Serum vs intracellular

Serum magnesium represents up to 1.0% of the magnesium in the body and rbc (red blood cell) magnesium represents about 40%. I think of the intracellular rbc magnesium test (RBCMg test) as a long term evaluation of magnesium much like the A1C test for glucose. My doctors didn't know about the RBCMg test until I requested it.