You eventually gain an instinct for it. Doesn't always work, but for me it works better than the formulas...
That is the most important part, you can really live a good life if you have that. I hope we get more powerfull and cheap way to do that continously. At the momemnt it's at least 300 USD a month for a CGM device that can measure every five minutes. It's abit like monitoring traffic load and adding more servers as you go, except too many servers kill you.
That with knowing how you react to changes in life works wonders, e.g. exercise, eating fat foods, sitting all day.
About devices.. The first Glucose-test-device (what are they even called in english) took 5min to process the results. Current one is 5sec. A massive improvement in both speed and accuracy in these things.
I hope a good non-invasive device is developed, though i'm not sure it is essential, for me anyways.
Not even just that, but with fairly primitive monitoring tools. The built-in stuff for Dexcom can only alert on highs or lows, not on things like the rate of change, which would be much more useful IMHO.
(When looking at the app, there are "trend arrows," also, but they unfortunately are misleading in some situations. Often looking at the data points can give you a sense of your situation, though.)
The official one from Dexcom is not very good.
Even with import taxes/tariffs applied, I could imagine a vacation to Europe being massively subsidized by just bringing back one or two years of GCM supplies (obviously Vimes theory of socioeconomic unfairness[1] applies).
[1] https://www.goodreads.com/quotes/72745-the-reason-that-the-r...
Dexcom is the only one accurate enough to use with SMB looping. And the only one in germany that sends the glucose numbers to your phone with BLE. Libre 2 can be hacked to do the same though.
However, I was under the impression that the GP [emj] was "only" considering good monitoring to improve their decision about insulin application. Not a closed loop system. But yeah, if they meant a closed loop and if the Dexcom is the cheapest option here, then the 300 US$/month is actually cheaper than the 380 US$/month you outlined.
Also 30 years here. I have exactly the same thing as you describe though when I switch insulin I do start calculating again to be sure it matches with my assumptions. Blood glucose measuring is required though as you mention. I'm one of the lucky ones with very lineair and predictable response to every unit more or less of insulin. Not everyone is that lucky though.
To be honest, i don't do the math. I choose the amount of units to inject by feel. I mean, i know by eating a banana, i get something like 20g of carbohydrates, and i should take 3u. But if i feel, that the correct dose is 6 units, then i take that.
I cant really explain it. But i kind of feel the state, where i am going, and can adjust instinctively. Works more often than not. I have never passed out.
Edit:
I measure blood sugar A LOT, though.
Most important things are what i think as the Morning Gate, and the Night Gate.
For Night, must have blood sugar under 10mmol/l. Preferably without pending effects such as food or recent injection. If i get that right, the night blood sugar is steady.
In the morning, must account for the morning blood sugar raise phenomenon.