i guess u can try it out yourself and judge at which ISO level the noise is intolerable to you. it varies from person to person
take photos at ISO100, 200, 400, 800, 1600, 3200, 6400 and see until which is still OK for you. don't need it to be so complicated with tripod, controlled lighting etc. just a simple snap inside your room is adequate.
but while trying high ISO for noise, make sure the situation really is dark and require the high ISO to properly judge the noise. if u use high ISO when it's bright where low ISO will work just fine, normally it'll show less noise in the high ISO pic