Magnesium is an essential mineral that drives many important processes in the body: energy production, protein synthesis, DNA creation, nerve conduction, muscle contraction, blood pressure, blood glucose regulation, bone health, and heart rate regulation. Low magnesium describes a situation where magnesium levels in the blood are less than 1.85 mg per deciliter (0.75 millimoles per liter). However, only 2.6% of magnesium in the body is in the blood, so low magnesium levels may not mean magnesium deficiency throughout the body. Most magnesium is in the fluids surrounding the body’s cells, and the rest is stored in the bones. However, our only way of measuring magnesium in the body is to measure the amount of magnesium in the blood.
The kidneys largely regulate blood magnesium levels. That means that there are three possible reasons that blood magnesium levels get too low. The first possible reason is a magnesium deficiency. A person with low magnesium may not have enough magnesium in their diet. Alternatively, magnesium absorption by the digestive system may be dysfunctional, and most of the magnesium they’re eating is excreted. The second possibility is the kidneys eliminating too much magnesium in the urine. The third possibility is the magnesium in the blood being drawn into the body’s tissues or bones instead. The body may have enough magnesium, but blood levels are low. In any case, low magnesium levels in the body can cause problems, some of them serious and even life-threatening. Muscle weakness, nerve problems, personality changes, low calcium, low potassium, low phosphate, vitamin D deficiency, parathyroid gland dysfunction, osteoporosis, high blood pressure, and abnormal heart rhythms (arrhythmias) are all possible consequences of magnesium deficiency.
Low magnesium is a common health condition that primarily affects people who abuse alcohol, have diabetes, are pregnant, are critically ill, or are hospitalized.
Nutritional deficiencies, gastrointestinal problems, kidney disorders, critical illnesses, pregnancy, uncontrolled diabetes, alcohol abuse, or medication side effects cause low magnesium.
Risk factors for low magnesium include chronic disease, critical illness, chronic diarrhea, alcohol use disorder, hospitalization, intravenous feeding, and certain drugs, such as loop diuretics or proton pump inhibitors.
Symptoms of low magnesium include reduced appetite, nausea, vomiting, lethargy, tiredness, weakness, personality changes, muscle spasms, muscle cramps, numbness, tingling, overactive reflexes, tremors, abnormal heartbeats, palpitations, rapid eye movements (nystagmus), and seizures.
Low magnesium usually requires a medical diagnosis.
Low magnesium generally requires treatment. It typically resolves with treatment, but the timeframe will depend on the underlying cause.
Treatment of low magnesium may include oral magnesium supplements or intravenous magnesium sulfate solution.
Low magnesium may be preventable by diet and managing chronic conditions.
Save on prescriptions for low magnesium with a SingleCare prescription discount card.
The most common low magnesium causes are:
Diabetes mellitus (about 26% to 39% prevalence)
Alcohol abuse (about 30% prevalence)
Hospitalization (about 7 to 11% prevalence), particularly critically ill patients in an ICU (up to 65% prevalence)
Low magnesium is caused by either too little magnesium entering the body or too much magnesium leaving the body. In turn, insufficient magnesium enters the body either because of poor diet or poor digestion. Excessive magnesium loss is due to kidney issues. Since low magnesium only applies to magnesium levels in the blood, low magnesium can also be due to conditions that draw magnesium out of the blood and into the body’s tissues or bones.
Insufficient magnesium intake causes include:
Malnutrition
Alcohol use disorder (when associated with poor nutrition)
IV feeding
On the other hand, people may be consuming enough magnesium, but not enough is absorbed by the gastrointestinal system. Instead, dietary magnesium is being passed in the stools. There are many reasons for this:
Celiac disease
Inflammatory bowel disease (Crohn’s disease or ulcerative colitis)
Acute pancreatitis
Gastric bypass surgery
Removal of part of the small intestine (small bowel bypass)
Congenital disorders that cause intestinal malabsorption
Alcohol use disorder
Laxative abuse
Chronic use of proton pump inhibitors
Medication side effects
Excessive magnesium loss is due to magnesium excretion through the kidneys. This can be caused by:
Alcohol use disorder
Uncontrolled diabetes
Acidosis
Hypercalcemia (high calcium)
Hyperthyroidism (overactive thyroid)
Hereditary kidney dysfunction
Kidney transplant
Kidney injury
Dialysis
Side effects of kidney-damaging drugs, such as aminoglycoside antibiotics, certain types of tuberculosis antibiotics, chemotherapy drugs, some immune-suppressing drugs, the antibiotic pentamidine, the heart failure drug digoxin, and the antifungal drug amphotericin B.
