Magnesium, RBC
What This Test Measures
Red blood cell magnesium; better indicator of intracellular magnesium status than serum magnesium.
Preparation
PREP: No special fasting required, but the functional medicine community recommends not taking magnesium supplements the morning of the test for consistency. RBC magnesium is the preferred test — serum magnesium reflects less than 1% of body stores and can be 'normal' even with significant deficiency. The functional medicine community targets mid-range or higher on RBC magnesium. Symptoms of deficiency (cramps, poor sleep, anxiety, palpitations, migraines) frequently persist even with normal serum levels. If your provider only orders serum magnesium, request RBC magnesium instead. These notes reflect common practices in thyroid/functional medicine communities.
Reflects common practices in thyroid, BHRT, and functional medicine communities. This may differ from standard clinical guidelines. Not medical advice — always discuss with your provider.
General guidelines only. Requirements vary by lab and individual. Confirm with your provider before adjusting any medications.
Turnaround Time
Varies by lab
Clinical Notes
Preferred functional magnesium marker; reflects intracellular stores more accurately
ICD-10 Codes
Common diagnosis codes associated with this test. Codes are assigned by your provider.
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Lab Codes
Proprietary codes used by each lab for this test.
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For informational purposes only
This page is for educational and research purposes only and does not constitute medical advice, diagnosis, or treatment recommendations. ICD-10 and CPT codes are assigned by your healthcare provider. Always consult a qualified healthcare provider before ordering any lab test or making decisions about your health.