If it's too bad, drop to 250mg only once a day (probably night, if that's the meal you find easiest to ensure is low-carb), and when side effects have settled, go back to twice a day and work up from there.

I had terribly trouble with some of my arthritis meds - I had to increase by smaller increments, and take longer to do it, and sometimes I even had to alternate dosages for a while - eg 1 tablet, 2 tablets, 1 tablet, 2 tablets, 1 tablet, 2tablets, etc until I could finally cope ok on the 2 tablet days. It may take a little longer to get everything working if you have to do that, but it should make life a little easier.

BW