like Rita, I've had good some experience with Mg. But which to take?
From my reading and experience, these points might be helpful to some:
the Mg Oxide usually sold in stores is cheap but said to be absorbed only ~10% or less
Mg Glycinate is absorbed well and also said to be non-laxative. I'd say that's only partially true. I usually don't mind taking things that taste terrible, but after months of this, it was too much.
Mg Maleate is absorbed well, and has an almost pleasant mildly sour taste.
Mg Citrate is said to absorb well, too.
It's hard to get Mg from food, there isn't that much of it around (nuts, etc). That makes me think of the "aquatic ape" theory, and so our ancestors maybe absorbed it through the skin from ocean water. Sounds odd at first, but I've come to believe it.
The Mg "oil" (which is really a viscous water-based form) is also sold in a spray, to be absorbed through the skin.
Epsom salts are Mg Sulfate, which can also get in through the skin. E.g., bath or footbath. In anything transdermal, there should be no laxative effect.
But taking Mg Sulfate orally (as in Milk of Magnesia) would have the max laxative effect, and minimum amount getting into the blood.
probably you take all minerals with food, so as to get the stomach acid for absorption. But if a person has low thyroid, then they don't produce so much acid. You can then maybe use lemon juice or vinegar.
Ways to lose Mg, by excretion in urine:
eat sugar
drink alcohol
have stress
take a diuretic
Mg is called the relaxing mineral