Cold weather change insulin needs

Okay so first real winter with my cgm. Basal rates as of two weeks ago seemed pretty spot on. Wasn’t rising between meals and wasn’t being pulled down either. Great!

I live in the lovely state of Minnesota and we’re starting to get chilly. It’s put a damper on the daily walks I usually take spring-fall, but I have supplemented with more activity to off set that like a half hour on the elliptical, weight lifting etc. Even with keeping my activity level generally about the same and I’d even argue a bit more aggressive and sticking to the same diet I eat the rest of the year I’m now starting to notice a bout of dawn phenomen and just rising between meals which indicates I need to do some basal testing again.

In theory, nothing has changed. I don’t feel ill and I’ve ruled out other things like UTIs that are unsymptomatic for me sometimes. Not feeling stressed or anything I know can impact my sugars.

Can literally just the temp outside change your basal needs even if your routine has stayed pretty consistent? I know your body wants the amount of insulin it wants and I’m not scared to take more- it just feels so weird when nothing has really changed and all the sudden it’s not enough.

I typically have to do some tweaking a couple of times a year due to the seasons.


I had no idea this was a thing! Okay well looks like I’ll be doing some basal testing. Do you find your IC stays pretty consistent or that needs some adjustment too?

It seems like the twice a year seasonal used to ride me over pretty well for the long haul, but I seem to make more periodic adjustments now, maybe due to age, new exercise regimens and other factors. It’s been so long since I did just seasonal tweaks but I think it was my basals and my carb ration stayed the same. Do your basals first, then you’ll see if the carb ratios are still in line.
It sounds like you’re fairly new to pumping so I recommend you work with your doctor to adjust your settings. When I first went on a pump 30-some years ago I was excited that I could adjust on my own. I needed to dial back some of my insulin but maybe hadn’t gotten any guidelines so I cut back by a full unit😲 and started going sky high. Turns out a fraction of a unit - in my case even 0.1 - can make a world of difference, so start small. You should keep your new settings in place for 3 days or so to give time for them to settle in - unless of course you have problems with extremes you can’t otherwise account for.

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Same. Right about December and April. For me it’s just basal.


Sadly I’m not new to pumping. Until this year, I never made adjustments to my basal by myself (endos always asked me to touch base with them before doing it). Well I lost 60 pounds this year and obviously with that had a ton of basal changes and now my endo is kind of sick of me so they finally gave me permission to do what I want to do which is dumb because I now realize I should’ve been doing that the whole time. My A1C has went from mid 7s to mid 6s by trusting my instinct and doing temps and basal adjustments as needed :joy: totally agree with the .1 unit. I started really small and went from .75 to .8 overnight. First night seemed to strong but I did work out in the evening versus morning so not counting that as data. Last night went to bed at 136 and woke up this morning at 124. I rose a little bit overnight to 148 but stayed very level for the most part. So if this continues the next couple of nights I think my overnight basal is good again! :slight_smile: thanks for the tips!

Okay great! And I’m assuming in April you typically see a decrease in your basals again? Thanks for the info!

@Tee25 yes. The funny part (funny to me anyway) is my endocrinologist INSISTS that my basal requirements SHOULD GO DOWN in December… not up… so I stare at her, without saying a word, until she changes the subject.


Congrats on those overnight numbers! I love to see an almost flat line in a good zone. Seeing a flat line on medical equipment generally is not good news but here is an exception​:blush:. Glad to see your doctors finally realized you could and should tweak yourself. Uh - should I re-word that​:thinking::blush:? Much better for you and for them. Now I’m wondering how they got that “December drop date” idea - where in the world did that come from? Another medical mystery…

I’m with Dorie: why in the heck would insulin needs go down in December? For us, there’s no question that hotter=less insulin, colder=more.

@wadawabbit @srozelle her thinking, and I quote, “in colder weather you burn more calories staying warm so your insulin needs should go down” and again - I just stare at her because the comment isn’t relevant to my rising blood sugar. Now mind you I make all of my own pump changes, so I’m not asking her, I am merely informing her about a basal rate change I already made. Sometimes I have to forgive the doctor… she has only been practicing medicine for 20 or so years, and I’ve bene practicing (on myself) for 42.

I might also add that somebody, somewhere, probably needs more insulin in colder weather. Its the very nature of this disease there are no hard and fast rules.


So interesting! I mean in theory, what she’s saying makes sense but still funny that she’s so sure of it😂

I’ve come to realize that endos (and doctors) are all very textbook and they have a hard time wrapping their head around unique individual differences. Mine gets frustrated that I do temp basals after a work out but depending on how hard it is, sometimes I just need less for an amount of time and they just can’t believe that I might need a different basal for different things.

Good thing we’re all good doctors :blush:


@joe - I agree. I’m just saying is not like things automatically chance when we flip the calendar.

@wadawabbit I agree too. In fact I always forget to dial back in the spring until a certain someone asks me why I’m so grumpy and irritable. Then I see I’m low a lot. Maybe I should set a calendar reminder. :grinning:


Thanks for this conversation - it made me realize that I needed to make a change in my basal since it is colder here in the Boston area. I got diagnosed in June of this year and a lot of this new to me. These conversations are so beneficial because what the ‘old pros’ take for granted, us ‘newbies’ think is brilliant!

I am not a pump user but I understand the concept is the same. Thanks for the info and keep it coming. You never know who is lurking on these forums :wink:


I might have missed this but if nobody has suggested it check out the book Think Like a Pancreas by Gary Scheiner. Really good information for people recently diagnosed as well as a refresher for those of us who have been doing this a while. The author has Type1 and works in the field so he has a unique perspective.

