I have worked pout the ratios as 5 to 1 etc and been advised by dietition that she worked it out by dividing 500 by 31 and got 16 to 1.
Where does this 500 come from? it seems to be plucked from thin air
The 500 Rule is a calculation that is used to start working out for Type 1 diabetics to say how much will 1 Unit of Insulin cover the carbs. This is called the insulin-to-carb ratio or simply carb factor. The problem with it is the assumption that the average adult consumes 500 grams of carbs every day. The formula is flawed in so many ways firstly you presume the person will eat this many carbs (never assume), secondly you need to have a pretty good guess at what the Total daily insulin will be ( again never good to assume)
Presume you have your Basal right.
Always have your Hypo treatment on standby.
All I can say Test Test Test and document,
count the Carbs and test your Numbers before each meal and document it.
As a example I eat my dinner early so most Bolus out my system by bed. I take my Basal at 9 Pm I check my blood glucose same time and I want to be be within +\- 0.5 mmol/L when I test before breakfast . That way I know I am covered overnight and also if I am not dropping to much at night I know I need maybe 5 gram of carb before bed if I am going to bed a bit low to give me a safety margin.
Bolus Test before meal ,
Calc the Carbs and Document, Before Breakfast ,before lunch , before dinner you should have circa same Glucose if you got your Carb/ Insulin right on prior meal.
For Example I am 15 gram / 1 Unit in the morning but by 11:00 I am 10 gram / 1 Unit and that is from testing documenting and working out over time
That number might change over time as Circumstance change. Each person has there own numbers we are not all the same.
Last but not least If you are going to exercise that includes walking , a quick link worth a read on the % Insulin reduction required
Always take your fast acting hypo treatment with you, it is no good at home or in the car.
https://excarbs.sansum.org/adjusting-insulin/
I hope that helps.