What Is an RBC Magnesium Test?
RBC magnesium measures magnesium inside red blood cells, reflecting total body stores better than serum magnesium.
Why RBC Magnesium Is Better
- Serum Mg only reflects 1% of body magnesium
- 99% is stored in bones and cells
- Serum may be normal despite total depletion
- RBC Mg reflects cellular magnesium over weeks
Normal Range
- 4.0–6.0 mg/dL (varies by lab)
Who Should Consider RBC Mg?
- Chronic muscle cramps
- Cardiac arrhythmias
- Fibromyalgia
- Migraines
- Long-term PPI use
- Alcohol use
Source: NLM MedlinePlus, AACC.
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