Hypomagnesemia

Overview

Hypomagnesemia means the level of magnesium in the blood is too low. Magnesium is a mineral and electrolyte that plays a part in hundreds of body processes, including muscle and nerve function, heart rhythm, blood pressure, blood sugar control, and bone health. It also affects the balance of other electrolytes such as potassium and calcium.

Low magnesium can be mild and cause no symptoms, or it can be severe enough to cause muscle problems, dangerous heart rhythms, and seizures. It often occurs alongside low levels of potassium or calcium, and correcting magnesium can be necessary to fix those imbalances too. Treatment involves replacing magnesium and addressing the underlying cause.

Symptoms

Mild hypomagnesemia may cause no symptoms and is often discovered on a routine blood test. As levels drop further, symptoms can include:

• Muscle cramps, twitches, or spasms, sometimes involving the hands, feet, or face.
• Weakness and fatigue.
• Numbness or tingling, especially around the mouth or in the fingers.
• Tremor and, in severe cases, jerking movements.
• Nausea and loss of appetite.
• Abnormal heart rhythms or palpitations, which can be serious and even life-threatening.
• Personality changes, irritability, anxiety, or confusion.
• Seizures in severe cases.

Because magnesium affects other electrolytes, symptoms of low potassium or low calcium often occur at the same time, and these overlapping deficiencies can make the symptoms harder to control until magnesium is corrected. The severity of symptoms depends on how low the level is and how quickly it fell.

Causes

Low magnesium results from losing too much, taking in too little, or shifting magnesium within the body. Causes include:

• Digestive losses from chronic diarrhea, vomiting, or conditions that reduce absorption, such as celiac disease, Crohn disease, or surgery affecting the intestine.
• Alcohol use disorder, a common cause through poor intake and increased losses.
• Certain medications, including some diuretics (water pills), long-term use of certain acid-reducing drugs, and some chemotherapy and antibiotic agents.
• Poorly controlled diabetes.
• Kidney problems that cause excess magnesium loss in the urine.
• Poor dietary intake, especially with malnutrition.

Risk Factors

People more likely to develop low magnesium include those with:

• Alcohol use disorder.
• Digestive diseases that reduce absorption or cause chronic diarrhea.
• Long-term use of diuretics or certain acid-reducing medications.
• Poorly controlled diabetes.
• Critical illness or hospitalization.
• Older age and poor nutrition.

Diagnosis

Hypomagnesemia is diagnosed and evaluated with blood tests and a review of the person's situation:

• A blood test measuring the magnesium level, often done along with potassium, calcium, sodium, and kidney function.
• Review of medications and medical history, including alcohol use and digestive conditions.
• An electrocardiogram (ECG) to check for heart rhythm changes if levels are low or symptoms are present.
• Urine tests in some cases to determine whether magnesium is being lost through the kidneys or the gut.

Because low magnesium frequently occurs with other electrolyte problems, those are checked and treated together.

Treatment

Treatment depends on how low the level is, whether there are symptoms, and the cause:

• Oral magnesium supplements for mild cases without serious symptoms, along with magnesium-rich foods.
• Intravenous (IV) magnesium in a hospital for severe deficiency, significant symptoms, or dangerous heart rhythms.
• Correcting other electrolytes, since low potassium and calcium often improve once magnesium is replaced.
• Treating the underlying cause, such as adjusting medications, managing alcohol use, treating diarrhea, or controlling diabetes.

Magnesium-rich foods include green leafy vegetables, nuts, seeds, whole grains, and legumes, which can help maintain healthy levels. When magnesium is replaced gradually with supplements, some people experience loose stools, so the dose may be adjusted for comfort. In severe or symptomatic cases, replacement is given carefully in the hospital with monitoring of the heart rhythm and blood levels, because correcting magnesium too quickly can also cause problems. Ongoing treatment may be needed for people whose underlying cause continues, such as those who must keep taking a medication that lowers magnesium.

Prevention

Steps that help prevent low magnesium include:

• Eating a balanced diet that includes magnesium-rich foods such as leafy greens, nuts, seeds, whole grains, and beans.
• Managing chronic conditions such as diabetes and digestive diseases.
• Limiting alcohol.
• Reviewing long-term medications with a doctor, including diuretics and acid reducers, so magnesium can be monitored if needed.
• Following up on lab tests if you have a condition that lowers magnesium.

When to See a Doctor

See a doctor if you have ongoing muscle cramps, weakness, numbness, or fatigue, especially if you have a condition or take a medication that can lower magnesium. A simple blood test can check your level.

Seek emergency care for a fast, irregular, or pounding heartbeat with dizziness or fainting, chest pain, or a seizure. Severe hypomagnesemia can cause dangerous heart rhythms and seizures that need immediate treatment.

Related Topics

Frequently Asked Questions

References

1. MedlinePlus, U.S. National Library of Medicine.
2. Mayo Clinic.
3. National Institutes of Health, Office of Dietary Supplements.