ive been googling a lot about the best magnesium test. cause as you may already know serum is a poor way to measure it. from pubmed: Deranged magnesium concentrations in serum and cardiovascular structures have been implicated in the pathophysiology of hypertension, ischemic heart disease, arrhythmias, and sudden death. This study was conducted to determine the status and interrelation of serum and tissue concentrations of magnesium in patients with congestive heart failure, a clinical setting purportedly predisposed to the development of depleted levels of this cation. Magnesium concentrations of serum, circulating mononuclear cells, skeletal muscle, and myocardium were measured in 23 patients with heart failure on standard therapy. Two patients were hypomagnesemic (less than 1.6 meq/l). Poor or no correlations were found between serum and tissue magnesium concentrations and among the magnesium concentrations of the three tissues studied. and some other websites: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1855626/ http://ckj.oxfordjournals.org/content/5/Suppl_1/i3.full http://www.nytimes.com/2004/05/18/h...ral-you-need-and-probably-didn-t-know-it.html http://circ.ahajournals.org/content/80/3/573 http://www.mgwater.com/laboratory_test.shtml anyway some of them mention that ionized is the better method than serum, rbc and mononuclear blood cell/white blood cell is better than rbc for cardiac. my questions are. does anyone knows if theres a lab which does ionized mag test, mbc/wbc mag test for international client? (i only can find spectracell but they cant test per item but 34) i also came accros exatest which stated it can measure intracellular mag, cal, pot, etc and their research seems promising but im not sure cause not much to 'see' on their website also lack info from other people, the cost, etc are they really credible?