Low magnesium associated with higher mortality

Emergency patients with low magnesium had higher 30-day mortality.
*Retrospective propensity-matched cohort study; Level 2 (OCEBM).

Citation

Singer DD, Zhang Z, Peacock WF, Singer AJ. Hypomagnesemia and 30-day mortality in the emergency department: A large-scale propensity-matched analysis. American Journal of Emergency Medicine. 2026;110:349-354.

Background

Low magnesium is common in acutely ill patients, but its importance in emergency department patients is uncertain. This study examined how often it occurred and whether it was linked to short-term death.

Patients

Adults aged 18 years or older with an emergency department visit in 2025 and a measured magnesium level. Patients younger than 18 were excluded.

Intervention

Low magnesium, defined as 1.6 mg/dL or lower.

Control

Normal magnesium, defined as 1.7 to 2.2 mg/dL.

Outcome

Primary outcome: death within 30 days. Secondary outcomes: death within 7 days and dangerous heart rhythm problems.

Follow-up Period

7 and 30 days after the index emergency department visit.

Results

Among 1,246,550 eligible patients, 164,663 had low magnesium. After matching, low magnesium remained associated with worse outcomes.

Outcome Low magnesium Normal magnesium Effect
30-day death (primary) 3.24% 1.91% OR 1.72 (95% CI 1.67 to 1.78); number needed to harm 75
7-day death 1.23% 0.76% OR 1.64 (95% CI 1.55 to 1.72)
30-day dangerous rhythm problem 1.58% 1.12% OR 1.32 (95% CI 1.27 to 1.39)

OR: odds ratio; CI: confidence interval; OCEBM: Oxford Centre for Evidence-Based Medicine.

More severe magnesium deficiency showed higher mortality and rhythm-problem rates. The normal-magnesium group was a comparison group, not a treatment control.

Limitations

This observational study cannot prove that low magnesium caused death or that replacement improves survival. Only patients who had magnesium measured were included. Unmeasured illness severity, diet, medications, and care outside participating systems may have affected results.

Funding

No study funding reported; senior author’s journal role was managed.

Clinical Application

Consider magnesium testing in higher-risk emergency patients; do not assume replacement lowers mortality without prospective trials.