Treatment of Hypomagnesaemia with Serum Magnesium Below 0.4 mmol/L, or 0.40–0.49 mmol/L with Symptoms
This protocol covers the inpatient management of hypomagnesaemia in two specific presentations: a serum magnesium level below 0.4 mmol/L, or a level of 0.40 to 0.49 mmol/L in a patient who is symptomatic. Both scenarios require admission to hospital.
Clinical Scenario
Serum magnesium <0.4 mmol/L — or serum magnesium 0.40 to 0.49 mmol/L with symptoms of hypomagnesaemia. Hospital admission is required in either case.
Treatment Approach
Intravenous magnesium replacement is indicated in this acute inpatient setting. The approach is structured across the first 24 hours and subsequent days, with dose adjustments guided by renal function and ongoing serum magnesium monitoring. The complete phased regimen is available in the full protocol.
Treatment Goal
Normalisation of serum magnesium to within the reference range (0.70–1.0 mmol/L), confirmed by daily monitoring.
References
- <0.4 IV Magnesium Admission to hospital required.
- 0.40 to 0.49 and symptomatic IV Magnesium Admission to hospital required.
- Dilute 10mL of 50% solution (5g; 20mmol) in at least 250mL sodium chloride 0.9% or glucose 5%, and administer as an intravenous infusion over 3 hours.
- This dose may be repeated once during the first 24 hours, guided by serum magnesium levels.
- Dilute up to 12mL of 50% solution (6g; 24mmol) in at least 250mL sodium chloride 0.9% or glucose 5%, and administer as an intravenous infusion over 6 hours.
- Repeat dose daily, with daily monitoring until magnesium is normal. A total of 5 days therapy may be required.
- In patients with renal impairment, it has been suggested to give 25 to 50% of the normal dose.