Management of Hypomagnesaemia

N.B. Use of magnesium for other indications e.g. eclampsia is outside the scope of this guideline. The reference range for serum magnesium is 0.7-1mmol/L. Serum concentrations should be used in conjunction with presenting signs and symptoms to diagnose hypomagnesaemia (see notes below).

Adults with normal renal function

Magnesium levels should be monitored, and the dose adjusted as necessary. See flowchart below.

Adults with renal impairment

In patients with renal impairment reduced urinary magnesium excretion puts the patient at risk of hypermagnesaemia. See flowchart below for dosing guidance.

Additional information

• Magnesium is mainly an intracellular ion, so serum concentrations are not an exact measurement of total body stores.
• Magnesium depletion is often associated with other electrolyte abnormalities - reduced K⁺, Ca²⁺, PO₄^3- or Na⁺ levels may co-exist with a low Mg²⁺.
• Possible symptoms include agitation, confusion, convulsions, weakness, tremors, ECG changes, nausea and vomiting.
• Establish and correct cause if possible.

• Flowchart Management of hypomagnesaemia

N.B. Doses shown in the flowchart are suggested starting doses. Further advice is available from the Biochemistry Department.

Guideline reviewed: February 2023

Page last updated: March 2023