The Biomarker Handbook is a curated series that seeks to provide readers with insights on each biomarker we cover in our blood test packages and its relation to our body.
Magnesium is one of the most abundant electrolytes in the human body. It is necessary for many biological processes at an enzymatic level, RNA and DNA synthesis, energy production, blood pressure regulation, and insulin metabolism, among other bodily functions.
Magnesium is also essential for the transport of potassium and calcium between cell membranes, which ensures that processes such as nerve transmission, muscular contraction, and cardiac rhythm, are maintained.
Most magnesium, about 99% of the total body amount, is contained intracellularly in muscles, soft-tissue, and bones, this last having approximately 60% of it. The remaining 1% magnesium is located extracellularly in red blood cells and serum.
Physiologically, body magnesium is controlled via three mechanisms: intestinal absorption of orally ingested magnesium, renal reabsorption and excretion through urine, and exchange of magnesium contained in the bones.
When magnesium intake exceeds the daily needs of the body, it gets excreted through urine. In case of magnesium deprivation, the kidneys increase magnesium reabsorption to maintain adequate levels. However, pathological conditions that affect kidney filtration, such as diabetes or chronic kidney disease, can alter urinary magnesium levels, limiting the value of the urinary measure of magnesium as a test.
However, even with its restrictions, the amount of magnesium measured in a 24-hour urine test can be useful in cases where is necessary to determine whether dietary magnesium intake is adequate because the excretion of this electrolyte through the kidneys diminishes in response to deficient magnesium levels.
The distribution of magnesium in the body also makes it difficult to assess its exact values through blood and serum tests. Nevertheless, there is not a single method that can yet be considered completely satisfactory to correlate intracellular and extracellular magnesium levels.
Therefore, even some limitations may apply, the most rapid and valuable test to evaluate magnesium levels is serum magnesium concentration. Under normal conditions, serum magnesium concentrations in adults range from 0.76 to 1.15 mmol/L (1.7 to 2.3 mg/dL).
Any method used to assess magnesium levels must always be correlated with a thorough physical exam and symptoms analysis.
Signs and Symptoms of Magnesium Imbalance
Magnesium deficiency (hypomagnesemia) or excess (hypermagnesemia) is rare. However, when present, it can produce few to no symptoms if its mild to moderate. If the abnormality in magnesium levels persists in time or if it becomes severe, neuromuscular symptoms like tremors, nausea, hyporexia or anorexia, confusion, dizziness, fatigue, muscle cramps, cardiac arrhythmias, seizures, or coma can occur.
Hypomagnesemia can be seen when malnutrition, excessive renal excretion, or conditions that cause gastrointestinal malabsorption, are present. Examples of these conditions include chronic diarrhoea, alcoholism, malabsorption, and chronic stress.
Hypomagnesemia has been associated to diseases such as osteoporosis, type 2 diabetes mellitus, insulin resistance, pulmonary disease, hypertension, attention deficit hyperactivity disorder, depression, migraine headaches, Alzheimer’s disease, and cardiovascular disease. Therefore, magnesium levels can help diagnose the severity of kidney disorders, diabetes, and several gastrointestinal conditions.
On the other hand, hypermagnesemia can exceptionally appear as consequence of excessive oral ingestion of antacids or laxatives containing magnesium, in cases of impaired renal excretion as in individuals with severe renal insufficiency, and in pregnant women receiving magnesium sulfate as an anticonvulsant for severe preeclampsia or eclampsia.
Ways to Balance Magnesium Levels
Depending on the severity of clinical manifestations, is the preferred way of magnesium repletion. In asymptomatic individuals, magnesium can be given orally. In severe cases of hypomagnesemia, or as part of the treatment for preeclampsia, intravenous magnesium sulfate is used.
Magnesium can be found in many foods and beverages, including green vegetables, legumes, whole grains, fruits, seeds, nuts, fish, meat, milk, and tap water. Magnesium is usually also added to bottled water and fortified foods like breakfast cereals.
Most experts conclude that the amount of magnesium intake through supplements should be based on the body weight. These supplements are available in a variety of presentations such as magnesium citrate, magnesium chloride, magnesium oxide, magnesium lactate, and magnesium orotate, among others. On average 30% to 40% of the consumed magnesium is absorbed by the body.
Hypermagnesemia treatment usually consists of withdrawing the source of magnesium, along with calcium supplementation, diuretics, and in some cases, hemodialysis.
When is it Necessary to Test for Magnesium Levels and Other Related Ailments?
Magnesium screening is not usually indicated in all individuals, and is often not ordered alone, but rather with other electrolytes such as sodium, calcium, potassium, bicarbonate, phosphorus, and chloride. This happens because numerous studies have shown a correlation between magnesium deficiency and changes in these other electrolytes, especially calcium and potassium.
Magnesium is ordered when a person is presenting signs and symptoms that are compatible with hypomagnesemia or hypermagnesemia. It can also be ordered when a blood panel shows unexplained hypocalcemia (low calcium levels), and in cases where hypokalemia (low potassium levels) is unresponsive to potassium supplements.
Other indications for magnesium screening include individuals who have cardiac disorders that can prove to be fatal in case of developing hypomagnesemia, individuals who are taking high-dose diuretics, pregnant women with severe preeclampsia or eclampsia who are receiving magnesium sulfate as an anticonvulsant, and individuals with uncontrolled diabetes or kidney disorders.
Magnesium is one of the main electrolytes present in the body, its closely correlated to other electrolytes such as sodium, potassium, and calcium. Therefore, it shouldn’t be screened alone, but rather taking into consideration all other electrolyte parameters and the individual’s clinical situation.
Serum magnesium concentration is the most commonly used test to assess the amount of body magnesium. However, it has its limitations due to the distribution of magnesium in the body (only 1% of the body’s total magnesium is located extracellularly in the serum and red blood cells).
The onset of hypomagnesemia, or less frequently, hypermagnesemia, can prove fatal if left untreated. A great variety of foods contain magnesium, and healthy individuals with normal kidney function should be capable of maintaining normal levels of this electrolyte by having a balanced diet.
If you want to find out more about magnesium and how to maintain healthy levels of it, take a look at our lifestyle article here!
Interested in other biomarkers? Check out the rest of The Biomarker Handbook.
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