Routine Magnesium Supplementation doesn't lower rates of tachyarrhythmias, hypotension or death in critically ill patients: JAMA
According to a new study published in JAMA Internal Medicine routine magnesium supplementation does not result in lower rates of tachyarrhythmias, hypotension, or death in critically ill patients with magnesium levels near current treatment cutoffs. Magnesium is commonly administered to intensive care unit (ICU) patients with serum levels below institutional reference ranges, primarily to prevent arrhythmias, such as atrial fibrillation. The study was conducted by Robert G. and colleagues.
Hypomagnesemia is common in critically ill patients and until recently magnesium supplementation was considered to be a low-risk intervention with potential cardiovascular benefit. Many institutions commonly give magnesium when serum levels drop below predefined cutoffs, which are usually between 1.6 to 2.0 mg/dL. Despite this practice, it is unknown if this supplementation actually reduces clinically important outcomes such as tachyarrhythmia, hypotension, and mortality.
In this single-group, nonrandomized clinical trial, ICU patients undergoing serum magnesium testing were studied in 93 ICUs in the United States and Europe from 2003 to 2022. The analysis used a fuzzy regression discontinuity design, comparing patients just below and just above institutional eligibility cutoffs for magnesium supplementation. This quasi-experimental method enables more credible causal inference than traditional observational studies. Several thresholds of treatment were studied in active clinical use, ranging from a lower threshold of 1.6 mg/dL to an upper threshold of 2.0 mg/dL.
Data analysis was performed from August to October 2025.The analyses included 478 901 twenty-four–hour treatment windows derived from 171 727 ICU admissions. Of the patients admitted, 72 767 (42.4%) were female and 98 960 (57.6%) male, with a mean (SD) age of 63 (16) years. Of interest was the exposure to magnesium supplementation after serum magnesium testing.
Key Findings
• Magnesium supplementation was not associated with a reduced risk of tachyarrhythmia, with a risk difference of 0.1% (95% CI, −4.2 to 6.9) comparing patients just below versus just above treatment thresholds.
• This lack of association was consistent across all cutoff levels from 1.6 mg/dL to 2.0 mg/dL.
• Similarly, magnesium supplementation showed no meaningful effect on hypotension, with a risk difference of 1.2% (95% CI, −0.9 to 17.7), or on mortality, with a risk difference of 1.4% (95% CI, −0.6 to 5.3).
• These findings suggest no measurable clinical benefit from routine magnesium replacement at commonly used thresholds.
In this large, quasi-experimental study of critically ill patients, routine magnesium supplementation at currently used treatment thresholds was not associated with reduced tachyarrhythmia, hypotension, or mortality among patients with serum magnesium values close to those cutoffs. These findings challenge the practice of routine supplementation and suggest a revisiting of the thresholds for and indications of magnesium treatment may be required.
Reference:
Goulden R, Abrahamowicz M, Strumpf E, Tamblyn R. Magnesium Supplementation and Tachyarrhythmias: A Nonrandomized Clinical Trial . JAMA Intern Med. Published online December 08, 2025. doi:10.1001/jamainternmed.2025.6572
