How much i can take ashwaganda in a day

How much i can take ashwaganda in a day I read lot of become fluent after taking it for weak or two cause it's reduce stress that make u stutter , how much in day i can take without side effect like is 500 mg ok or 1 g , if i take only 500 mg i can help it with magnesium, cause i read ashwaganda have side effect like make u sleepy or stomach issues if u take a lot