen: the 16oz is about 1/8 to 1/4" too short for the longer pens. The 20oz works well on anything. Both are exactly 3’ diameter btw, to compare with your excellent picture.

FWIW, I used a thermos bottle back when I was first diagnosed more than 40 years ago. It was a pain because the ice would melt and make the bottles wet, labels would come off, etc. This was before the days of plastic ice (and plastic labels on the bottles), so you’ve found a fix for that problem, but you’ll have to figure out how to re-freeze those ice-cubes during your travels, which may not be easy.

Anyway, I later realized that it really isn’t necessary to refrigerate insulin, and since then I’ve never bothered and never had a problem. I spent a couple weeks in Costa Rica and Nicaragua a few summers ago with my son, in non-air-conditioned hotels, and my insulin was just as good at the end as it was at the start. I kept my spare back-up bottles in the hotel, and carried my open bottles with me at all times, out walking around in the sun (with some volcano climbing thrown in there).


That’s great info! Did you do anything to keep the open ones in shade?

A few months after my son was diagnosed, we turned down a chance to trek in the jungles of Guatemala because I was afraid his insulin would go bad (no access to ice there where we would have been). I figured with high humidity I would not be able to use an evaporator. I still want to make this trip happen though!

So happy that worked out for you and good to know. I’m not so daring so when I was spending 14 days around the Mediterranean I used this setup. I’d cool the pack and the thermos in the room refrigerator (on board a ship) at night and was good to go all day. And there were some really hot days and no shade, like in Pompeii and Ephesus. When I’d grab my syringes they were always cool and I didn’t spend any time worrying about them. But, agree, it only works days in a row when you have access to a refrigerator at night. Or ice. In a pinch I’d use ice and stick the pens in a zip bag inside.

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The bottles (Levemir and Humalog) weren’t directly in the sun since they were in a soft-sided case in my pocket, but I was certainly hiking in the sun a lot. Eric posted about testing insulin in even more extreme conditions:

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if i am traveling by car for 2 hours with the a/c on, and i have as of yet unopened insulin in my bag, should i need to worry about it not being refrigerated for that brief period of time?

i noticed that when i was wearing my pump at the beach, i would turn the pump to hook up to the backside of my bathing suit so it wouldn’t cook. of course, it did get hot, but nothing seemed to influence its strength once it cooled back down.

just curious.

I don’t think you have anything to worry about.


So my son has been “there” (the NW coast of Costa Rica, near Samara) for 4 days. He and my wife are telling me that the Thermos solution works great so far.

Temperature has peaked between 90 and 100 every day, and humidity is at the same level (85-100% every day) – so for sure the Frio bag would not have worked.

That said, it is very possible, based on @Eric’s and @jag1’s experiments, that his insulin would be fine anyway.

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I like the ideas in this thread. I’m going to be travelling for two months in a couple of weeks, and while it’s not going to be super hot, I’m going to be bringing about three months’ worth of insulin plus some allergy serum (I’m doing allergy shots, and that stuff really does need to be kept cool) plus some food that needs refrigeration, so I wanted something that would keep it cool during my day of travel. I bought a Pack It cooler that has bult-in ice in its sides and is supposed to keep things inside cool for 10+ hours. I haven’t tested it yet. I was planning to add some extra ice to it, and I like the idea of the ice balls to use up little pockets of empty space.

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