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