Magnesium Supplementation and Tachyarrhythmias: A Nonrandomized Clinical Trial
Abstract
Importance
Magnesium supplementation is regularly given to acutely ill patients with serum levels below the standard reference range, primarily for the prevention of tachyarrhythmias, such as atrial fibrillation. The evidence for this practice and the specific treatment thresholds used is limited. Conventional observational studies of this question are at risk of confounding by indication and other biases.
Objective
To determine whether giving magnesium supplementation to patients with hypomagnesemia, as defined by a given institution's usual treatment cutoff, reduces adverse clinical outcome using a quasi-experimental study design that plausibly allows for causal inference.
Design, Setting, and Participants
This nonrandomized clinical trial of intensive care unit (ICU) patients undergoing serum magnesium testing was conducted in 93 ICUs across the US and Europe between 2003 and 2022. A fuzzy regression discontinuity design was used, in which individuals just either side of the eligibility cutoff for magnesium supplementation were compared with regard to the study outcomes. This comparison was performed across a range of treatment cutoffs in current use, ranging from 1.6 mg/dL to 2.0 mg/dL. Data were analyzed from August to October 2025.
Exposures
Magnesium supplementation.
Main Outcomes and Measures
The primary outcome was ventricular or supraventricular tachyarrhythmia in the 24 hours after magnesium testing. Secondary outcomes were the occurrence of hypotension or death.…
How strong is the evidence?
Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design. Reported size: 72 participants or records.
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