Magnesium is one of the body's electrolytes, which are minerals that carry an electric charge when dissolved in body fluids such as blood, but the majority of magnesium in the body is uncharged and bound to proteins or stored in bone. Although blood contains very little magnesium, some is still necessary for normal nerve and muscle function and for development of bone and teeth.
Usually, the magnesium level becomes low because people consume less (most often, because of starvation) or because the intestine cannot absorb nutrients normally (called malabsorption). But sometimes hypomagnesemia develops because the kidneys or intestine excrete too much magnesium.
Hypomagnesemia may also result from the following:
Consuming large amounts of alcohol (common), which reduces consumption of food (and thus magnesium) and increases excretion of magnesium
Protracted diarrhea (common), which increases magnesium excretion
High levels of aldosterone, vasopressin (antidiuretic hormone), or thyroid hormones, which increase magnesium excretion
Drugs that increase magnesium excretion, including diuretics, the antifungal drug amphotericin B, and the chemotherapy drug cisplatin
Chronic use of a proton pump inhibitor (certain stomach acid reducing drugs)
Breastfeeding, which increases requirements for magnesium
Hypomagnesemia may cause nausea, vomiting, sleepiness, weakness, personality changes, muscle spasms, tremors, and loss of appetite. If severe, hypomagnesemia can cause seizures, especially in children.
Magnesium is given by mouth when the deficiency causes symptoms or persists. People with alcoholism are usually given magnesium.
If a very low magnesium level is causing severe symptoms or if people cannot take magnesium by mouth, magnesium is given by injection into a muscle or vein.
When treating hypomagnesemia, doctors also must correct other electrolyte abnormalities, such as hypocalcemia and hypokalemia.