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Marker · Ranges for learning, not a diagnosis

RBC magnesium

Also called red-cell magnesium, erythrocyte magnesium.

Magnesium measured inside red blood cells, not in the liquid part of blood (serum). Serum holds about 0.3 percent of the body's magnesium. That is why a normal serum number can hide low stores in the body.

Read this first

  • Coach, not doctor. Aaron Cuha is a coach, not a doctor. No medical credential is claimed for him, or for these pages. A number on a blood test is something to talk over with a doctor, not something to diagnose yourself with. Nothing here is a prescription, a plan to follow, or a reason to start or stop a medicine. Educational use only. This database summarizes published research and is not medical advice. Where a dose appears it is a record of what a trial or clinic ran, or what people describe doing, with its source attached. Nothing here is a recommendation for personal use.
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  • Three kinds of lab page, kept apart. /bloodwork is blood tests for people. /testing and /prices/labs are lab tests on peptide vials. /supplements/quality is what is in the bottle.

Why a longevity audience asks

The owner's basic list uses red blood cell magnesium, not serum, as the number to watch. Magnesium pills lower blood pressure a little, and that is real. Sleep and brain claims have much less behind them than the ads say.

How a coach reads it

There is no single cut-off this site will print as a diagnosis. Ask the lab how it runs the red blood cell test and what its normal range is. Treat serum magnesium as background, not reassurance. The owner takes magnesium glycinate on his basic list and still wants the red blood cell number. This is not a diagnosis.

Units on this page: mg/dL, mmol/L

When it is low

May mean you take in too little, lose too much, or your blood level is being held steady while your body stores run low. Cramps do not prove a low number, and a low number does not explain cramps.

When it is high

High magnesium, especially with weak kidneys, needs a doctor. Do not add more magnesium to chase a feeling unless a doctor has cleared your kidneys for it.

Easy ways to misread it

  • Serum magnesium is the test most panels run, and it is the one most likely to look fine.
  • Labels often give the weight of the whole compound, not how much actual magnesium is in it.
  • Kidney disease changes whether the bottle is safe. A doctor has to clear that.

What to ask your doctor

Ask for red blood cell (RBC) magnesium, not serum alone. Mention kidney disease, water pills, a GLP-1 weight-loss drug, or low-carb eating if any of those apply.

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Sources on this page