What does the Red Blood Cell Magnesium test measure?

Why is Red Blood Cell Magnesium measured?

RBC magnesium is used as a more sensitive index of intracellular magnesium status than serum magnesium, particularly when functional deficiency is suspected despite a normal serum value. It is favoured in functional and integrative practice for detecting chronic depletion that serum testing may miss. Its limitations are a lack of standardised reference intervals and less outcome-based validation than serum magnesium, so it is interpreted as a supportive rather than definitive measure of magnesium status.

Reference ranges

Standard reference

4.2–6.8 mg/dL (1.73–2.80 mmol/L) # REVIEWER FLAG: RBC magnesium reference intervals vary considerably by laboratory and method — reviewer to confirm against Access Medical Laboratories' assay-specific range.

Functional medicine optimal

Upper half of the reference range is often targeted as functionally optimal # REVIEWER FLAG: Functional 'optimal' RBC magnesium target is not standardised and method-dependent — reviewer to confirm against IFM or equivalent source.

Units

mg/dL, mmol/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.