Hypomagnesemia

Hypomagnesemia is a condition where your blood contains less magnesium than normal. This essential mineral plays a vital role in keeping your heart, brain, and muscles working properly, and low levels can lead to symptoms ranging from muscle cramps to dangerous heart rhythm problems.

Table of contents

• What is hypomagnesemia?
• Other names
• Who is affected?
• The role of magnesium in your body
• Symptoms and warning signs
• What causes hypomagnesemia?
• How is it diagnosed?
• Treatment options
• Prevention and outlook

What is hypomagnesemia?

Hypomagnesemia happens when you have a lower-than-normal level of magnesium in your blood. It can be mild or severe and is treatable^[1]. Normal blood magnesium levels are between 1.46 and 2.68 mg/dL, and hypomagnesemia is defined as levels below 1.46 mg/dL^[2]. However, this condition is typically asymptomatic (without symptoms) until serum magnesium concentration drops below 1.2 mg/dL^[2].

Magnesium is an electrolyte, which is a mineral that helps your body control many important functions. It’s the second-most abundant substance inside your cells and the fourth-most abundant overall in your body^[3]. Most of your body’s magnesium is stored in your bones, but only the magnesium dissolved in your blood is available for your cells and organs to use^[1].

magnesium deficiency, low blood magnesium

Other names

Hypomagnesemia is also known as magnesium deficiency or low blood magnesium^[4].

Who is affected?

Hypomagnesemia can affect anyone at any age. However, certain groups of people are at higher risk. It occurs in approximately 2% of the general U.S. population^[1]. The risk increases significantly in certain situations:

• 10% to 20% of people in the hospital have hypomagnesemia
• 50% to 60% of people in the intensive care unit (ICU) are affected
• 30% to 80% of people with alcohol use disorder have low magnesium levels
• 25% of people with poorly managed diabetes develop this condition^[1]

The role of magnesium in your body

Magnesium is essential for numerous processes in your body. It plays a fundamental role in energy transfer, storage, and use, as well as in protein, carbohydrate, and fat metabolism (the chemical processes that convert food into energy)^[3]. Your brain, heart, and muscles rely heavily on magnesium to do their job^[1].

Almost all enzymatic processes using phosphorus as an energy source require magnesium as a cofactor (a helper substance) or for activation. More than 600 enzymes need magnesium as a cofactor, and around 200 need it for activation^[3]. Magnesium also serves as a molecular stabilizer of RNA, DNA, and ribosomes, which are essential for cell function^[3].

Three organs are responsible for maintaining normal magnesium levels in your body. Your small and large intestines absorb magnesium from the food you eat. Your bones store most of your body’s magnesium supply. Your kidneys control how much magnesium is released through your urine^[1]. If there’s a problem in any step of this process, it can cause hypomagnesemia.

Magnesium has a direct effect on the balance of other electrolytes, including sodium, calcium, and potassium. Hypomagnesemia often happens alongside hypocalcemia (low blood calcium levels) and hypokalemia (low blood potassium levels)^[1].

Symptoms and warning signs

Hypomagnesemia can present in many different ways, but it mainly affects your neuromuscular system and heart. Some people don’t have any symptoms at all^[1].

When magnesium levels are mildly low, you may experience early signs such as having an upset stomach and a decreased appetite. You may even find yourself feeling weak and vomiting^[7]. Common symptoms of mild hypomagnesemia include:

• Tremors (shaking)
• Tetany (muscle spasms, muscle cramps, and numbness in your hands and feet)
• Abnormal eye movements called nystagmus
• Fatigue and weakness^[1]

When magnesium levels become severely low, symptoms can be more serious and include:

• Generalized tonic-clonic seizures (a type of seizure affecting the whole body)
• Delirium (sudden confusion and changes in thinking)
• Abnormal heart rhythms called arrhythmia, which can be life-threatening^[1]

Other symptoms that may occur include personality changes, numbness and tingling in your body, muscle fasciculations (visible muscle twitching under the skin), and hyperreflexia (overactive reflexes)^[5]. It’s important to seek medical care if you’re experiencing these symptoms.

What causes hypomagnesemia?

Hypomagnesemia usually happens due to one of the following reasons: too little intake of magnesium into your body, excessive loss of magnesium through your kidneys or gastrointestinal tract, or movement of magnesium from your blood into less accessible locations in your body (which is less common)^[1].

Too little intake of magnesium

Nutritional deficiencies due to poor intake of magnesium can result from:

• Starvation
• Alcohol use disorder with poor nutritional intake
• Anorexia nervosa
• Terminal cancer
• Critically ill people who cannot take food by mouth and must receive all their nutrients by IV^[2]

Deficiencies due to poor absorption of magnesium from the gastrointestinal tract can be caused by:

• Diseases causing malabsorption (inability to absorb nutrients properly) such as celiac disease and inflammatory bowel disease
• Gastric bypass surgery
• Hereditary syndromes causing poor absorption of magnesium (primary intestinal hypomagnesemia)
• Medications that interfere with magnesium absorption, such as proton pump inhibitors like omeprazole^[1]

Excessive loss of magnesium

Excessive losses of magnesium from the kidneys include:

• Alcohol use disorder
• Uncontrolled diabetes
• Inherited kidney tubular disorders, such as Gitelman syndrome
• Diuretic drugs (water pills) such as hydrochlorothiazide, chlorthalidone, furosemide, and bumetanide
• Aminoglycoside antibiotics (gentamicin, tobramycin, amikacin, plazomicin, streptomycin, neomycin)^[1]

Other medications that can cause hypomagnesemia include amphotericin B (used to treat fungal infections), cisplatin (a chemotherapy drug), cyclosporine and tacrolimus (immunosuppressant drugs), and certain drugs that target the epidermal growth factor receptor^[5].

