Tracking Insulin’s Health in the Summer Heat

Sunscreen: check. Water bottle: check. Beach ball: check. Insulin cooler….? Yep. For those of us who use insulin, summer heat creates an extra level of complexity and worry.

The real question we all ask ourselves in the heat of the summer is whether our fun-in-the-sun will cook our insulin and leave us having-not-so-much-fun in an air conditioned ICU unit?

There’s a whole industry of solutions dedicated to helping us keep our insulin cool, ranging from cooling packs such as the ReliOn and others, to portable fridges, to high tech cooling crystals. Hell, we’re even running a Giveaway contest this week in which our readers can win some of these products!

With much of the U.S. suffering under a stifling drought-baked summer, the question of just how hot insulin can get is on all our minds. But you have to wonder if these products are serving an important need or just preying on our fears.

To find out, we asked the manufacturers themselves, some leading insulin experts, and the American Diabetes Association — and guess what? The answer isn’t as clear as you might like.

Not Your Grandma’s Insulin

First, a bit of history: Didn’t grandma keep her insulin in the fridge all the time? Well, only if she read the label. The original pork and beef insulin formulations were supposed to be kept cold all the time. As cold insulin stings like hell to inject, the move to being able to keep the newer human insulin and later analogs at room temperature was a great victory (!) for those of us who are human pin cushions.

But wait a minute… whose room temperature are we talking about? My father used to get annoyed with me when I’d shovel ice cubes into my glass of red wine. “Wine is supposed to be consumed at room temperature,” he’d huff. “Yeah, in the frickin’ French Alps,where room temperature is, like, 50 degrees,” I’d snap back. “I live in New Mexico. Here, room temperature can be 90 degrees!”

The rising temper of that discussion was sometimes enough to heat up the room itself…

These days, room temp requirements for most opened vials and insulin pens fall between 36° and 86° F. So says the official literature that comes with basal insulins Lantus and Levemir, and rapid-acting Humalog. Interestingly, it’s also the temp range for good old “R” insulin.

NPH was to be kept mildly cooler at 77°, along with new-kid-on-the-block Apidra. Novolog is the tough character in the bunch with a max label temp of 98.6°. More on that later. Unopened vials and pens are to be stored in the fridge between 36-48°, a temperature range that hasn’t changed since pork and beef insulin.

By the way, for our type 2 readers: Victoza uses the same magic 86° room temperature; while Byetta clocks in at an ideal 77°.

From the Manufacturers’ Mouths

So much for the labels. What’s happening in the real world? We contacted Novo, Lilly and Sanofi to speak with their insulin experts — though we only got as far as the official spokespeople.

Susan Brooks, the senior director of communications for Sanofi’s U.S. Diabetes Division, emailed us part of the prescribing information sheet. I already told you what that said. And that pretty much sums it up from her.

Meanwhile, Julie Herrick Williams, communications manager for Lilly Diabetes, answered some questions via email

Image: shuishi.org

(complete with a full barrage of ® and ™ symbols). Translating to English, she says that the old school insulins and more modern ones have “similar storage and handling guidelines,” which is true at least as far the as the labeling goes. Again, more on that later. Most of her info seemed to be verbatim from the package insert as well, but she did add: “People with diabetes must take appropriate measures to store and transport their insulin to ensure the product quality is not adversely impacted.”

Um, yep. No kidding.

Moving on, Novo’s Ken Inchauski stated several times that he’d try to locate answers to our questions. He didn’t get back to us by press time, although we gave him two weeks. Pity, as Novo would have had the best perspective on the separate issue of temperature comparisons between basal and rapid-acting insulins vs. GLP-1 drugs, as they are the only company to make all three types of meds.

Hopefully, we will get an update from Novo about all this — ”straight from the horse’s mouth,” so to speak.

What the Experts Say

Ok, it’s time to turn to the academia and medical professionals who are actually in the trenches prescribing this stuff and dealing firsthand with patients’ questions about insulin temps (among other things).