Finally, the body sometimes pulls magnesium out of the bloodstream and moves it to the fluids between its cells or deposits it in the bones. The total amount of magnesium in the body does not decrease, but the serum levels do. The most common causes of low magnesium in these cases are:
“Hungry bone syndrome”
Refeeding syndrome (a serious and life-threatening complication that happens when people who are malnourished start eating again)
Insulin treatment
Correction of diabetic ketoacidosis with alkali therapy
Massive blood transfusions
Side effects of drugs called beta-agonists (asthma drugs) or epinephrine
RELATED: 9 common nutrient deficiencies in the U.S.
Low magnesium is estimated to affect about 2% of the population, but some people are at far greater risk than others. The most common risk factors include:
Poor nutrition
Chronic alcohol use
Critical or chronic illness
Hospitalization
Pregnancy
Gastrointestinal disorders
Chronic use of a type of stomach acid reducer called a proton pump inhibitor
Continued use of certain types of diuretics (“water pills”)
Low magnesium levels are a potentially serious medical condition. Severe low magnesium can cause dangerous, and even fatal, heart rhythm problems. It’s not just low magnesium that may be a problem. Hypomagnesemia causes low potassium levels (hypokalemia), low calcium levels (hypocalcemia), low phosphate levels (hypophosphatemia), and vitamin D deficiency. All of these have their own possibly serious complications.
Low magnesium and other electrolyte disorders often don’t have symptoms, so regular healthcare visits are important. This is especially true for people at risk of low magnesium, such as anyone with Type 2 diabetes. Routine blood tests are usually the first and only way that people find out they have an electrolyte abnormality like low magnesium.
See a healthcare professional if there are symptoms of low magnesium or any other electrolyte disturbance. Call 911 or go to an emergency if there are severe symptoms of hypomagnesemia, such as abnormal heartbeats, racing heartbeats, or seizures.
Healthcare professionals diagnose low magnesium levels with a blood test. They will measure serum magnesium and other electrolyte levels, particularly potassium and calcium. A urine test may be used to see if magnesium and other electrolytes are being excreted through the kidneys. If there’s any suspicion that the heart is affected by low magnesium, the clinician will order an electrocardiogram (EKG) to identify any heart rhythm abnormalities.
Some hereditary conditions cause low magnesium, but they’re very rare. All are associated with particular genetic mutations that can be passed onto offspring only if both parents have the gene responsible for the hereditary condition.
RELATED: Why is family health history important?
Depending on the cause and severity of low magnesium, the problem can usually be corrected with magnesium supplements. People may be asked to take calcium and potassium supplements as well. Severe low magnesium is treated with intravenous magnesium sulfate solution. The underlying cause may require separate treatment.
RELATED: Which magnesium supplement is right for me?
There are two ways to prevent low magnesium.
The first is to ensure that you have enough magnesium in your diet. The recommended daily allowance for young adults is 400 mg for men and 310 mg for women. The recommended daily allowance for adults older than 30 years of age is 420 mg for men and 320 mg for women. Getting each day’s recommended daily allowance of magnesium can be accomplished by:
Eating magnesium-rich foods, such as seeds, nuts, cashews, whole grains, cereals, and beans
Taking magnesium supplements or multivitamins with magnesium
The second way to prevent low magnesium is to manage any medical condition that may cause low magnesium, such as diabetes, alcohol use, or gastrointestinal diseases:
Take all medications as prescribed by a healthcare professional
Follow the diet recommended by healthcare providers
Take recommended or prescribed dietary supplements
Visit the doctor regularly to have your blood tested for electrolyte levels
Avoid drinking alcohol
Contact a doctor if symptoms of an electrolyte imbalance are experienced
For most people, low levels of magnesium are not usually worrisome. A normal diet is enough to prevent hypomagnesemia. However, people should be concerned if they’re at risk for low magnesium. Diabetes, chronic digestive system problems, drinking alcohol, and pregnancy are all conditions that profoundly increase the risk of low magnesium and other electrolyte imbalances. In these cases, eat a healthy diet with foods that are good sources of magnesium. You may want to add dietary supplements containing important minerals as well. However, ask a healthcare professional for medical advice first.
RELATED: What vitamins should I take?
Hypomagnesemia, Merck Manual (2023)
Hypomagnesemia, StatPearls (2022)
Low magnesium symptoms: What are the early signs of low magnesium?, SingleCare (2023)
Magnesium fact sheet for healthcare professionals, National Institutes of Health (2022)
Magnesium metabolism and its disorders, The Clinical Biochemist Reviews (2003)
Hypomagnesemia, StatPearls (2022)
Hypomagnesemia, Merck Manual (2023)
Associations of hypomagnesemia in patients seeking a first treatment of alcohol use disorder, Drug and Alcohol Dependence (2023)
Hypomagnesemia in critically ill patients, Journal of Intensive Care (2018)
Diabetes treatments and medications, SingleCare (2023)
What causes low potassium?, SingleCare (2020)
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