Thanks for writing your query to us.
Blood sugar levels of 400-500 is not good for your mother's health.
Kindly ensure that your mom is stricly following a daibetic diet & taking proper dose of antidiabetic
medicines on time regularly.
If still after increasing dose of antidiabetic medicine if the sugar's are not showing declining trend that any local form of infection needs to be ruled out.
1000mg of metformin
can give rise to stomach side effect. The dose of medicine needs to be gradually increased. That may help to minimise the side effect.