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Hypomagnesemia (Low Magnesium)

Overview

Magnesium is one of the most abundant essential minerals in your body. It’s primarily stored in the bones of your body. A very small amount of magnesium circulates in your bloodstream.

Magnesium plays a role in over 300 metabolic reactions in your body. These reactions impact a number of very important body processes, including:

  • protein synthesis
  • cellular energy production and storage
  • stabilization of cells
  • DNA synthesis
  • nerve signal transmission
  • bone metabolism
  • cardiac function
  • the conduction of signals between muscles and nerves
  • glucose and insulin metabolism
  • blood pressure
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Symptoms

Symptoms of low magnesium

Early signs of low magnesium include:

  • nausea
  • vomiting
  • weakness
  • decreased appetite

As magnesium deficiency worsens, symptoms may include:

Causes

Causes of low magnesium

Low magnesium is typically due to decreased absorption of magnesium in the gut or increased excretion of magnesium in the urine. Low magnesium levels in otherwise healthy people are uncommon. This is because magnesium levels are largely controlled by the kidneys. The kidneys increase or decrease excretion (waste) of magnesium based on what the body needs.

Continually low dietary intake of magnesium, excessive loss of magnesium, or the presence of other chronic conditions can lead to hypomagnesemia.

Hypomagnesemia is also more common in people who are hospitalized. This may be due to their illness, having certain surgeries, or taking certain types of medication. Very low magnesium levels have been linked to poorer outcomes for severely ill, hospitalized patients.

Conditions that increase the risk of magnesium deficiency include gastrointestinal (GI) diseases, advanced age, type 2 diabetes, use of loop diuretics (such as Lasix), treatment with certain chemotherapies, and alcohol dependence.

GI diseases

Celiac disease, Crohn’s disease, and chronic diarrhea can impair the absorption of magnesium or result in increased magnesium loss.

Type 2 diabetes

Higher concentrations of blood glucose can cause the kidneys to excrete more urine. This also causes increased loss of magnesium.

Alcohol dependence

Alcohol dependence can lead to:

  • poor dietary intake of magnesium
  • increase in urination and fatty stools
  • liver disease
  • vomiting
  • kidney impairment
  • pancreatitis
  • other complications

All of these conditions have the potential to result in hypomagnesemia.

Older adults

Gut absorption of magnesium tends to decrease with age. Urinary output of magnesium tends to increase with age. Older adults often eat fewer magnesium-rich foods. They’re also more likely to take medication that can affect magnesium (such as diuretics). These factors can lead to hypomagnesemia in older adults.

Use of diuretics

Use of loop diuretics (such as Lasix) can sometimes lead to loss of electrolytes such as potassium, calcium, and magnesium.

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Diagnosis

Diagnosis of low magnesium

Your doctor will diagnose hypomagnesemia based on a physical exam, symptoms, medical history, and a blood test. A blood magnesium level doesn’t tell you the amount of magnesium your body has stored in your bones and muscle tissue. But it’s still helpful for indicating whether you have hypomagnesemia. Your doctor will likely also check your blood calcium and potassium levels.

A normal serum (blood) magnesium level is 1.8 to 2.2 milligrams per deciliter (mg/dL). Serum magnesium lower than 1.8 mg/dL is considered low. A magnesium level below 1.25 mg/dL is considered very severe hypomagnesemia.

Treatment

Treatment of low magnesium

Hypomagnesemia is typically treated with oral magnesium supplements and increased intake of dietary magnesium.

An estimated 2 percent of the general population has hypomagnesemia. This percentage is much higher in hospitalized people. Studies estimate that nearly half of all Americans — and 70 to 80 percent of those over the age of 70 — aren’t meeting their daily recommended magnesium needs. Getting your magnesium from food is best, unless your doctor tells you otherwise.

Examples of magnesium-rich foods include:

  • spinach
  • almonds
  • cashews
  • peanuts
  • whole grain cereal
  • soymilk
  • black beans
  • whole wheat bread
  • avocado
  • banana
  • halibut
  • salmon
  • baked potato with the skin

If your hypomagnesemia is severe and includes symptoms such as seizures, you may receive magnesium intravenously, or by IV.

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Complications

Complications of low magnesium

If hypomagnesemia and its underlying cause remain untreated, severely low magnesium levels can develop. Severe hypomagnesemia can have life-threatening complications such as:

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Outlook

Outlook for low magnesium

Hypomagnesemia can be caused by a variety of underlying conditions. It can be treated very effectively with oral or IV magnesium. It’s important to eat a balanced diet to ensure you’re getting enough magnesium. If you have conditions such as Crohn’s disease or diabetes, or take diuretic medications, work with your doctor to ensure that you don’t develop low magnesium. If you have symptoms of low magnesium, it’s important to see your doctor to prevent the development of complications.

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