All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
Magnesium in the blood
Medical expert of the article
Last reviewed: 05.07.2025
Magnesium is the fourth most abundant element in the human body after potassium, sodium, calcium, and the second most abundant element in the cell after potassium. The human body contains approximately 25 g of magnesium, 60% of which is found in bone tissue, and most of the remaining reserve is in cells. Only 1% of all magnesium is found in the extracellular fluid. Approximately 75% of serum magnesium is in ionized form, 22% is bound to albumin, and 3% is bound to globulins. Magnesium plays an important role in the functioning of the neuromuscular system. The highest magnesium content is in the myocardium. Physiologically, magnesium is a calcium antagonist; its deficiency in serum is accompanied by an increase in calcium content. The higher the metabolic activity of a cell, the more magnesium it contains. The concentration of ionized magnesium in a cell is maintained at a constant level even with large fluctuations in its extracellular fluid.
[ 1 ], [ 2 ], [ 3 ], [ 4 ], [ 5 ], [ 6 ], [ 7 ], [ 8 ], [ 9 ]
Normal concentration of magnesium in blood serum
Age |
Serum magnesium concentration |
|
Meq/L |
Mmol/l |
|
Newborns |
1.0-1.8 |
0.5-0.9 |
5 months - 6 years |
1.32-1.88 |
0.71-0.95 |
6-12 years |
1.38-1.74 |
0.69-0.87 |
12-20 years |
1.35-1.77 |
0.67-0.89 |
Adults |
1.3-2.1 |
0.65-1.05 |
Magnesium is a cofactor of a number of enzymatic reactions, it acts as a physiological growth regulator, maintaining the supply of purine and pyrimidine bases. Magnesium is necessary at all stages of protein synthesis.
The main regulator of maintaining the concentration of magnesium in the blood serum is the kidneys. In a healthy person, the daily excretion of magnesium is approximately 100 mg. When magnesium reserves are depleted, its excretion decreases or stops completely. Excess magnesium is quickly removed by the kidneys. Magnesium passes through the glomerular membrane, 80% of it is reabsorbed in the proximal tubules of the ascending segment of the loop of Henle. Large doses of PTH contribute to a decrease in the excretion of magnesium in the urine (glucagon and calcitonin have the same effect). Vitamin D and its metabolites increase the absorption of magnesium in the small intestine, but to a lesser extent than calcium.