At a recent diabetes conference, I informally polled a number of leading research docs. I’m not quoting them here as I was attending in my Superman clinical identity, rather than my Clark Kent alter-ego. But their universal answer: “Tell your patients not to worry about it!”

Seriously? They didn’t think there was any difference between modern insulins and earlier formulations. When I asked each one where the whole “keep your insulin cold” message got started, they didn’t know. I also asked several if animal insulins were more sensitive to heat than human insulin, and none could remember that far back.

Just more proof that medicine is an art, not a science!!

Insulin, Eggs, and Snow Globes

However, closer to the trenches, the view is different.

Geri Spollett is an advanced practice nurse practitioner with the Yale Diabetes Center, and the President of Health Care & Education for the American Diabetes Association. In her experience of being in the biz since 1978, the older formulations are more stable temperature-wise than the newer analog insulins. “I think that the modern insulins tend to be more sensitive to heat,” she says. (Good news for those of you forced by lack of insurance back onto Wal-Mart “R” and NPH!)

But with that said, Spollett advises all her patients to store unopened insulin between 36-46° F in the fridge, and to keep the active vials or pens under 86° at all times — pretty much what the prescribing info sheets recommend. She also feels that GLP-1 meds seem to have about the same sensitivity to heat as insulin, and she instructs her patients who use these meds to use the same protocols as her insulin users. And unlike the experts, she spends a lot of time worrying about her insulin-using patients in the summer.

She feels that even brief exposure to higher heat can affect insulin. Spollett points out, “Insulin is a protein, like eggs. Protein changes composition with high heat.”

Paraphrasing: if you heat an egg, it cooks. So, too, does insulin.

Spollett says that insulin affected by heat becomes gradually less potent, a slipping effect that sends blood glucose numbers gradually upwards, with boluses and corrections becoming less effective, rather than a more dramatic effect. Although she notes that in the past, with poorly packaged mail-order insulin left on door steps in hot climates, it was possible to get “outright bad insulin”; this issue seems fixed with improved low-cost shipping coolers.

She also mentions how some of her pumping patients have asked to switch from Humalog to Novolog during the summer because of Novo’s label that says it’s good up to normal body temp. But she’s never seen any clinical or anecdotal evidence that Novo is supposedly superior. Maybe, it’s that the company just thought to add the 98.6 temp to their insulin FDA application when others didn’t?

So, can you recognize “bad” insulin? Most experts say “no,” and that the only way to know is in how it works. Spollett acknowledges that heat-affected insulin maintains its water-like color, but says that careful inspection can show a “frosty appearance.” She states “it’s not like a snow-globe, like old insulins, but you can see very fine particles” suspended in heat-affected insulin.

She’s quick to add that she thinks very brief exposure to elevated temps, like walking from a car into a building through high temperatures is unlikely to have an effect. But she worries about her more than 220 pump patients who spend more time outdoors in the summer, exposing their pump-encased insulin to high temperatures, and even to direct sunlight for extended periods of time. She urges her patients to take measures to shield their pumps from sunlight and even to consider using cooling technology of some sort if spending time on a beach or at a similar venue.

(Hint: Don’t forget to enter our insulin cooling system Giveaway before the deadline on Friday!)

Thoughts From a Hot Climate

Personally, I live in a place where outdoor summer temps often top 100° (in the shade). So inside, mid-to-high 80s isn’t uncommon.

I put ice in my red wine, but do I put my open insulin in a cooler? Actually, no. No I don’t. And I don’t spend much time or effort worrying about heat and insulin for myself. Of course, I wouldn’t leave an insulin pen in my car either.

And even though I might not be as proactive in protecting my insulin as providers like Spollett might like, I did like her bottom line: if your insulin stops working the way it should in the summer, don’t futz around trying to figure out what might be wrong; just throw it out and start a new pen or vial!