Magnesium, Red Blood Cell (RBC) Test

This test measures the amount of magnesium inside your red blood cells (erythrocytes), rather than the magnesium circulating in your bloodstream. Because most of the body's magnesium is stored inside cells, a red blood cell magnesium measurement gives a more accurate picture of your true magnesium status than a standard serum magnesium test. It is particularly useful for people whose serum magnesium appears normal but who have symptoms or risk factors suggesting a hidden deficiency.

Magnesium is involved in over 300 enzymatic reactions in the body, including energy production, muscle and nerve function, blood pressure regulation, blood glucose control, and bone health. Low intracellular magnesium has been linked to muscle cramps, fatigue, palpitations, poor sleep, headaches, and increased cardiovascular and metabolic risk. This test is suitable for anyone with persistent symptoms despite normal serum magnesium, those taking diuretics or proton pump inhibitors, people with poorly controlled diabetes, alcohol dependence, gastrointestinal disorders causing malabsorption, or those simply wanting a deeper insight into their mineral status.

Biomarkers
- Red blood cell magnesium (RBC Mg): measures the concentration of magnesium within red blood cells, reflecting body stores more reliably than serum magnesium.

Why it matters
A normal serum magnesium result does not rule out deficiency, because the body tightly regulates blood levels at the expense of cellular stores. Measuring magnesium inside red blood cells can uncover a hidden shortfall that may explain persistent symptoms and allows you and your clinician to address the root cause with appropriate dietary and supplementation strategies.

Vitamins & Minerals
- Red blood cell magnesium (RBC Mg)

No special preparation required.

For blood tests, we recommend drinking plenty of water beforehand to ensure smooth sample collection. If you are taking any regular medication, continue to do so unless advised otherwise by your doctor.