i'm basically relying on 2 magnesium oxide 375mg tablets a day, 1 in the morning and 1 at night. i'm just hoping it won't cause any other problems in the long run.
is it safe?

I would like to know too, I take magnesium citrate 160mg for three times a day (480mg per day), more then a month now but these days, I got rash all over my body. Please let me know for the safe dose, thanks.

Magnesium is actually quite poorly absorbed by the gut. People who take magnesium aspartate (magmin) for magnesium deficiency typically take up to 1g twice to three times daily. I have never seen any of these patients end up with high serum magnesium levels (most struggle to reach normal). Partly because diarrhoea limits the maximum dose for magnesium replacement. I'm not sure of the equilivant elemental magnesium dose, but it is probably available online.

If you have normal kidney function, excess magnesium is cleared from the body quite easily. I have seen people with serum magnesium levels nearly 3 times the upper limit of normal (after exuberant IV replacement in an ICU patient) without ill effects. It was cleared by the kidneys over the next day or so.

I'm not familiar with magnesium dosing for constipation, but I'm aware some people use epsom salts. Dosing guidelines are available elsewhere. But I thought I'd chip in what I know if magnesium safety! Most doctors would recommend movicol, lactulose or maybe dulcolax drops.