In general the mid range of magnesium is
Not representative of tissue levels.
The very low range and very very high
Are used diagnostically for serious often
emergency situations.

Daily use of diuretics and chemotherapy
Can put one into a serious low area that can
impact the heart. Very high levels can be
Found in people abusing Fleet enemas and
Fleet laxatives but the latter were changed
For testing preps because of this.

Doctors use very high levels in treatment infusions
IV and those can be problematic
For patients with kidney problems.
Oral use usually causes diarrhea as a warning
To lower dosing but no such warning comes
With IV admin where doses may approach
6 grams IV.