TuD member, @2hobbit1, posted this info about the diluting insulin. She used diluted U50 insulin that she mixed herself.
Making U50 is simple - one vial of U100, one vial of diluent, two 5cc syringes, use the 2 syringes to take 5cc from each vial, then swap syringes and return to vials. It makes 2 vials of U50, they will keep in fridge for about a month and a half before starting to deteriorate.
She also offers this advice about dosing with U50 (diluted U100) insulin in a thread entitled, Low dose insulin challenges and low carb diets:
Hi all,
Yes I pump U50 Novolog. NovoNordisk is still making diluting fluid for its novolog. Not sure if the diluting solution for Humolog is still available.
The diluting media is the identical solution/preservatives etc that the standard U100 is made in. It is only available to your Endo, from NovoNordisk. You endo must fill out the paperwork to get it shipped to their office. It has a similar shelf life and storage conditions as the novolog does.
Making the dilution is fairly simple, once you get your endo onboard. It simple requires a script for the 5cc syringes and needles required to do the exchange/dilution. Once made it has the same stability any other open but refrigerated vial of insulin.
It takes some thought and initial math to change from U100 to U50.
For every 1 unit of U100 you will need 2 units of U50. Also if your U100 I:C ratio was 1 unit per 10 gm of carbs, then for U50 you will need 1 unit per 5 gm of carbs. Correction factors are also half of your U100 crew so if using U100 your CF is 1 unit drops your BG 100 mg, then 1 unit of U50 will drop you 50mg. Your duration of insulin activity is still the same.
You will need to work with your endo on the math involved with marking the switch, and how to do the dilutions. Once it’s set, then there is no additional mental math other than accurate carb counting.
Doing basal and bolus testing will still be the same.
This would require syringes for MDI, since U50 is not available in pens. Depending on the type of syringe your doc writes for you can get unit markings that allow quarter unit approximation. If you add that to U50, you should be able to micro dose.
So, other people with diabetes and children with diabetes have diluted insulin before. It requires the cooperation of your doctor and getting the correct diluent from the insulin maker.