What Is RBC Magnesium?
Magnesium is involved in over 300 enzymatic reactions. About 99% is stored inside cells and in bone. Only 1% circulates in blood.
The standard serum magnesium test measures the 1% in blood, which stays normal even when intracellular stores are depleted. RBC magnesium measures magnesium inside red blood cells — a more accurate reflection of actual tissue status.
Why Magnesium Deficiency Is Common
An estimated 45–60% of North Americans don't consume adequate dietary magnesium due to soil depletion, food processing, gastrointestinal losses, and increased excretion from caffeine, alcohol, and stress.
What Magnesium Deficiency Causes
- Muscle cramps and spasms
- Sleep difficulties — magnesium is required for GABA activity
- Anxiety and mood
- Headaches and migraines
- Fatigue — required for ATP production
- Cardiovascular effects — associated with elevated blood pressure and arrhythmias
- Insulin resistance — required for insulin receptor signaling
RBC Magnesium Reference Ranges
Below 1.65 mmol/L: Deficient. 1.65–2.20: Normal. Above 2.20: High.
How to Optimize Magnesium
- Dietary sources — dark leafy greens, pumpkin seeds, almonds, dark chocolate
- Supplementation — magnesium glycinate and malate have the best absorption
- Addressing losses — reducing caffeine and alcohol, managing stress
Is Magnesium Tested in a Standard Physical?
RBC magnesium is almost never ordered in routine care. Stem Health tests RBC magnesium in every Core and Horizon Assessment.
