From the Guidelines
Magnesium deficiency and toxicity can have severe consequences, including cardiac arrhythmias, and it is essential to monitor and manage magnesium levels to prevent these complications. The side effects of hypomagnesemia (magnesium deficiency) include ventricular arrhythmias, likely caused by diuresis, and can be treated with magnesium supplements, which have been shown to significantly reduce the frequency of premature ventricular contractions (PVCs) in hospitalized patients with heart failure 1. Some of the symptoms of magnesium deficiency include:
- Muscle cramps
- Tremors
- Fatigue
- Irregular heartbeat
- Numbness
- Tingling
- Seizures
- Personality changes
- Nausea
- Coronary spasms in severe cases On the other hand, hypermagnesemia (magnesium toxicity) is less common but can occur in patients with renal dysfunction or as an iatrogenic overdose, particularly in pregnant women receiving magnesium for preterm labor 1. The symptoms of magnesium toxicity include:
- Nausea
- Vomiting
- Facial flushing
- Low blood pressure
- Lethargy
- Confusion
- Muscle weakness
- Difficulty breathing
- Irregular heartbeat
- Cardiac arrest in extreme cases Magnesium levels of 2.5 to 5 mmol/L may manifest as prolonged PR, QRS, and QT intervals, while severely elevated levels of 6 to 10 mmol/L may result in atrioventricular nodal conduction block, bradycardia, hypotension, and cardiac arrest 1. It is crucial to monitor magnesium levels and use electrocardiographic monitoring among hospitalized patients with moderate and severe imbalances of potassium or magnesium to prevent or intervene for lethal cardiac rhythms. In patients with suspected magnesium deficiency, supplements like magnesium oxide, magnesium citrate, or magnesium glycinate may be prescribed, but people with kidney disease should avoid supplementation without medical supervision due to the risk of toxicity 1. Blood tests can confirm magnesium status, with normal serum levels ranging from 1.7-2.2 mg/dL, and differing normal values are reported, but <1.3 mEq/L is undisputedly low 1.
From the FDA Drug Label
As plasma magnesium rises above 4 mEq/L, the deep tendon reflexes are first decreased and then disappear as the plasma level approaches 10 mEq/L. At this level respiratory paralysis may occur. Heart block also may occur at this or lower plasma levels of magnesium. Serum magnesium concentrations in excess of 12 mEq/L may be fatal. 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. The adverse effects of parenterally administered magnesium usually are the result of magnesium intoxication. These include flushing, sweating, hypotension, depressed reflexes, flaccid paralysis, hypothermia, circulatory collapse, cardiac and CNS depression proceeding to respiratory paralysis.
The side effects of hypomagnesemia (magnesium deficiency) are:
- Muscle irritability
- Clonic twitching
- Tremors
- Hypocalcemia
- Hypokalemia
The side effects of hypermagnesemia (magnesium toxicity) are:
- Flushing
- Sweating
- Hypotension
- Depressed reflexes
- Flaccid paralysis
- Hypothermia
- Circulatory collapse
- Cardiac and CNS depression
- Respiratory paralysis
- Heart block 2, 2
From the Research
Hypomagnesemia (Magnesium Deficiency)
- Hypomagnesemia is defined as a serum magnesium level less than 1.8 mg/dL (< 0.74 mmol/L) 3
- It may result from inadequate magnesium intake, increased gastrointestinal or renal losses, or redistribution from extracellular to intracellular space 3
- Symptoms usually do not arise until the serum magnesium concentration falls below 1.2 mg/dL 3
- One of the most life-threatening effects of hypomagnesemia is ventricular arrhythmia 3
- Low magnesium status has been identified as a significant risk factor for several diseases, including type-2 diabetes, cardiovascular diseases, arrhythmias, as well as general muscular and neurological problems 4, 5, 6, 7
Hypermagnesemia (Magnesium Toxicity)
- There is limited information available on the effects of hypermagnesemia in the provided studies
- However, it is mentioned that imbalances in magnesium status, primarily hypomagnesemia, might result in unwanted neuromuscular, cardiac or nervous disorders, implying that hypermagnesemia may also have adverse effects 6
Health Consequences of Magnesium Imbalance
- Magnesium deficiency can have serious health consequences, including increased risk of type 2 diabetes and cardiovascular diseases 5, 6
- Low levels of magnesium have been associated with a number of chronic diseases, such as Alzheimer's disease, insulin resistance and type-2 diabetes mellitus, hypertension, cardiovascular disease, migraine headaches, and attention deficit hyperactivity disorder (ADHD) 6
- Clinical magnesium deficiency may result in hypokalaemia, hypocalcaemia or other disturbances of electrolyte homeostasis, refractory cardiac arrhythmias, or increased sensitivity to digoxin 7