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Hypomagnesemia (Low Level of Magnesium in the Blood)


James L. Lewis, III

, MD, Brookwood Baptist Health and Saint Vincent’s Ascension Health, Birmingham

Last full review/revision Apr 2020| Content last modified Apr 2020
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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.


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.


  • 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.


  • Magnesium

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.

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