Why Serum Magnesium Fails: A Narrative Review of Magnesium Biochemistry, Compartmental Exchange, and Endpoint Selection for Supplementation Trials.
Level 5 - mechanism / opinion, no new human data
Narrative review and mechanism-based reasoning with no primary human data.
PubMed 42647115 · doi:10.1080/27697061.2026.2719468
What was done
This narrative review analyzed magnesium biochemistry, compartmental distribution kinetics, and biomarker endpoints used in oral supplementation trials. The authors evaluated serum, erythrocyte, ionized, urinary, and loading-test measurements across five clinical domains (essential hypertension, insulin resistance/type 2 diabetes, insomnia, muscle cramping, and migraine prophylaxis) to assess endpoint adequacy against physiological timescales.
What was found
No new primary data were collected; published biological variation metrics were synthesized: - Serum magnesium accounts for <1% of total body magnesium, with a reference change value of approximately 12%. - Erythrocyte magnesium integrates intracellular exposure over approximately 120 days, with a critical difference/reference change value of approximately 22%. - Because oral supplementation produces biochemical changes comparable to or smaller than these reference change values, trials relying on serum levels are methodologically underpowered to detect tissue repletion, explaining null biochemical findings alongside positive clinical outcomes.
Why it matters
This review explains why normal serum magnesium fails to rule out tissue depletion and proposes erythrocyte magnesium as a more physiologically sound group-level endpoint for supplementation trials lasting 3 months or longer.
Limits
As a narrative review, it lacks a systematic search protocol, formal risk of bias evaluation, and meta-analytic pooling. The proposed kinetic model and biomarker hierarchies rely on synthesis of secondary literature rather than new primary experimental data.
Cited by
- supports Magnesium is required as a cofactor for 300 to 600 enzymatic reactions in the human body.
- supports Serum magnesium tests cannot accurately detect cellular or tissue magnesium depletion unless the deficiency is severe.