From the Guidelines
Hypomagnesemia is a condition characterized by low magnesium levels in the blood, and its treatment involves magnesium supplementation, with the approach depending on severity, as well as addressing underlying causes such as poor dietary intake, alcoholism, and certain medications. The condition is typically defined as serum magnesium below 1.8 mg/dL. According to the guidelines for management of patients with a short bowel 1, rehydration to correct secondary hyperaldosteronism is the most important first step in treating hypomagnesemia.
Causes and Symptoms
Causes of hypomagnesemia include:
- Poor dietary intake
- Alcoholism
- Certain medications (diuretics, proton pump inhibitors, antibiotics)
- Gastrointestinal disorders affecting absorption
- Kidney disease Symptoms may include:
- Muscle cramps
- Weakness
- Tremors
- Cardiac arrhythmias
- Seizures in severe cases
Treatment Approach
For mild cases, oral magnesium supplements like magnesium oxide are recommended, with a dose of 12–24 mmol daily 1. Magnesium oxide is commonly given and contains more elemental magnesium than other salts, and it is usually given at night when intestinal transit is assumed to be slowest and hence there is more time for absorption. If oral magnesium supplements do not normalize magnesium levels, oral 1-alpha hydroxy-cholecalciferol may be used, but regular monitoring of serum calcium is necessary to avoid hypercalcaemia 1. In severe cases, intravenous or subcutaneous infusion of magnesium may be necessary, usually with saline 1.
Management and Prevention
Addressing the underlying cause is crucial for long-term management, and magnesium-rich foods like nuts, seeds, whole grains, and leafy greens should be incorporated into the diet. Regular monitoring of serum magnesium levels is important during treatment to ensure normalization without overcorrection. As noted in the guidelines for management of patients with a short bowel 1, correction of water and sodium depletion, reduction of excess lipid in the diet, and use of oral 1 alpha cholecalciferol may also be beneficial in preventing and treating hypomagnesemia.
From the FDA Drug Label
As a nutritional adjunct in hyperalimentation, the precise mechanism of action for magnesium is uncertain. Early symptoms of hypomagnesemia (less than 1. 5 mEq/L) may develop as early as three to four days or within weeks. Predominant deficiency effects are neurological, e.g., muscle irritability, clonic twitching and tremors.
Hypocalcemia and hypokalemia often follow low serum levels of magnesium.
The causes of hypomagnesemia are not directly stated in the label, but the symptoms are:
- Neurological effects:
- Muscle irritability
- Clonic twitching
- Tremors
- Electrolyte imbalances:
- Hypocalcemia
- Hypokalemia 2
From the Research
Causes of Hypomagnesemia
- Inadequate magnesium intake 3
- Increased gastrointestinal or renal losses 3, 4
- Redistribution from extracellular to intracellular space 3
- Genetic or acquired renal disorders 3
- Certain medications such as loop diuretics and thiazide diuretics 3
- Conditions like Barter syndrome and Gitelman syndrome 3
Symptoms of Hypomagnesemia
- Most patients with hypomagnesemia are asymptomatic 3
- Symptoms usually do not arise until the serum magnesium concentration falls below 1.2 mg/dL 3
- Ventricular arrhythmia is one of the most life-threatening effects of hypomagnesemia 3
- Neurological and cardiovascular symptoms may occur depending on the severity of hypomagnesemia 5
- Hypokalemia, metabolic alkalosis, and hypercalciuria or hypocalciuria may also be present 3
Diagnosis and Treatment of Hypomagnesemia
- Measurement of fractional excretion of magnesium and urinary calcium-creatinine ratio can help determine the likely cause of hypomagnesemia 3
- Asymptomatic patients can be treated with oral magnesium supplements 3
- Parenteral magnesium should be reserved for symptomatic patients with severe magnesium deficiency (< 1.2 mg/dL) 3
- Intravenous or intramuscular magnesium sulfate can be used for urgent correction of hypomagnesemia 4
- Oral magnesium preparations are available for chronic use 4