Magnesium

Most of the body's magnesium occurs in bone; very little is present in the blood. Magnesium is necessary for the formation of bone and teeth and for normal nerve and muscle function. Many enzymes in the body depend on magnesium to function normally. The body takes in magnesium from the diet and excretes it in urine and stool.

Hypomagnesemia

In hypomagnesemia, the level of magnesium in the blood is too low. The most common causes of hypomagnesemia are decreased dietary intake (due to starvation) and decreased intestinal absorption (malabsorption). Hypomagnesemia occurs frequently in people who consume large amounts of alcohol and in people who have protracted diarrhea. Hypomagnesemia can also be caused by increased excretion of magnesium by the kidneys. High levels of aldosterone, antidiuretic hormone, or thyroid hormones can cause hypomagnesemia by increasing the excretion of magnesium by the kidneys. Diuretics, the antifungal drug amphotericin B, or the chemotherapy drug cisplatin can also cause hypomagnesemia.

Symptoms of hypomagnesemia include nausea, vomiting, sleepiness, weakness, personality changes, muscle spasms, tremors, and loss of appetite. The diagnosis is made by determining that the magnesium level in the blood is low.

Magnesium is replaced when the deficiency causes symptoms or when the magnesium level is very low. Magnesium can be taken by mouth (usually as small amounts of magnesium hydroxide) or by injection into a muscle or vein.

Hypermagnesemia

In hypermagnesemia, the level of magnesium in the blood is too high. Hypermagnesemia usually develops only in people with kidney failure who are given magnesium salts or who take drugs that contain magnesium (such as some antacids or laxatives).

Symptoms of hypermagnesemia include weakness, low blood pressure, and impaired breathing. When hypermagnesemia is severe, the heart can stop beating. The diagnosis is made by determining that the magnesium level in the blood is high.

People with severe hypermagnesemia are given intravenous calcium gluconate. Intravenous diuretics can increase the kidneys' excretion of magnesium, but if the kidneys are not functioning well, dialysis is usually needed.