From the Guidelines
Hypomagnesemia should be treated with oral magnesium supplementation for mild to moderate cases, and intravenous replacement for severe cases or when symptoms like seizures, arrhythmias, or tetany are present, as it is essential for over 300 enzymatic reactions in the body, including nerve and muscle function, protein synthesis, and energy production.
Definition and Causes
Hypomagnesemia is a condition characterized by abnormally low levels of magnesium in the blood, typically defined as serum magnesium below 1.8 mg/dL [ 1 ]. It usually results from decreased absorption or increased loss of magnesium from either the kidneys or intestines (diarrhea), alterations in thyroid hormone function, certain medications (eg, pentamidine, diuretics, alcohol), and malnourishment [ 1 ].
Treatment
For mild to moderate cases (1.0-1.7 mg/dL), oral magnesium supplementation is recommended, such as magnesium oxide 400-800 mg daily, magnesium citrate 200-400 mg daily, or magnesium glycinate 200-400 mg daily, divided into 2-3 doses to improve tolerance.
- Key considerations:
- Monitoring and correcting potassium and calcium levels simultaneously, as hypomagnesemia often accompanies other electrolyte disturbances.
- Addressing underlying causes, including discontinuing medications that deplete magnesium (diuretics, proton pump inhibitors, certain antibiotics), treating malabsorption issues, or controlling diabetes.
- For severe hypomagnesemia (below 1.0 mg/dL) or when symptoms like seizures, arrhythmias, or tetany are present, intravenous replacement is necessary, typically with 1-2 grams of magnesium sulfate over 15-30 minutes for urgent situations, followed by slower infusion of 4-8 grams over 24 hours [ 1 ].
Importance of Magnesium
Magnesium is an essential electrolyte and an important cofactor for multiple enzymes, including ATPase, and plays a crucial role in stabilizing excitable membranes [ 1 ]. The presence of a low plasma magnesium concentration has been associated with poor prognosis in cardiac arrest patients [ 1 ].
Clinical Considerations
In clinical practice, it is crucial to be aware of the potential for hypomagnesemia, especially in patients with risk factors such as malabsorption, certain medications, or underlying medical conditions [ 1 ]. Prompt recognition and treatment of hypomagnesemia can significantly improve patient outcomes, reducing morbidity, mortality, and enhancing quality of life.
From the Research
Definition and Causes of Hypomagnesemia
- Hypomagnesemia is defined as a serum magnesium level less than 1.8 mg/dL (< 0.74 mmol/L) 2
- It may result from inadequate magnesium intake, increased gastrointestinal or renal losses, or redistribution from extracellular to intracellular space 2, 3
- Increased renal magnesium loss can result from genetic or acquired renal disorders 2
Symptoms and Effects of Hypomagnesemia
- Most patients with hypomagnesemia are asymptomatic and symptoms usually do not arise until the serum magnesium concentration falls below 1.2 mg/dL 2
- One of the most life-threatening effects of hypomagnesemia is ventricular arrhythmia 2
- Hypomagnesemia can also lead to secondary hypocalcemia, as seen in a patient with short bowel syndrome and PPI therapy 3
Diagnosis and Evaluation of Hypomagnesemia
- The first step to determine the likely cause of the hypomagnesemia is to measure fractional excretion of magnesium and urinary calcium-creatinine ratio 2
- A fractional excretion above 2% in a subject with normal kidney function indicates renal magnesium wasting 2
- Barter syndrome, loop diuretics, Gitelman syndrome, and thiazide diuretics can all lead to renal magnesium wasting and hypomagnesemia 2
Treatment of Hypomagnesemia
- Asymptomatic patients should be treated with oral magnesium supplements 2
- Parenteral magnesium should be reserved for symptomatic patients with severe magnesium deficiency (< 1.2 mg/dL) 2
- Establishment of adequate renal function is required before administering any magnesium supplementation 2
- In some cases, treatment may involve withdrawal of offending medications, such as proton pump inhibitors (PPIs), and management with intravenous and oral magnesium and calcium replacement 3