Every organ in the body, especially the heart, muscles, and kidneys, needs the mineral magnesium. It also contributes to the makeup of teeth and bones. Magnesium is needed for many functions in the body. This includes the physical and chemical processes in the body that convert or use energy (metabolism).

When the level of magnesium in the body drops below normal, symptoms may develop due to low magnesium.

Common causes of low magnesium include:

• Alcohol use
• Burns that affect a large area of the body
• Chronic diarrhea
• Excessive urination (polyuria), such as in uncontrolled diabetes and during recovery from acute kidney injury
• Hyperaldosteronism (disorder in which the adrenal gland releases too much of the hormone aldosterone into the blood)
• Kidney tubule disorders
• Malabsorption syndromes, such as celiac disease and inflammatory bowel disease
• Malnutrition
• Medicines including amphotericin, antibodies targeting the epidermal growth factor (EGF) receptor, cisplatin, cyclosporine, diuretics, proton pump inhibitors, tacrolimus, and aminoglycoside antibiotics
• Pancreatitis (swelling and inflammation of the pancreas)
• Excessive sweating

Common symptoms include:

• Abnormal eye movements (nystagmus)
• Convulsions
• Fatigue
• Muscle spasms or cramps
• Muscle weakness
• Numbness

Your health care provider will do a physical exam and ask about your symptoms.

Tests that may be ordered include an electrocardiogram (ECG).

A blood test will be ordered to check your magnesium level. The normal range is 1.6 to 2.6 mg/dL (0.66 to 1.07 mmol/L).

Normal value ranges may vary slightly among different laboratories. Talk to your provider about the meaning of your specific test result.

Other blood and urine tests that may be done include:

• Calcium blood test
• Comprehensive metabolic panel
• Potassium blood test
• Urine magnesium test

Treatment depends on the severity of the low magnesium problem and may include:

• Fluids given through a vein (IV)
• Magnesium by mouth or through a vein
• Medicines to relieve symptoms

The outcome depends on the condition that is causing the problem and the severity of the magnesium deficiency.

Untreated, this condition can lead to:

• Cardiac arrest
• Respiratory arrest
• Death

When your body's magnesium level drops too much, it can be a life-threatening emergency. Contact your provider right away if you have symptoms of this condition.

Treating the condition that is causing low magnesium can help.

If you play sports or do other vigorous activity, drink fluids such as sports drinks. They contain electrolytes to keep your magnesium level in a healthy range.

Low blood magnesium; Magnesium - low; Hypomagnesemia

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Pfennig CL, Slovis CM. Electrolyte disorders. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 114.

Yu ASL. Disorders of magnesium and phosphorus. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 105.

Updated by: Jacob Berman, MD, MPH, Clinical Assistant Professor of Medicine, Division of General Internal Medicine, University of Washington School of Medicine, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.