It is impossible to give you the magnesium dose that will work for you...why I wrote "to tolerance" in intro post. That means try magnesium (there are three kinds, each absorb/have laxative effect differently) and increase dose until it works..or works too much and then back off. Magnesium oxide has more a laxative effect than citrate and each brand will work differently for you than me.
Most are sold in doses of 200 or 400mg, buy the 200 and you can add pills until effective. Hope that helps,