I didn't have total control at 400 m.g. so the doctor raised me to 500
m.g. per day, and now I have total control. He told me to feel free to
go up to 600 m.g. if I needed it during the Holidays  to make it
through, and gave me plenty of medication. The Glaxo Smith Kline web
site says that some patients may require up to 700 m.g. a day for total
control, but that doses above that have not proven to be effective.
Most of it is determined by the patients body weight and since I tip
the scales at 230 lbs. it will take a higher dose of medication.  I've
always been stuck taking a higher dose of most medications because of
my height and corresponding  body weight. Good luck at 400 because it's
generally better for your body to get by with the lowest effective
dose, but only your doctor can work out the risk-benefit of the dose he
or she decides is best for you. I hope 400 works for you, so you don't
have to punish your body with a higher dose! Happy Holidays and good
luck for the New Year.
Jim