Magnesium (RBC)
Also reported as: Red blood cell magnesium · Erythrocyte magnesium
Magnesium inside red blood cells, which reflects tissue stores far better than the serum magnesium usually included on a routine panel.
For RBC magnesium. Serum magnesium (1.7–2.2 mg/dL) is a different test and a much weaker one.
Upper half of the reference range is the usual target, as symptoms of insufficiency are reported well within the lower half.
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Where the thresholds sit
| Band | Range (mg/dL) | Note |
|---|---|---|
| Low | < 4.2 | — |
| Below optimal | 4.2–5.6 | — |
| Optimal | 5.6–6.8 | — |
| High | > 6.8 | Uncommon outside kidney impairment or supplement excess. |
Why it matters
Magnesium is a cofactor in hundreds of enzymatic reactions including ATP handling, and intake sits below recommended levels for a large share of adults. The reason to ask specifically for the RBC test is that serum magnesium is tightly defended — the body will strip bone stores to hold it steady — so a normal serum result tells you very little about whether you have enough.
What raises it
- Supplementation
- Kidney impairment reducing excretion
What lowers it
- Diets low in leafy greens, nuts and legumes
- Proton pump inhibitors, over months to years
- Diuretics
- Alcohol
- Poorly controlled diabetes
- Heavy sweating
How to move it
- 1Ask for RBC magnesium specifically. A normal serum magnesium is close to meaningless for assessing status.
- 2Food first: pumpkin seeds, almonds, spinach, black beans and dark chocolate are the densest sources.
- 3If supplementing, glycinate and malate are well absorbed and gentle. Oxide is cheap, poorly absorbed and mostly a laxative.
- 4Take it in the evening — many people find it helps sleep.
- 5Long-term PPI users should have this checked; depletion is well documented and easily missed.
What moves this marker
Interventions on this site with evidence behind them for this specific marker. None of them replaces working out why yours is where it is.
What makes a single reading misleading
- Most panels report serum magnesium by default, which is not the same test.
- Even RBC magnesium is an imperfect proxy for the intracellular magnesium that matters most.
- People with impaired kidney function should not supplement without medical advice.
Sources
Read next
Educational only. Reference ranges are not diagnostic thresholds and this page cannot account for your medical history, medication or symptoms. Discuss any result that concerns you with a qualified clinician. See our medical disclaimer.