Cox, I M, Campbell, M J, Dowson, D · Lancet (London, England) · 1991 · DOI
This study tested whether people with ME/CFS have lower magnesium levels in their red blood cells and whether magnesium injections could help them feel better. Researchers compared 20 ME/CFS patients to 20 healthy people and found the patients did have lower magnesium. When 15 ME/CFS patients received weekly magnesium injections for 6 weeks, 12 reported feeling better with more energy and less pain, compared to only 3 out of 17 patients who received a placebo injection.
This study provides early evidence that magnesium deficiency may be involved in ME/CFS pathophysiology and suggests a potentially safe, inexpensive therapeutic intervention. The significant treatment effect (80% vs. 18% improvement) and documented correction of cellular magnesium in treated patients make this relevant for exploring metabolic and biomarker-driven approaches to ME/CFS management.
This study does not prove that magnesium deficiency causes ME/CFS, only that an association exists in this sample. The subjective nature of primary outcome measures (patient-reported wellbeing) without objective biomarkers of fatigue or dysfunction limits causal claims. The small sample size and single-site recruitment prevent generalization to all ME/CFS patients, and the mechanism by which magnesium improves symptoms remains unexplained.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Cox, I M, Campbell, M J, & Dowson, D (1991). Red blood cell magnesium and chronic fatigue syndrome.. Lancet (London, England). https://doi.org/10.1016/0140-6736(91)91371-z
BibTeX
@article{mecfsatlas-cox-1991-red-blood,
author = {Cox, I M and Campbell, M J and Dowson, D},
title = {Red blood cell magnesium and chronic fatigue syndrome.},
journal = {Lancet (London, England)},
year = {1991},
doi = {10.1016/0140-6736(91)91371-z},
note = {PubMed: 1672392},
url = {https://www.mecfsatlas.com/evidence/cox-1991-red-blood},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-28. https://www.mecfsatlas.com/evidence/cox-1991-red-blood
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