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Hypomagnesemia (Low Level of Magnesium in the Blood)

By James L. Lewis, III, MD, Attending Physician, Brookwood Baptist Health and Saint Vincent’s Ascension Health, Birmingham

In hypomagnesemia, the level of magnesium in blood is too low.

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.

Causes of Hypomagnesemia

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 excretion

  • High levels of aldosterone, vasopressin (antidiuretic hormone), or thyroid hormones, which increase excretion

  • Drugs that increase excretion, including diuretics, the antifungal drug amphotericin B, and the chemotherapy drug cisplatin

  • Chronic use of a protein pump inhibitor (certain stomach acid reducing drugs)

  • Breastfeeding, which increases requirements for magnesium

Symptoms of Hypomagnesemia

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.

Diagnosis of Hypomagnesemia

  • Measurement of magnesium level in the blood

The diagnosis is usually based on blood tests indicating that the magnesium level is low. Hypocalcemia and hypokalemia also may be present.

Treatment of Hypomagnesemia

  • Magnesium

Magnesium is given by mouth when the deficiency causes symptoms or persists. All people with alcoholism are 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 levels, such as calcium and potassium.

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