It’s Not the Heat, It’s the Insulin

It’s that time of year here in Michigan that makes me very happy. Summer’s here, which means that the flower gardens that make up a majority of our lawn — front, back, and side of the house — are just about ready to go into full-color mode. My wife and I are also three weeks away from a weeklong vacation at a cabin we rented in a national forest on the other side of the state. So I’m excited for what’s to come.


One thing that doesn’t thrill me right now? Having Type 1 diabetes and being on insulin therapy. I experience low blood glucose quite a bit more during the summer than at any other time of year.

I’ve written about this problem, or at least mentioned it briefly in years past; it never fails to sneak up on me and require days if not weeks of tweaking basal rates on my insulin pump to get my blood glucose back to the relatively consistent place it was during the winter and spring.

The conundrum I find myself in is as follows: With insulin pump therapy as part of the way I manage my diabetes, the insulin pump delivers a constant, very small amount of insulin into my body through the infusion set. This is called my basal rate. I can change this to fluctuate during a 24-hour period, because at different times of the day my body may require more or less insulin — depending on many factors — to keep me at or near my target blood glucose of 120 mg/dl.

Since January… well, from January through last week, I had my basal rate dialed in to where I knew, I just knew, that at any given moment I was doing well with my blood glucose control. Of course I still had to pay attention to the carbohydrates I ate and bolus accordingly for those, as well as continuing to monitor my blood glucose. But I was content — confident, even — that overall I wasn’t going to be too high in my blood glucose readings, nor was I going low very often (unless I made a mistake with a meal bolus).

Good blood glucose control requires an almost constant monitoring — every three to four hours when I’m awake. To achieve good blood glucose numbers, to keep a low HbA1c, there is no “coast” mode, at least not that I’m aware of. There’s no getting around this. Yet there are periods of time, be they a few weeks or a few months, where the diabetic gods get together and grant me a reprieve from self-monitoring hypervigilance.

This spring was that.

Now, though, I’m feeling the other side of that stable, blissful, blood glucose monitoring reprieve. The summer’s early onslaught of heat and humidity, as well as my activity out in it (walking the dog, gardening, etc.), decreases the amount of basal insulin I need in my body. I understand it as my body is simply burning more of those sugars naturally, so the insulin isn’t called upon as much.

But the insulin — that basal insulin — is still in my body, and it still wants to do its thing.

So what happens? My blood glucose goes down. And I experience more weird, wacky moments when I know it’s going down. I check the numbers, and indeed it’s around 65 mg/dl, or 71, or 82. Not really dangerous, not yet. But another corrective is needed—one that is in addition to taking in some carbohydrates to make the immediate swing back to a safe blood glucose.

The other thing to do, it seems, is simple: dial my basal rate back so that I’m not taking in as much insulin. True. Yes. Why didn’t I think of that?

Believe me, I did. And believe me, I do. And yes, I have the means to make these adjustments, and I think about it, try to figure it out. The truth is, I often feel guilty about having low blood glucoses (30 minutes ago I was at 65 mg/dl because of a walk this morning in the heat). To the outsider it may seem that because I have the means to control how much insulin goes into my body, the low blood glucose moments must surely be my fault.


Well, maybe. But come on. For those of you who are using an insulin pump and who take it upon yourselves to adjust your basal rates on your own (some people, I realize, only want to discuss basal rate adjustments with their endocrinologist), you know, or I hope you do, that you don’t make large adjustments at any one moment. I can’t just cut my basal rate back by half, say, because that runs a risk of really throwing me out of whack, and I could then go high.

But the real reason the low blood glucoses happen is due to factors beyond my control. There are so many variables that affect how my body handles the insulin, both known and unknown variables. The weather, or physical activity, or something I may have eaten and not taken into account. Or the ways that the body can sometimes — if not often — be a freakin’ mystery.

Often, then, a simple adjustment to my basal rate is anything but simple.

So the game continues. The tweaking of basal rates goes on. The monitoring never stops.

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  • Peter Mead

    “I understand it as my body is simply burning more of those sugars naturally, so the insulin isn’t called upon as much.” — not sure what you meant here. My understanding is you body is more able access the insulin in you and uses it a bit more efficiently. I don’t think we have any natural burning function.

    I’ve been going low more too. But as you say, there are so many variables that I am reluctant to fiddle with my pump basal or bolus more than it is (two time periods for basal and a fixed sensitivity and ratio that varies only once throughout a 24 hour period on the bolus). Bicycling, yard work, walks and “naughty” carbs all create more fluctuations than my own system. So I try and keep the pump consistant and tweak all the rest.

    It seems to work, but my A1C, three months ago was 6.9 and I am betting it is a bit higher when I test next week.

    I came off the sensor because 1) it takes up a bit of real estate (minor scarring) in my infusion areas that I didn’t want to lose over time and 2) I didn’t feel it was necessary all the time. It gave me some good insight into how I digest and when BG climbs (way after the two hour mark sometimes) and the effect of fats and proteins, etc. but once I got that I moved on. Maybe use it two weeks a year, perhaps. Not sure yet.


  • Linda Ascherman

    I, too, have had the problem of going lower in the summer. After a few trial and errors, my doctor and I have come to the point where I now set a temporary basal rate for days when I know I will be in the heat or doing more outside. I also have the “complication” of being female, and having monthly hormone changes affect how my blood glucose runs. It took a few times of trying, but we figured that by changing the basal rates no more than .5 at a time seems to give you a good idea of how much further you need to go. Hopefully you will find your rates quicker than I did! Good luck!!

  • Karen

    Hi y’all,
    I live in the Houston area, and it has been extrememly hot here. I do use the sensors all the time because I have hypoglycemicunawareness. But I too, have been experiencing more lows in the summer. I do think it has a lot to do with doing more outside, but also w/the crazy summer schedules; vacations, family reunions, bar-b-ques, etc. My endocrinologist even suggested disconnecting during exercising or other outdoor activities. I go really low, 46 mg/dl, when riding my bike or even the bike at the gym. And w/out any symptoms, it gets crazy!!! I just recently got back on the sensors due to expense, but insurance is helping out now. I’ve had tpye 1 for 30 yrs. But only been on the pump for 10 yrs. I love it and will never go back to 5 shots a day. I do hope that all works out for y’all this summer. Have a Happy & safe 4th of July! Take care & God Bless <


  • Janice

    Good morning,
    I also find my sugars go lower in spring summer and fall. I agree it is we are moving so much more than in the winter. Even if we still continue an exercise program during winter. Just the fact I run out to the garden for lettuce for supper makes a difference…if you understand what I am saying:
    I pray you are all enjoying your summer.
    God Bless

  • delma cunningham

    my husband is 77 and taking 3 shots at meal time of 15 to 20 units of insulin of novolog. Then takes 40 units of lantus at night. 3 times this past week he has been working in the yard and feels the sugar numbers are low, comes in to check it and it will be in the 60’s. Does he need more insulin at noon or less to stop this drop. Or does he need to eat more food at noon. He eats a full meal at noon time. Today it happed at 3:00 p.m. I am not sure if he should increase the insulin or decrease the insulin.
    Thanks for the help.