Serum Magnesium Testing

A serum magnesium test can read as normal even when the body is substantially depleted at the cellular level. Subclinical magnesium deficiency does not appear on standard lab work yet produces real, measurable symptoms. Standard blood panels are an unreliable tool for detecting magnesium deficiency because only a tiny fraction of total body magnesium circulates in plasma. The article says standard blood magnesium tests are poor indicators of intracellular magnesium deficiency. The article says RBC magnesium testing is limited because red blood cells lack mitochondria, where much magnesium is bound to ATP. The article says IV magnesium loading with 24-hour urinary excretion and tissue biopsy are impractical despite being stronger tests. The article claims serum magnesium can appear normal while tissues are depleted because the body defends plasma magnesium levels.