RBC Magnesium
Magnesium measured inside red blood cells, sometimes used to estimate body magnesium stores.
| Typical reference range | 4–6.4 mg/dL |
| Commonly cited optimal range | above 5 mg/dL |
Ranges vary by laboratory, method, age and sex: always use the range printed on your own report. Why labs differ.
What it measures
This test measures the magnesium content of red cells, which is about three times higher than in serum and changes more slowly.
Why it matters
Because serum magnesium is tightly regulated, RBC magnesium is sometimes used to detect deficiency that serum tests miss, though its superiority is not firmly established.
What a high result can mean
High values are uncommon and may reflect supplementation or kidney impairment.
What a low result can mean
Low values suggest depleted magnesium stores from low intake, alcohol use, diuretics, proton pump inhibitors, GI losses or diabetes.
What affects the result
Reference ranges vary considerably between labs. Interpret with serum magnesium, potassium and calcium.
Units and conversion
Usually reported in mg/dL.
- From mmol/L: multiply by 2.431 to get mg/dL
Also called on lab reports
Magnesium, RBC, Red Blood Cell Magnesium, Magnesium, Red Blood Cell, Erythrocyte Magnesium
Related tests: Vitamins & Nutrients
This page is educational and does not replace advice from a healthcare professional.