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Sorry I’m in on this one late.

I suffer Seasonal Affective Disorder. Lots of people say that, but in my case I need a prescription for it and I consider it right up there with insulin in terms of which of my meds saves my life most. my med changed my life.

There’s 5 places in the year that I can count on my whole being changing, even with meds, and I have to work as hard on making sure I don’t just retreat to my bed and pull the covers over my head for 16 hours a day as I do on making sure that my blood sugars and food intake and insulin consumption are in sync. Usually, Thanksgiving is the absolute pit. It’s when my body is saying loudest, “HIBERNATE, DAMN IT! IT’S GETTING TOO LATE TO START!”

And usually, every year my boluses and basals need to be maybe 10-15% higher at all times. So my input is, do all the things that a seriously Seasonally Affected person finds helpful:

  • Get sunlamps and sit in front of them for an hour every morning. On gloomy days (and I’m in Maine, we get them), for the rest of the day make sure windows are open to the sun (uh, closed, but all curtains and shades shoved out of the way), and keep maybe more ambient lights on than you normally would. Light. You need light. The light subliminally encourages you to move around more. That helps your metabolism stay engaged and your basal stay more normal.
  • Every day that’s sunny, get outside in the sun as much as you can, because the hours are shorter and you need to make up for sunlight hours being stolen from you,
  • Be as active as you can. Exercise more, unless you were already doing way more than the average person, but more as much as possible, and outdoors as much as possible. Exercising a ton in a dark gym is not the same.
  • I’m on more vitamin D now, 3000 IU or 75 mcg/day, and it seems to be having an effect, but I don’t know of any studies about this. I’m just bearing in mind that even if you’re outside more, the sun is more filtered and you’re getting less vitamin D than you would with the same amount of time outside in summer.
  • And sadly… so far this year is actually the best year I’ve had, ever, and I’m perplexed, but the one thing that’s different is that I haven’t had a single change to my diet - even over Thanksgiving. It’s so easy to think that you’re compensating adequately for any extra bite you take, and historically I do plenty of that even when I think I’ve been pretty good. But remember that at this time of year that food has a lot more FAT in it than at any other time of year. For me, it’s fat content that really makes my BG slow to a crawl. Sugars, schmugars, I can compensate for those, but add extra butter and I’m having trouble. As much as I watch my carbs when I eat, I try hard to watch my fat intake, it makes all the difference, and the type of fat makes even more difference. Olive oil, not such a problem. Milk fat??? O. M. G.

And there is no other time of year that we really go out of our way to make foods as fatty and buttery as they can get. And invite each other and stuff their faces, too.

This year I’ve done a lot better job about being outside more and eating absolutely nothing I that I don’t already the rest of the year, and like I say, I can’t say whether the increase to my vitamin D is helping. I always got tested for D once a year - ironically in January - and it was always just below minimum, even on 2000 IU/day. Now it’s 3000/day and my D is finally about 1/3 of the way between minimum and maximum acceptable levels. Is it a factor??? No idea.

Not to go off topic my PCP recently told me I have osteoporosis and recommended supplements. As I was researching calcium and Vitamin D I read that it is possible to get too much Vitamin D so just wanted to recommend people get guidance their physician - as you did - about how much to take, since more is not always better.

Absolutely. I listened to a medical podcast (Pri-Med, given by doctors for doctors and aspiring medical professionals) a year ago when a geriatrics doctor was saying, older people need more D and he has no problem with prescribing 3000 to a senior, but that the maximum anyone should ever take is 4000 IU (100mcg)/day and only if circumstances warrant it. I went to the pharmacy the next day and noticed that they came in 2000 and 5000 IU. Vitamin companies are so … obnoxious.

But D is a vitamin that lasts a long time in your body. When I first started I was on a monthly dose, one very high-dosed pill per month. (Try to get insurance to pay for that now! LOL) You could take 5000 IU pills as long as you only take them every 2 or more days. You just shouldn’t be averaging more than 4000, and from what this doctor said almost none of us needs that much - there being always exceptions to the rule, of course. Even I, with my historic chronic low vitamind D, am not such an exception.

Absolutely consult your doctor, as @wadawabbit Dorie says.

And as I say, my PCP tests mine every year and I don’t complain, even though on my insurance plan it’s not cheap for me. I know that I’m naturally low on D and have been since the first test in the 1990s when I was outside walking 10-15 miles a day, theoretically getting all that vitamin D from the sun. I have no idea if that’s part of the acute Seasonal Affective Disorder, it’s something I’ve wondered.

And again, this is all in the context of insulin not going as far in colder - darker - months, and my not knowing if my increase in vitamin D supplement has anything at all - or nothing - to do with why I’m having a better year this year than usual. “Better year” doesn’t mean that this year I’m jumping around full of energy, I’m just not holing up in bed with the covers over my head, simulating a hibernation den, and stuffing myself with fatty foods. Maybe I was a polar bear in a previous life.

Never looked it up, did I.

From the NIH’s National Institute of Mental Health page on Seasonal Affective Disorder, under Vitamin D:

“Because many people with SAD often have vitamin D deficiency, nutritional supplements of vitamin D may help improve their symptoms. However, studies testing whether vitamin D is effective in SAD treatment have produced mixed findings, with some results indicating that it is as effective as light therapy but others detecting no effect.”

Light therapy is always the first treatment that should be tried. I have also read in many places that the earlier in the day that you can get this light exposure, the better, and NIMH confirms, “usually first thing in the morning.”