A mineral found in the fluid that surrounds cells, magnesium (Mg) is an essential component of more than 300 enzymes that regulate many body functions. Imbalances occur when the blood contains more or less magnesium than it should.
Magnesium is necessary for the formation and functioning of healthy bones, teeth, muscles, and nerves. It converts food into energy, builds proteins, and is instrumental in maintaining adequate levels of calcium in the blood. Magnesium helps prevent cardiovascular disease and irregular heartbeat, reduces the risk of bone loss (osteoporosis), and increases an individual's chance of surviving a heart attack. It may also help prevent stroke and lessen the effects of existing osteoporosis.
Fish, dairy products, leafy green vegetables, legumes, nuts, seeds, and grains are especially good sources of magnesium, but varying amounts of this mineral are found in all foods. Some is stored in the kidneys, and excess amounts are excreted in the urine or stools.
Magnesium deficiency (hypomagnesemia) or excess (hypermagnesemia) is rare, but either condition can be serious.
Causes & symptoms
Magnesium deficiency most often occurs in people who have been fed intravenously for a long time, whose diet doesn't contain enough magnesium, or who are unable to absorb and excrete the mineral properly.
Secreting too much aldosterone (the hormone that regulates the body's salt-fluid balance), ADH (a hormone that inhibits urine production), or thyroid hormone can cause hypomagnesemia.
Other factors associated with hypomagnesemia include:
- Loss of body fluids as a result of stomach suctioning or chronic diarrhea
- Cisplatin (a chemotherapy drug)
- Long-term diuretic therapy
- Hypercalcemia (abnormally high levels of calcium in the blood)
- Diabetic acidosis (a condition in which the body's tissues have a higher-than-normal acid content)
- Complications of bowel surgery
- Chronic alcoholism
- Severe dehydration.
People who have hypomagnesemia usually experience loss of weight and appetite, bloating, and muscle pain, and they pass stools that have a high fat content. Also, they may be listless, disoriented, confused, and very irritable. Other symptoms of hypomagnesemia are:
- Muscle weakness
- Irregular heart beat
- Delusions and hallucinations
- Leg and foot cramps
- Muscle twitches
- Changes in blood pressure.
Severe magnesium deficiency can cause seizures, especially in children.
Neonatal hypomagnesemia can occur in premature babies and in infants who have genetic parathyroid disorders or who have had blood transfusions. This condition also occurs in babies born to magnesium-deficient mothers or to women who have:
- Diabetes mellitus.
- Hyperparathyroidism (overactive parathyroid glands)
- Toxemia (a pregnancy-related condition characterized by high blood pressure and fluid retention).
Hypermagnesemia is most common in patients whose kidneys cannot excrete the magnesium they derive from food or take as medication. This condition can also develop in patients who take magnesium salts, or in healthy people who use large quantities of magnesium-containing antacids, laxatives, or analgesics (pain relievers).
Magnesium poisoning can cause severe diarrhea in young people, and mask the symptoms of other illnesses. Very high overdoses can lead to coma. The risk of complications of magnesium poisoning is greatest for:
- Elderly people with inefficient kidney function
- Patients with kidney problems or intestinal disorders
- People who use antihistamines, muscle relaxants, or narcotics.
Severe dehydration or an overdose of supplements taken to counteract hypomagnesemia can also cause this condition.
People who have hypermagnesemia may feel flushed and drowsy, perspire heavily, and have diarrhea. Breathing becomes shallow, reflexes diminish, and the patient becomes unresponsive. Muscle weakness and hallucinations are common. The patient's heart beat slows dramatically and blood pressure plummets. Extreme toxicity, which can lead to coma and cardiac arrest, can be fatal.
Blood tests are used to measure magnesium levels.
The goal of treatment is to identify and correct the cause of the imbalance. Oral magnesium supplements or injections are usually prescribed to correct mild magnesium deficiency. If the deficiency is more severe or does not respond to treatment, magnesium sulfate or magnesium chloride may be administered intravenously.
Doctors usually prescribe diuretics (urine-producing drugs) for patients with hypermagnesemia and advise them to drink more fluids to flush the excess mineral from the body. Patients whose magnesium levels are extremely high may need mechanical support to breathe and to circulate blood throughout their bodies.
Intravenously administered calcium gluconate may reverse damage caused by excess magnesium. Intravenous furosemide (Lasix) or ethacrynic acid (Edecrin) can increase magnesium excretion in patients who get enough fluids and whose kidneys are functioning properly.
In an emergency, dialysis can provide temporary relief for patients whose kidney function is poor or who are unable to excrete excess minerals.
Because imbalances may recur if the underlying condition is not eliminated, monitoring of magnesium levels should continue after treatment has been completed.
Most people consume adequate amounts of magnesium in the food they eat. Dietary supplements can be used safely, but should only be used under a doctor's supervision.
- An abnormally high concentration of magnesium in the blood.
- An abnormally low concentration of magnesium in the blood.
Gale Encyclopedia of Medicine. Gale Research, 1999.