Hypomagnesemia (Low Blood Magnesium Levels)

What is hypomagnesemia?

Hypomagnesemia is the medical term for lower than normal magnesium levels in the blood. Although magnesium is so abundant in the body and very important for health, it is often not given as much attention as calcium and phosphate. However, magnesium is just as important as these minerals and is in fact needed for calcium and phosphate to be properly utilized by the body. Recent evidence indicating that hypomagnesemia is an important side effect of prolonged use of a widely used acid-suppressing drug known as proton pump inhibitors (PPIs), has shed light on the importance of magnesium.

How common is hypomagnesemia?

The incidence of hypomagnesemia is dependent on the patient, their health stats and underlying diseases. It is estimated that 2 out of every 100 people in the general population have some degree of hypomagnesemia. It is a small but significant incidence. However, in patients who are hospitalized and especially those in the intensive care unit (ICU), the incidence is much higher. Hypomagnesemia may be as common as 20% in hospitalized patients and up to 65% in ICU patients. Alcoholics are often at the greatest risk of hypomagnesemia.

Effects of Low Blood Magnesium Levels

Magnesium is essential for homeostasis – the delicate balance that maintains health. It is the fourth most abundant mineral in the human body and about half of all the magnesium is in the bones. Most of the other half is within the cells and only about 1% of magnesium is in the blood. The diversity of functions of magnesium in the human body makes it one of the most important minerals. Magnesium is important for the proper functioning and health of the :

  • Muscles
  • Bones
  • Heart and blood vessels
  • Immune system
  • Blood glucose levels
  • Energy production
  • Protein synthesis

In addition, magnesium affects the potassium levels in the blood and hypomagnesemia can lead to hypokalemia (low blood potassium). Therefore low blood magnesium levels will cause a range of disturbances in these organs and systems. Some of the major consequences of hypomagnesemia are briefly discussed below.

Heart rhythm

Abnormalities in rhythm of the heart contraction and relaxation is known as an arrhythmia. Hypomagnesemia is recognized as an important cause of arrhythmias. It affects the electric system of the heart, contraction of the heart muscle and tone of the blood vessels. Hypomagnesemia also heightens the effects of drugs like digitalis on the heart.

Blood pressure

Blood pressure is dependent on several factors such as the force of the heart contraction, volume of blood and the resistance of the blood vessels. Low blood magnesium levels by causing an increase of calcium levels within the cells leads to increased peripheral resistance. This means that blood has to be pushed harder and the blood pressure increases (hypertension).

Nerves and Muscles

The nerves and muscles in the body are affected in several ways when the blood magnesium levels are low. The speed of the nerve impulses are slower than normal and both the nerves and muscles are more excitable. This leads to various neuromuscular manifestations such as seizures, muscle cramps, hyperreactive reflexes, depression, nausea and vomiting. It has also been suggested that a magnesium deficiency contributes to premenstrual syndrome (PMS) but whether this is a neurological manifestation or related to a hormone imbalance is not always clear.


Magnesium is an important contributor to bone mass density and therefore bone strength. It affects calcium which is essential for bone mineralization. Therefore magnesium is an important mineral to be consumed in conjunction with calcium supplementation for people who are at a high risk of osteoporosis, such as postmenopausal women.


It appears that the presence of  magnesium plays an important role in preventing the various components of urine from precipitating and crystallizing. Therefore it prevents the formation of urinary stones. However, it is important to note that excessive supplementation of various minerals may in fact contribute to urinary stones.

Blood Sugar

Hypomagnesemia can affect the regulation of blood glucose levels but this may be more prominent in diabetes than those with normal glucose tolerance. Lower than normal magnesium levels affect the sensitivity and secretion of insulin. As yet it has not been conclusively proven that a magnesium deficiency is a contributing factor to the development of diabetes mellitus.

