Magnesium is an important mineral and nutrient. Doctors usually diagnose a magnesium deficiency, or hypomagnesemia, if there are low levels of magnesium in the blood.

Doctors define hypomagnesemia as a blood serum magnesium level of less than 0.75 millimoles per liter (mmol/l). They can measure this using a blood test.

Hypomagnesemia does not always cause symptoms, but some early ones can include muscle twitching, numbness, and tingling. Without treatment, hypomagnesemia can cause health problems and reduce the body’s levels of calcium and potassium.

In this article, we take a close look at what factors can cause low levels of magnesium. We also explore the effects of a magnesium deficiency on the body and methods of treatment.

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Hypomagnesemia is the medical name for a magnesium deficiency.

Magnesium is involved in more than 300 of the body’s enzyme reactions. It contributes significantly to the:

  • health of muscles and nerves
  • regulation of blood pressure
  • production of energy in the body’s cells
  • synthesis of DNA and RNA

However, the body cannot produce magnesium, so a person has to get it from their diet. If they do not get enough, or an underlying health issue affects the absorption or use of this nutrient, the person may develop hypomagnesemia.

Around 48% of people in the United States do not get enough magnesium from their diets. However, it is relatively uncommon for a low magnesium intake to cause symptoms in healthy people.

When someone has levels that are low, but not low enough to constitute a deficiency, this is called “magnesium inadequacy.”

People with mild hypomagnesemia may have no symptoms. If symptoms arise, they may include:

  • twitches, particularly in the facial muscles
  • weakness and exhaustion
  • nausea and vomiting
  • personality changes
  • tremors
  • very pronounced reflexes
  • constipation

A more severe magnesium deficiency can cause:

  • muscle contractions
  • seizures
  • changes in the heart’s rhythm

In a 2019 review, researchers noted that low blood magnesium could increase the risk of cardiovascular disease and atrial fibrillation, a disorder that causes the upper heart chambers to become uncoordinated as they beat.

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A true magnesium deficiency usually does not develop in people who are otherwise healthy. This is because the kidneys can control how much of this mineral they excrete through urine. If the body does not have enough magnesium, the kidneys can stop getting rid of the magnesium that the body does have, helping to balance the levels.

A person may develop hypomagnesemia if:

  • They consistently get too little magnesium from their diet.
  • Their kidneys excrete too much magnesium.
  • They have another medical condition that affects nutrient absorption.

Certain groups have a risk of magnesium inadequacy, which is a milder condition. This includes people affected by:

  • Malnutrition: Starvation, anorexia, bulimia, or frequent vomiting for any reason can result in a magnesium deficiency.
  • Digestive diseases: People with conditions such as Crohn’s disease, celiac disease, or regional enteritis can have difficulty absorbing magnesium via the gut. If a person has surgery to bypass the small intestine, this can also lead to magnesium loss.
  • Diarrhea: Chronic diarrhea can lead to an imbalance of electrolytes. People with gastrointestinal conditions that cause diarrhea have a greater risk of hypomagnesemia.
  • Alcohol abuse: Excessive alcohol consumption can lead to imbalances in electrolytes or nutrients, and it may cause the body to release more magnesium than usual.
  • Breastfeeding or pregnancy: Both increase the need for magnesium. During pregnancy, an adult’s magnesium needs increase from 310–320 milligrams (mg) to 350–360 mg per day. For a pregnant teenager, this requirement is up to 400 mg daily.
  • Age: It becomes more difficult to absorb magnesium with time, putting older adults at a higher risk of magnesium inadequacy.
  • Diabetes: If a person has type 2 diabetes or insulin resistance, high levels of glucose in the kidneys can cause the body to excrete more magnesium. Diabetic ketoacidosis is a life-threatening complication of diabetes, and it can reduce magnesium levels, too.
  • Organ failure: Organ failure, particularly of the kidneys, may cause the body to excrete too much magnesium.

