Magnesium, Serum
What This Test Measures
Electrolyte important for nerve, muscle, and cardiac function; commonly deficient.
Preparation
IMPORTANT: The thyroid and chronic illness communities widely note that serum magnesium is a POOR marker — it reflects less than 1% of body stores. A 'normal' serum magnesium does NOT rule out deficiency. By the time serum magnesium drops below range, deficiency is severe. Request RBC magnesium instead for a meaningful assessment. Symptoms of low magnesium (muscle cramps, fasciculations, poor sleep, migraine, anxiety, heart palpitations) frequently persist even with normal serum levels. The functional medicine community strongly prefers RBC magnesium for assessing true status. 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
Serum magnesium doesn't reflect intracellular status; RBC magnesium more informative
ICD-10 Codes
Common diagnosis codes associated with this test. Codes are assigned by your provider.
Self-Pay Pricing
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Uses Labcorp network; known for supplement company; competitive lab test pricing
Uses Quest Diagnostics network; generally lowest DTC prices; not available in NY, NJ, RI
Uses both Quest and Labcorp networks; competitive pricing; broad test selection
Uses Quest and Labcorp; strong panel bundling; results in 1-3 days
Uses Quest and Labcorp networks; offers both individual tests and discounted panels
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.