Signs and Symptoms

The signs and symptoms of hypomagnesemia depends on the organ or system affected by the magnesium deficiency. Therefore the symptoms can vary to some extent from one person to another. Blood tests are the most conclusive way to identify a magnesium deficiency. Some of the signs and symptoms of hypomagnesemia therefore includes :

  • Abnormal sensations particularly on the hands and legs known as paresthesias.
  • Muscle weakness, twitching, cramps and tremors.
  • Seizures (convulsions).
  • Rapid abnormal eye movements known as nystagmus.
  • Abnormalities on ECG (electrocardiogram).
  • High blood pressure (hypertension).
  • Side effects when using digitalis indicating toxicity despite the use of controlled therapeutic amounts.
  • Nausea and vomiting.

Hypomagnesemia also contributes to low blood potassium levels (hypokalemia) and low blood calcium levels (hypocalcemia). Therefore the signs and symptoms of these mineral deficiencies may also be present.

Causes of Magnesium Deficiency

Magnesium is acquired through the diet. Therefore a diet deficient in magnesium will contribute to hypomagnesemia. However, there may be sufficient intake of foods rich in magnesium but defective absorption from the gut hampers the uptake of magnesium. The levels of magnesium in the body are regulated and large amounts are eliminated through the kidneys into the urine. Kidney disorders can therefore contribute to higher than normal magnesium loss thereby leading to a deficiency despite normal intake and absorption.Magnesium may also be lost through the stool, perspiration and vomitus. Only 1% of the body’s magnesium is circulating in the bloodstream. Therefore certain conditions can draw out the magnesium from the blood into bone and tissue, leaving the circulating magnesium levels lower than normal.

Risk Factors for Hypomagnesemia

There are various possible causes of a magnesium deficiency. However, not every person with these conditions will experience hypomagnesemia and it largely depends on the duration and severity of the underlying condition. People who are at a greater risk of developing hypomagnesemia may include those with one or more of the following conditions :

  • Alcoholism and alcohol withdrawal syndrome.
  • High aldosterone levels (hyperaldosteronism).
  • High calcium levels in the blood (hypercalcemia).
  • Celiac disease.
  • Diabetic ketoacidosis treatment.
  • Diarrhea that is long standing.
  • Hungry bone syndrome.
  • Inflammatory bowel disease (IBD)
  • Acute kidney failure.
  • Medication such as certain antibiotics, proton pump inhibitors (PPIs), diuretics, immunosuppressants and cancer drugs (chemotherapy).
  • Acute pancreatitis.
  • Total parenteral nutrition where a person is fed through an IV drip entirely.
  • Polyuria (excessive urination).
  • Starvation and malnutrition.
  • Excessive sweating.
  • Profuse and prolonged vomiting.

Tests and Diagnosis

The signs and symptoms of hypomagnesemia are non-specific for magnesium deficiency. Therefore various tests needs to be conducted to confirm a diagnosis of hypomagnesemia. Blood and urine tests may reveal low magnesium levels when hypomagnesemia is suspected. Sometimes the presence of abnormalities in blood potassium and calcium may be an indicator of hypomagnesemia. Therefore it is advisable to conduct a blood magnesium test simultaneously.

Video on Testing for Magnesium Deficiency

It is important to note that a magnesium deficiency may not be immediately evident as hypomagnesemia.

Hypomagnesemia Treatment

It is important to identify the underlying cause of hypomagnesemia in order treat it effectively. Simply supplementing with magnesium will not resolve hypomagnesemia if the underlying condition is also not treated appropriately. Babies need at least 80mg of magnesium per day while adult males over the age of 30 years may need as much as 420mg per day. Hypomagnesemia is treated with magnesium supplements such as magnesium oxide, magnesium gluconate and magnesium sulfate. These supplements may be admagnesministered orally (through the mouth) or intravenously (into the veins). In addition a patient is administered IV fluids and certain types of “water pills” known as potassium-sparing diuretics to prevent the loss of potassium through the kidneys. These diuretics help to quickly restore the blood potassium levels which may have been low due to the magnesium deficiency.

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