ive been having similar suspicions about magnesium absorption too actually. I have been orally taking 600mg daily of magnesium citrate for over a month now and I was expecting it to have a much stronger effect on my body, in regards to it often being given as a laxative, but theres been zero change on that side of things. This is making me suspect that my body isnt actually absorbing it that efficiently. Maybe I should try and switch over to topical as well now...