400-500mg of Magnesium is daily recommendation. Most people are deficient (and need more then recommend daily intake) in magnesium and you shouldn't be worried about overdosing if you spread those 500mg through day. Some forms are badly absorbed and/or can cause diarrhea in large doses. Search this subredit for B1 thiamine, it was mentioned many times and I can't remember dosages(I guess it was 300-400mg split to three doses, but I'm not sure), but it was safe even with super high dosages for long time if it's thiamine hcl (water soluble form), fat soluble form is not recommended in high doses. Don't know much about theanine dosage, but it's recommended to take 200mg for people who get jitters from coffee and I even saw sleep suplement formula which contains 1gram of theanine, but start at 100-200mg and increase dosages if needed. Start with smaller dosages and also do your own research.