Will definitely let you know how I get on
@Wonky, because your basal is Tresiba, be cautious of the siren voices encouraging you to do basal tests (plural).
Tresiba is a very long acting insulin - unlike any other basals. It's profile is claimed to be 40 hrs and that fits my experience, as best anyone can tell. This means today's dose is topping up yesterday's dose and gives Tresiba the potential to be very stable as well as making it inflexible. It has been likened to the user being the Captain of a super container ship on a 3 day crossing of the Atlantic, which needs 2 day's notice for a course change to take effect. This inflexibility can be a benefit.
One's body receives glucose from our liver's glucose store at all times of the day and night in response to an array of hormones that results in the liver releasing glucose. Most of those events happen regardless of anything you or I consciously do and the quantities of glucose released varies a lot. So the basal insulin required is irregular across any one 24 hr period, but despite that irregularity it is possible to identify one's own individual patterns and normal basal tests are frequently done against nominal 8 hr fasting periods. Not so with Tresiba - it releases the insulin evenly (as you might expect) and because of the 40 hr profile and the consequent daily topping up it has very little start up or taper off behaviour. It's just always there. So for most people we optimise our Tresiba to match the need of late evenings and through the night, when we are in effect naturally fasting (and when beauty sleep is important and low alarms are a complete nuisance).
The only decision the user initially needs to make is to mentally identify what is their normal night fasting period - eg 11pm to 7am - and their normal overnight routines. Then from CGM graphs and with no out of your ordinary night snacks or late evening meals you optimise your daily Tresiba dose by adjusting the dose until your Tresiba keeps you steady through the night. Tresiba dose adjustments can need 3 days to take effect, so don't make changes more frequently than that and ideally 4 or even 5 days. Once you've found the dose that keeps you steady(ish) and from which you start and finish in about the same place then that completes the basal testing for now. If you start and end higher than you wish then adjust by bolus correction or exercise to get to a better starting point. Likewise if lower than desired adjust bolus ratios or take an unbolused snack accordingly.
All other parts of the day you can only regulate your BG by the appropriate mix of carbs, bolus and activity. Whatever Tresiba is contributing to help daytime background insulin needs is happening and can't be adjusted by Tresiba changes. For you
@Wonky this won't necessarily seem unusual. For individuals who are new to Tresiba but who have grown accustomed to using any other basal with shorter profiles (possibly with years of this experience) they could find the idea of not making frequent basal changes uncomfortable and possibly unacceptable. Tresiba is different; and in the last 2+ yrs I've encountered all sorts of HCPs, including DSNs, instructing me to change my basal dose when that would simply be wrong.
That said you will need to alter your Tresiba doses from time to time. Right now I have a wretched head cold and cough and I've increased my daily Tresiba from 8.5 to 10 units, since it's been noticeable that several nights in a row my BG has steadily risen; this increase is also helping against the daytime increase in my BG because of this coough and cold. I also expect my Tresiba to need adjusting for the change in weather from summer to winter. This latter seasonal change will be a process of trial and learning for me this year. We moved house at the end of July; we don't know how warm the house will be this autumn into winter and we are temporarily 5 in the house until next spring. So the occupancy level, the new heating environment, the temporary smaller bed and increased "snuggle" factor, etc, etc will all have some bearing on my personal insulin sensitivity as well as basal background needs. Also the increased occupancy is changing our daily routines including meal and bed times; so other things for me to keep in mind.
Once I've sorted all that out in the spring we should be back to just 2 of us here and no longer sharing heating bills - so more adjustments in lifestyle to come.
But this is also illustrative that quite often events change behaviours and timings for any one of us during "normal living"; and these changes can either regularly put the Tresiba basal out of kilter or explain one-off mornings after the night had not been so level! This happens to all of us, regardless of our best efforts and the essential thing is to recognise, accept, explain to self if possible, but regardless move on. Today will be different to yesterday.
