What is the treatment for hypomagnesemia (low magnesium levels)?

From the Guidelines

Treatment of hypomagnesemia should start with oral magnesium oxide supplementation, given as gelatine capsules of 4 mmol magnesium oxide (160 mg of MgO) to a total of 12–24 mmol daily, as it contains more elemental magnesium than other salts and is soluble in dilute acid. This approach is based on the guidelines for management of patients with a short bowel, which emphasize the importance of correcting dehydration and secondary hyperaldosteronism as the first step in treating hypomagnesemia 1.

Key Considerations

• Oral magnesium supplements are preferred, but if they do not normalize magnesium levels, oral 1-alpha hydroxy-cholecalciferol may be added in a gradually increasing dose to improve magnesium balance, with regular monitoring of serum calcium to avoid hypercalcaemia 1.
• Intravenous or subcutaneous infusion of magnesium may be necessary in severe cases or when oral supplements are not effective, usually with saline 1.
• It is essential to address the underlying cause of magnesium deficiency, whether it's medication-induced, malabsorption, or other conditions, to prevent recurrence and ensure effective treatment.

Monitoring and Adjunctive Therapy

• Concurrent potassium and calcium levels should be monitored, as hypomagnesemia often occurs alongside deficiencies in these electrolytes 1.
• The treatment plan should be adjusted based on the severity of hypomagnesemia, with more aggressive replacement strategies used for severe cases or symptomatic patients.
• Other measures, such as reducing oral hypotonic fluids, giving glucose/saline solution to sip, and adding sodium chloride to liquid feeds, may be necessary to manage related conditions, such as high output enterocutaneous fistula or ileostomy diarrhea 1.

From the FDA Drug Label

In the treatment of mild magnesium deficiency, the usual adult dose is 1 g, equivalent to 8. 12 mEq of magnesium (2 mL of the 50% solution) injected IM every six hours for four doses (equivalent to a total of 32.5 mEq of magnesium per 24 hours). For severe hypomagnesemia, as much as 250 mg (approximately 2 mEq) per kg of body weight (0. 5 mL of the 50% solution) may be given IM within a period of four hours if necessary. Alternatively, 5 g (approximately 40 mEq) can be added to one liter of 5% Dextrose Injection, USP or 0. 9% Sodium Chloride Injection, USP for slow IV infusion over a three-hour period.

The treatment of hypo magnesia (magnesium deficiency) involves administering magnesium sulfate.

• For mild magnesium deficiency, the usual adult dose is 1 g (8.12 mEq of magnesium) injected IM every six hours for four doses.
• For severe hypomagnesemia, the dose can be as much as 250 mg (approximately 2 mEq) per kg of body weight given IM within a period of four hours if necessary, or 5 g (approximately 40 mEq) added to one liter of 5% Dextrose Injection, USP or 0.9% Sodium Chloride Injection, USP for slow IV infusion over a three-hour period 2.

From the Research

Treatment of Hypomagnesemia

• Hypomagnesemia is defined as a serum magnesium level less than 1.8 mg/dL (< 0.74 mmol/L) 3
• Asymptomatic patients should be treated with oral magnesium supplements, while parenteral magnesium should be reserved for symptomatic patients with severe magnesium deficiency (< 1.2 mg/dL) 3, 4
• Establishment of adequate renal function is required before administering any magnesium supplementation 3
• Patients with symptomatic hypomagnesemia should be treated with intravenous magnesium, reserving oral replacement for asymptomatic patients 4
• Treatment of hypomagnesemia may involve withdrawal of certain medications, such as proton pump inhibitors (PPIs), and management with intravenous and oral magnesium and calcium replacement 5

Investigation of Hypomagnesemia

• The first step to determine the likely cause of hypomagnesemia is to measure fractional excretion of magnesium and urinary calcium-creatinine ratio 3
• Laboratory tests, including total serum magnesium, can be used to diagnose hypomagnesemia, although free magnesium is physiologically active 6
• Magnesium tolerance testing and ionized Mg2+ are alternative laboratory assessments, but each has its own difficulties in the ICU setting 7

Causes of Hypomagnesemia

• Hypomagnesemia may result from inadequate magnesium intake, increased gastrointestinal or renal losses, or redistribution from extracellular to intracellular space 3, 4, 5
• Certain medications, such as PPIs, can cause hypomagnesemia 4, 5
• Genetic or acquired renal disorders can also lead to hypomagnesemia 3