[2] Treatment when levels are very high include calcium chloride, intravenous normal saline with furosemide, and hemodialysis.

[8] Magnesium acts as a physiologic calcium blocker, which results in abnormalities of the electrical conduction system of the heart.

[citation needed] Consequences related to serum concentration:[9]: 281 At magnesium levels about 4.5 mEq/L the stretch reflex is lost and with over 6.5 mEq/L respiratory failure may be observed.

[10] As per Lu and Nightingale,[11] serum magnesium concentrations associated with maternal toxicity (also neonate depression, hypotonia and low Apgar scores) are:[citation needed] Severe hypermagnesemia (levels greater than 12 mg/dL) can lead to cardiovascular complications (hypotension and arrhythmias) and neurological disorder (confusion and lethargy).

[1] People with normal kidney function (glomerular filtration rate (GFR) over 60 ml/min) and mild asymptomatic hypermagnesemia require no treatment except for the removal of all sources of exogenous magnesium.

As a consequence, the treatment of this electrolyte disorder can frequently require intensive care unit (ICU) admission.

For instance, during the management of eclampsia, the magnesium infusion is stopped if urine output drops to less than 80 mL (in 4 hours), deep tendon reflexes are absent, or the respiratory rate is below 12 breaths/minute.

Furthermore, epidemiological data suggest that there is a significant prevalence of high levels of serum magnesium in selected healthy populations.

High magnesium concentrations were typical in people with cardiovascular disease, and 2.3 mg/dL or higher values were associated with worse hospital mortality.