I was told years ago that for every 1 over what you would expect your bg to be inject half a unit of insulin extra , Indeed this morning I wakened to a bg of 16.9 so injected 5 units extra and went for a walk , Two hours later and after my 30 carbs for breakfast it has come down to 7 , Works every time for me .
So I guess that means you have a correction ratio of 1 unit of insulin to 2 mmol/L. Bear in mind that correction ratios can also vary drastically between people, (eg my nurse told me to divide 100 by my daily insulin total as a
starting point for how much 1 unit of insulin would bring me down), so this is yet another ratio that has to be calculated for the individual.
@grahamrb I can only imagine what a shock it must be to get a T1 diagnosis at 78, so it's sounds like you are doing an awesome job at working out what to do. Just remember insulin ratios can change, and here's a link to bertieonline which is a useful T1 resource.
www.bertieonline.org.uk
And don't hesitate to contact your diabetic team to get advice. Though we can give you moral support and information here, we are not doctors and don't know your wife's medical history. Dosing advice needs to come from your team.
And one more proviso, at 78 hypos may be a lot more of an issue than at 28 or 58, so your team may (or may not) want your wife to run at higher levels than the younger T1s on these boards. Hopefully they have given you advice on this. If they haven't I urge you to talk to them.
@grhamrb, can I ask (feel free to ignore the question if it is too personal), are you a carer for your wife (ie making food and dosing decisions for her)? Hypos become even more of a potential issue if the person suffering from them is unable to deal with them without help...