| Some type 2s can reduce their insulin requirements to zero, and maintain good blood sugar control through lifestyle changes (diet/exercise), with and without oral meds. Others have to use insulin as well/instead of oral meds.
For those T2 for whom it works, insulin can be used initially to get blood sugars down to acceptable levels, followed by lifestyle/oral meds management.
T1s are insulin dependant from day 1 or very soon after diagnosis.
The number of insulin units used varies enormously - there's no set minimum or maximum. We inject whatever it takes to do the job! But a ballpark figure often quoted is around 0.4-0.5U/kg/day.
I will inject as little as 1U at a time for a correction dose, and use less than 20U/day at the moment | 
What is the lowest insulin doseage? 
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