Depends how high! The rule I was told was that 1 unit of novorapid will lower your BG by 2.5 mols over 2 hours. It seems to work quite well for me but you know what they say, everyone is different
I took 2 units at BS of 22.5 and 3 hours later I was at 6.0 and thought that was a big drop for small amounts of insulin, but then I do seem to be very sensitive to insulin as I am still honeymooning.
The generally accepted rule is 1unit of quick acting insulin will lower your blood sugar by 3 mmoles/litre but as johnar says everyone is different. Taking 2 units and dropping from 22.5 to 6 seems a bit drastic but it depends on a few things like how soon after you ate did you test and take your correction dose and after you made the correction how active were you.
So you just need to experiment for a while. There is however a strong view (that I don't always follow) that says don't correct between injections because you may get additional problems because of overlap of doses and potential increased risk of hypo.
Good luck.
