In reply to onlyhalfwayup:
As folk have said, great to see this article up and ace to see you're planning with your partner for some winter climbing. I'm keeping my finger's crossed for an epic Scottish season this year too.
As another type 1 who does a bit of winter climbing, I can also wholeheartedly recommend Jerry's input on this matter. After discussing with him the challenges of it, he is certainly one of my inspirations! Although every type 1 will have certain quirks and personal twists to their condition, I find the following 3 part structure really useful for a long winter climbing day.
1) The most important factor (as Ailsa mentioned above) by far, is dose adjustment of your background insulin. You get a feel for how much you need for a big winter climbing day and will involve some personalised trial and error, but I usually go with 15-20% of a non-active day dose depending on the size of the walk in. Compared to 40-50% of a non-active day dose for a summer multipitch day.
2) The powerful combination of cold temperatures, physical exertion and mental stress all drain your body's blood glucose supplies, so it's imperative to be well fuelled and insulin dose adjusted. Getting to know which food supplies work best for your partner will take a bit of time and is a whole topic on it's own unfortunately! For me, I don't like to stop that much when winter climbing, so I load up with a big non-carbohydrate based breakfast to account for my natural morning glucose rise before setting out; then I just constantly graze over the course of the day at belays/gearing up points or any static moment to keep my blood glucose in the 'green zone' and to avoid hypos. Every time I pause for any reason, I try to test my BG too. As Ailsa said in the article, I try to avoid injecting fast acting insulin over the course of a day in winter. Too many layers to adjust in Scottish winter and too high a consequence for any kind of error.
3)Finally, in order to test regularly your meter needs to work! The modern CGM meters are a dream compared to the old finger pricking ones I used to use, but they are still vulnerable so take a back up one too. My CGM is linked to my phone which I have in a cycling bum bag (fully charged at start of the day and with small spare power pack in reserve) which I have orientated round the front, inside my outer shell jacket and mid layer. This houses all my diabetic essentials and keeps them warm and functioning.
I could probably discuss this for hours and is too complex for a small post but feel free to get in touch if you want to chat about it. Good luck for the winter and hope it helps!