I seem to be pretty sensitive but I think that's partly because it's early days for me. The other night I was at 16mmol so begrudgingly took a 1 unit correction dose. Two hours in I was down to 12, and with it still having two hours or so of action I decided to eat a biscuit just in case (~9g carb). Two hours later at the end of the insulin action I was at 10, so with 1 unit of insulin and a biscuit I dropped 6mmol! Without eating I probably would have dropped about 8mmol, which seems a lot.