People taking certain medications may also lose large amounts of magnesium. These medicines include:

  • some antifungal drugs
  • diuretics
  • proton pump inhibitors
  • the chemotherapy drug cisplatin

Taking certain thyroid hormones may have a similar effect.

The body contains approximately 25 grams (g) of magnesium, more than half of which is in the bones. Magnesium is also abundant in the soft tissues. Less than 1% of the body’s magnesium is in serum, the fluid component of blood.

In the blood, normal serum magnesium levels range from 0.75 to 0.95 mmol/l. Doctors diagnose hypomagnesemia when an individual has a serum magnesium level of less than 0.75 mmol/l.

A blood test can confirm the diagnosis. If there is no apparent cause, the doctor can find out if the person is losing magnesium through their kidneys or digestive system. They can measure the amount of magnesium in the person’s urine over 24 hours.

Doctors treat low magnesium levels in different ways, depending on the situation.

Mild cases

For mild magnesium inadequacy in people with no other health problems, a doctor may suggest getting more magnesium from the diet. The following foods contain high amounts of magnesium:

FoodMagnesium per serving% of the recommended daily allowance (RDA) for males% of the RDA for females
1 ounce of almonds76.5 mg19.13%23.9%
1 avocado39.4 mg9.85%12.31%
1 cup cooked brown rice78.8 mg19.7%24.63%
1 cup raw lentils90.2 mg22.55%28.19%
1 cup cooked oats60.8 mg 6.5%8.13%

If eating magnesium-rich foods is not an option or does not help, a doctor may suggest a magnesium supplement. However, anyone with a kidney condition must use these with caution.

If the kidneys are not functioning well, they may not excrete any surplus magnesium at a typical rate, leading to the opposite problem — hypermagnesemia. This is when the body has too much magnesium.

Learn more about hypermagnesemia.

Severe cases

If someone has more significant hypomagnesemia, a doctor may treat it by giving a high dose of magnesium over a period of time.

For example, if someone develops this condition in the hospital, a doctor may administer 1–2 g of magnesium in 15 minutes to quickly get the levels back up. Doctors can only do this for people who have good kidney function and an otherwise stable condition.

If a person’s magnesium levels are persistently low, the underlying cause also requires treatment. For example, if the kidneys are losing too much magnesium, a doctor may recommend amiloride, a diuretic that increases urine output while sparing potassium and magnesium.

If a deficiency is severe, a doctor may recommend injecting magnesium into a muscle or vein. Ongoing monitoring can determine whether the treatment is working.

A person with very low levels of magnesium may also have a calcium or potassium deficiency. Low calcium is known as hypocalcemia, while a potassium deficiency is called hypokalemia.

Magnesium helps transport calcium and potassium ions in and out of cells. It may also contribute to the absorption of these important minerals. This is why a lack of magnesium can lead to low calcium and potassium levels.

Treating only a magnesium deficiency can make the calcium deficiency worse, as magnesium binds to calcium.

Doctors who suspect hypomagnesemia often test for other deficiencies. This allows them to treat hypomagnesemia, hypocalcemia, and hypokalemia all at the same time, if necessary.

The outlook for someone with a magnesium deficiency depends on the cause.

If a mild case of magnesium inadequacy results from factors such as a lack of magnesium in the diet, pregnancy, or older age, eating more magnesium-rich foods or taking a supplement can often resolve the issue.

For people with more severe or persistent hypomagnesemia, a doctor must identify the cause before they can predict the outcome. If they can find and treat the root cause, a complete recovery is likely.

Receiving treatment is crucial, as dangerously low levels of this mineral can cause fatal heart conditions. It is also important that people do not self-diagnose and treat a magnesium deficiency.

A person should not take magnesium supplements, especially in high doses, without speaking to a doctor. Too much of any nutrient, including magnesium, can be harmful and cause an imbalance in levels of other nutrients.