How to adjust insulian according to HC

Hello again!!!!
To date we have not had a problem with my daughter's HC intake, which already seemed strange to us.But for a few days yes, for her HC 8 in the food and 6 of HC it is too much ........... with the 4 of breakfast and 2.5 lunch and snack at the momentWe have no problem (they are the rations that his pediatrician paid him).
Of the initial doses of insulin we have passed to 14 of Lantus and between 3.4 or 5 quickly depending on how it reaches the meals and thinking about the activity that will be done later, and usually not putting any at lunch and in theSnack, reaching each control quite well, so we have been able to avoid the hypo that had at the beginning halfway tomorrow and half afternoon.
More or less, or so we believe, we know how to adjust the rapid insulin doses before each meal, but starting from the HCs guided, but we have no idea how to adjust insulin if we reduce HC.
We have seen a lot of formulas out there but we don't finish seeing it clear, I don't know if someone can help us.Her pediatrician told us that those amounts were the ones she needed according to her diet, but we will try to make the day that we have visit us, to date if you can help us would appreciate it a lot .......

What works best in this is experience.Trying down one quickly and measures later ..
If you reduce hydrates by half, you will need half fast ..
It's a matter of testing ..

Thanks Regina !!!!
I will try to agree with my daughter what is going to eat and calculate the HC that you will take, and according to the prescribed HC and the insulin that corresponds, calculate ...... with the little time that I have been with this there are moments that me that II lose ...

Little by little ..>: D <

You can start with a rule of 3, if for example at noon you put 4 fast for 8 rations of HC then it needs more or less 1 unit for every two rations of HC with what for 6 portions for example, I would need 3Fast units.If a rounding number does not come out (1.5 units x ration of HC for example) you will have to adjust above or below depending on its glycemia value before eating.
And above all, as @regina, test and error says.