Excessive losses from the gastrointestinal tract include chronic diarrhea, excessive vomiting or gastric suctioning, and pancreatitis (inflammation of the pancreas)^[5].

How is it diagnosed?

Hypomagnesemia is diagnosed by measuring the magnesium concentration in your blood. Your doctor will order a blood test to check your magnesium level^[1]. Normal range is 1.3 to 2.1 mEq/L (or 1.7 to 2.3 mg/dL in some references)^[4]. Severe hypomagnesemia usually results in concentrations of less than 1.25 mg/dL^[5].

Your doctor will also do a physical exam and ask about your symptoms. They may check for signs like abnormal eye movements, muscle spasms, or hyperreflexia (overactive reflexes)^[1]. In some cases, doctors may perform special tests like the Trousseau sign or Chvostek sign to check for tetany. Trousseau sign is tested by inflating a blood pressure cuff on your forearm to check for hand spasms. Chvostek sign is tested by tapping on your facial nerve to see if it causes facial muscle twitching^[5].

Other tests may be ordered to check for associated electrolyte abnormalities, such as low calcium and low potassium levels, which commonly occur with hypomagnesemia. An electrocardiogram (ECG) may be performed to check for heart rhythm problems^[1].

In patients with unexplained low calcium or difficult-to-treat low potassium, magnesium deficiency should be suspected even when serum magnesium concentration is normal. Magnesium deficiency should also be suspected in patients with unexplained neurologic symptoms and alcohol use disorder, chronic diarrhea, or after use of certain medications like cyclosporine, cisplatin-based chemotherapy, or prolonged therapy with amphotericin B or aminoglycosides^[5].

Treatment options

The treatment approach to hypomagnesemia depends on whether you have symptoms, how severe your symptoms are, and how low your magnesium levels are^[8]. For the most part, the signs and symptoms of hypomagnesemia are reversible with magnesium replacement^[1].

Oral magnesium replacement

If your magnesium levels are mildly low and you have no symptoms or only mild symptoms, oral magnesium supplements are usually recommended. Food is the best way to meet your body’s need for magnesium. Foods rich in magnesium include nuts, seeds, whole grains, beans and peas, and green vegetables^[6].

If you choose to take magnesium supplements, it’s important to stay below the upper limit for magnesium supplementation, which is 350 mg for most adults. High doses of magnesium can be dangerous^[6]. Oral magnesium replacement is the preferred route in asymptomatic children with mild hypomagnesemia and no gastrointestinal intolerance present, such as diarrhea, nausea, or vomiting^[13].

Sometimes oral magnesium supplements can cause diarrhea. If this happens, your doctor can adjust your dose^[16]. Speak to your doctor or pharmacist before taking a magnesium supplement^[7].

Intravenous (IV) magnesium replacement

Intravenous magnesium replacement is indicated in patients with severe symptoms such as hemodynamic instability, cardiac arrhythmias, tetany or seizures, or electrolyte abnormalities such as hypocalcemia or hypokalemia^[8]. If your levels are very low, you may need to be given magnesium by an intravenous drip in the hospital^[16].

Treatment can be started with 1-2 g (8-16 mEq) of magnesium sulfate infused over 2 to 15 minutes. This dose can be repeated as necessary to maintain the plasma magnesium concentration above 1.0 mg/dL^[8]. Nearly 50% of IV magnesium infused will be lost in urine because the increase in serum magnesium level decreases the gradient needed for reabsorption in the kidneys^[8].

Patients receiving intravenous magnesium replacement should be monitored for evidence of acute hypermagnesemia (too much magnesium), such as respiratory depression or loss of reflexes^[8].

Addressing the underlying cause

Sources of magnesium loss may also need to be addressed. For example, if diuretic use is causing hypomagnesemia, your doctor may need to adjust your medication^[1]. Hypomagnesemia treatment should also include addressing the underlying cause^[6].

Hypomagnesemia often leads to hypokalemia and hypocalcemia. These low calcium and potassium levels do not resolve until the magnesium deficiency has been corrected^[8].

Prevention and outlook

Prevention is important, especially if you have risk factors for developing hypomagnesemia. 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 that contain electrolytes to keep your magnesium level in a healthy range^[4].

The outcome depends on the condition that is causing the problem^[4]. If left untreated, hypomagnesemia can lead to serious complications including cardiac arrest, respiratory arrest, and death^[4]. Untreated low magnesium can cause the heart to beat irregularly, and you could be especially at risk for torsades de pointes, a type of dangerous irregular heart rhythm^[6].

At least one study found that people with diabetes who have low magnesium are at greater risk of diabetes complications, such as foot ulcers, vision problems, and a decrease in kidney function. Some experts believe hypomagnesemia worsens insulin resistance, which in turn worsens hypomagnesemia, creating a downward spiral^[6].

When your body’s magnesium level drops too much, it can be a life-threatening emergency. You should call your healthcare provider right away if you have symptoms of this condition^[4].