The magnesium in most multivitamins is magnesium stearate.

This is an INsoluble form that is used as a filler to make the total
product move thru the pressing machines without sticking.

It is not absorbed and provides no magnesium to your body.

This is my magnesium thread: it explains how much and what type to choose. It also has food sources so you can decide to improve diet so that more magnesium will be available to you.

Magnesium in mixture products like cal/mag...is often magnesium oxide. This type is very inexpensive and historically was always provided. But recent studies have shown that it is not absorbed much either. So now it is mostly a laxative and is
found in Phillips tablets today (as advertised on TV).

So read labels carefully before you take a magnesium product so you will choose one that works.

http://neurotalk.psychcentral.com/thread1138.html

The world of supplements is very complicated. Not all are equal in quality, by any means!

Magnesium at night is a good idea, as it is relaxing. Many of us on
the PN forum use a topical lotion for it, and rub it on at night. It will
calm you down and facilitate sleep. Some people are sensitive to the laxative actions of all magnesium products so the topical avoids that side effect.

You can also bathe in epsom salts in a bath tub. This is very relaxing and some magnesium does cross the skin and get into your blood steam that way. Do NOT use hot water... lukewarm only. About 6 ounces to a bath tub and soak at least a 1/2 hr.