Magnesium (Red Blood Cell / Intracellular)
Red blood cell magnesium measures the magnesium held inside your red blood cells rather than in the surrounding serum. It aims to reflect your body's magnesium status more closely than a standard serum test.
Magnesium supports hundreds of processes, including muscle and nerve function, blood sugar handling, and energy production. Because most magnesium sits inside cells and bone, a serum test can look normal even when body stores are low, so RBC magnesium is sometimes used for a fuller picture. Levels can be affected by diet, gut conditions, and certain medications.
A high RBC magnesium is uncommon in people with healthy kidneys and may reflect supplementation or reduced kidney clearance. Because the kidneys normally remove excess magnesium, a high value can prompt a look at kidney function and supplement use. It is interpreted alongside your other results.
A low RBC magnesium suggests your stores may be depleted, which can affect muscles, nerves, and other magnesium-dependent processes. It may reflect low intake, losses, or absorption problems.
Labs provide a reference range, though there is ongoing discussion about how best to assess magnesium status. A clinician can help you interpret your result and consider your symptoms.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.